Title of Invention	"H-BRIDGE INVERTER FOR ALTERNATING CURRENT MOTOR"
Abstract	An H-bridge inverter for an alternating current motor is disclosed, in which output voltages of power cells can be output by allowing cell controllers to compensate input voltages of the power cells even in case that the input voltages are varied. A user can select an operation mode of each cell controller as a compensation mode for the input voltage and an output voltage control mode according to simple command frequency. Since the cell controller has a compensation control function for variation of the input voltage, it is possible to reduce communication load between a master controller and the cell controller.

Title of Invention

"H-BRIDGE INVERTER FOR ALTERNATING CURRENT MOTOR"

Abstract

An H-bridge inverter for an alternating current motor is disclosed, in which output voltages of power cells can be output by allowing cell controllers to compensate input voltages of the power cells even in case that the input voltages are varied. A user can select an operation mode of each cell controller as a compensation mode for the input voltage and an output voltage control mode according to simple command frequency. Since the cell controller has a compensation control function for variation of the input voltage, it is possible to reduce communication load between a master controller and the cell controller.

Full Text	H-BRIDGE INVERTER FOR ALTERNATING CURRENT MOTOR BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to driving control of an alternating current motor which is used as a driving power source of an industrial high power equipment such as a pump, a fan, a compressor, a mixer, and a conveyer and requires a power source of a high voltage. Specifically, the present invention relates to a high voltage inverter having an output voltage of 2 kilo volt (KV) to 5KV, and more particularly, to a high voltage inverter that can obtain a high output voltage by connecting a plurality of low voltage inverters (for example, inverters having an output voltage of 200V or 400V) in series per phase of three phases. More specifically, the present invention relates to an inverter system that can be distributive controlled by cell controllers and a master controller, wherein the cell controllers are for individual control per power cell and the master controller is for controlling the cell controllers. More specifically, the present invention relates to a high voltage inverter system in which an output voltage is not affected by variation of an input voltage of each power cell. More specifically, the present invention relates to a high voltage inverter system in which cell controllers can prevent an output voltage from being affected by variation of an input voltage of each power cell without depending on a master controller. 1A More specifically, the present invention relates to a high voltage inverter system that uses serial communication for communication between a master controller and a plurality of cell controllers and more specifically uses a controller area network (CAN) communication. 2. Description of the Background Art An H-bridge inverter system which is a kind of a high voltage inverter system comprises an individual power source per power cell to supply a direct current power source to each power cell. A transformer is used for individual power supply. A rectifier and a capacitor are used to convert an alternating current supplied from the transformer into a direct current and thus supply the direct current to a semiconductor switch in the power cell. A voltage rectified by the rectifier and smoothed by the capacitor is detected from both ends of the capacitor and at the same time is an input voltage of the power cell. This voltage is so called as a DC-link voltage in the related art. However, the DC-link voltage per power cell may be varied due to voltage variation of an input alternating current power source of the transformer, i.e., a commercial alternating current power source. This does not allow an inverter to output an output voltage requested from an alternating current motor. Furthermore, several DC-link voltages for power cell may be different from other DC-link voltages for power cell due to percent impedance voltage drop of the transformer, i.e., a secondary output voltage error of the transformer or the difference in individual capacitance of the capacitor. For this reason, unbalance may occur between output voltages of the inverter per phase. This causes an over 2 voltage to a semiconductor switch of a specific phase during regeneration, whereby the corresponding semiconductor switch may be burned. To solve the above problem, the power cell may be connected to a circuit breaker so that the circuit breaker may be tripped when the over voltage occurs so as to protect the power cell. However, problems occur in that if the circuit breaker connected to the power cell of one phase is tripped, voltages applied to the power cells of other phases increase and the operation of a load device such as motor may stop as the operation of the inverter stops. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an H-bridge inverter for an alternating current motor, in which output voltages of power cells and a final output voltage of the inverter are not affected even by lump variation or individual variation of DC-link voltages for a plurality of power cells. Another object of the present invention is to provide an H-bridge inverter for an alternating current motor, in which a plurality of cell controllers not a master controller can control respective power cells so as not affect output voltages of the power cells, thereby reducing computation load and communication load of the mater controller. To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided an H-bridge inverter for an alternating current motor, which comprises a plurality of power cells connected in series per three phases, each having a semiconductor switch, a rectifying circuit and a smoothing condenser, the 3 semiconductor switch capable of switching controlled, and the rectifying circuit and the smoothing condenser for supplying a DC-link voltage to the semiconductor switch as an input voltage; a phase shift transformer having a primary winding and a plurality of secondary windings, the secondary windings being connected to each of the power cells to supply an individual three-phase alternating current power source; a master controller providing an output frequency command signal depending on a predetermined speed command, the output frequency command signal representing an output frequency of the inverter; a plurality of cell controllers communicatively connected to the master controller and each provided correspondingly to each of the power cell, for determining an input voltage to output voltage rate of each power cell as a rate of a command frequency according to the output frequency command signal from the master controller in comparison with a predetermined rated frequency of the alternating current motor, for generating a reference voltage depending on the rated voltage of the alternating current motor, for computing a compensation voltage according to the input voltage to output voltage rate with respect to the difference between the reference voltage and the detected DC-link voltage, for compensating the computed compensation voltage for the reference voltage, and for generating a pulse width modulation signal having a pulse width determined depending on the compensated reference voltage to control switching of the semiconductor switch in the power cell; and a network connected between the master controller and the cell controllers, for providing a communication path between the master controller and the cell controllers. The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed 4 description of the present invention when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings: Figure 1 is a block diagram illustrating the whole configuration of an H-bridge inverter for an alternating current motor according to the present invention; Figure 2 illustrates is a block diagram illustrating communication between a mater controller and cell controllers in an H-bridge inverter for an alternating current according to the present invention; Figure 3 is a block diagram illustrating the detailed configuration of a cell controller of an H-bridge inverter for an alternating current motor according to one embodiment of the present invention; Figure 4 is a block diagram illustrating the detailed configuration of a cell controller an H-bridge inverter for an alternating current motor according to another embodiment of the present invention; Figure 5 is a waveform illustrating a method for modulating a pulse width of a pulse width modulation signal generator included in a cell controller of an H-bridge inverter for an alternating current motor according to the present invention; Figure 6 is a flow chart illustrating the operation of a cell controller of an H-bridge inverter for an alternating current motor according to one embodiment of 5 the present invention; and Figure 7 is a flow chart illustrating the operation of a cell controller of an H-bridge inverter for an alternating current motor according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Figure 1 is a block diagram illustrating the whole configuration of an H-bridge inverter for an alternating current motor according to the present invention. As shown in Figure 1, the H-bridge inverter for an alternating current motor according to the present invention comprises a phase shift transformer 71. The phase shift transformer 71 comprises a primary winding 71A and a plurality of secondary windings 71B1-71Bn. The primary winding 71A is formed of a three-phase delta winding which receives a three-phase AC power source, for example AC 220V and a frequency of 60Hz. The secondary windings 71B1~71Bn transform the voltage, for example, AC 220V of the primary winding 71A into 24V and provide the 24V to each of power cells U1~Un, V1~Vn, W1~Wn and are formed of delta windings. TAB is a center tap provided between the primary winding 71A and the secondary windings 71B1~71Bn. U-phase power cells U1~Un, V-phase power cells V1-Vn and W-phase power cells W1~Wn are connected in series per phase so that the sum of output voltages of the power cells connected in series per phase is provided to an alternating current motor 73 as each output voltage of corresponding phases U, V 6 and W. As described above, the alternating current motor 73 is used as a driving power source of an industrial high power equipment such as a pump, a fan, a compressor, a mixer, and a conveyer, and requires a power source of a high voltage of 2KV to 5KV. As shown in a dotted line block of Figure 1 illustrating an enlarged inner configuration of the W-phase nth power cell Wn as an example of the power cells U1~Un, V1~Vn, W1~Wn, each of the power cells U1~Un, V1~Vn, W1~Wn according to the present invention comprises a rectifying circuit CON and a capacitor C, wherein the rectifying circuit CON rectifies any one of three-phase alternating currents among the secondary windings 71B1~71Bn to a direct current, and the capacitor C smoothes the direct current rectified by the rectifying circuit CON and provides the smoothed direct current to a semiconductor switch SW. A voltage across the capacitor C is an input voltage provided to the power cells U1~Un, V1~Vn, W1~Wn, in more detail an input voltage provided to the semiconductor switch SW in the power cells U1~Un, V1~Vn, W1~Wn. Hereinafter, the voltage will be referred to as a DC-link voltage. For example, the semiconductor switch SW means for example an insulated gate bipolar transistor (IGBT) or a silicon control rectifier (SCR) that can . be turned on or off by a gate driving signal, i.e., an output signal of a pulse width modulation signal generator in the inverter of the present invention. Each of the power cells U1~Un, V1~Vn, W1~Wn is a low voltage inverter for driving the alternating current motor 73 by inverting the input voltage, i.e., the DC-link voltage of the capacitor C to an alternating current voltage. To control each of the power cells U1-Un, V1~Vn, W1~Wn, the number of cell controllers U1CC1~UnCCn, V1CC1~VnCCn, W1CC1~WnCCn corresponds 7 to the number of the power cells U1~Un, V1~Vn, W1~Wn, and the cell controllers are respectively connected to the power cells U1~Un, V1~Vn, W1~Wn. The mater controller 72 controls all the cell controllers U1CC1~UnCCn, V1CC1~VnCCn, W1CC1~WnCCn, and provides an output frequency command signal in accordance with a predetermined speed command, wherein the output frequency command signal represents an output frequency of the inverter, i.e., the power cells U1~Un, V1~Vn, W1~Wn. The predetermined speed command means speed command data stored in a program memory means such as a read only memory (ROM) set on a program input by a program input means such as a program loader, which can be connected to the master controller 72 by a data transmission line. The master controller 72 may have control functions such as restarting after instantaneous power failure, motor speed search, emergency stop, automatic energy saving, self diagnosis, and automatic tuning. However, since such control functions of the master controller 72 have nothing to do with the present invention, their detailed description will be omitted. The master controller 72 is connected with the cell controllers U1CC1~UnCCn, V1CC1~VnCCn, W1CC1~WnCCn through a communication network N to enable mutual communication. The data transmitted from the master controller 72 to the cell controllers U1CC1~UnCCn, V1CC1~VnCCn, W1CC1~WnCCn may include information such as an output voltage command, a synchronizing signal, motor overheating, transformer overheating, fan error, and output phase deficiency. The data transmitted from the cell controllers U1CC1~UnCCn, V1CC1~VnCCn, W1CC1~WnCCn to the master controller 72 may include information such as over voltage, shortage voltage, over current, arm 8 short of the semiconductor switch, earth leakage, phase deficiency of the power cell. Since such data have nothing to do with the present invention, their detailed description will be omitted. As shown in Figure 2, communication between the master controller 72 and the cell controllers U1CC1~UnCCn, V1CC1~VnCCn, W1CC1~WnCCn is realized by the communication network N. Preferably, an example of the communication network N comprises an optic fiber cable having fast data transmission speed and good insulation property to noise. Furthermore, communication networking between the master controller 72 and the cell controllers U1CC1~UnCCn, V1CC1~VnCCn, W1CC1~WnCCn uses a Controller Area Network (CAN) having excellent characteristics in view of fast data transmission and insulation to noise. Referring to Figure 2, blocks of the CAN shown in the master controller 72 represent the configuration that enables CAN communication in the master controller 72. Also, in Figure 2, the communication network N extended to the master controller 72 is comprised of an optic connector coated with an insulating material on an optic fiber. In addition to the above configuration, CAN drivers may separately be connected to the outside of the master controller 72 and the cell controllers U1CC1~UnCCn, V1CC1~VnCCn, W1CC1~WnCCn to enable communication between the CAN drivers through the communication network N. Meanwhile, a block diagram illustrating the detailed configuration of a cell controller of an H-bridge inverter for an alternating current motor according to one embodiment of the present invention will be described with reference to Figure 3. Since the cell controllers according to the present invention have the same configuration as one another, the first cell controller U1CC1 of the U-phase 9 cell controllers U1CC1~UnCCn connected in series will be described in detail with reference to Figure 3. The cell controller U1CC1 determines an output voltage to the input voltage rate of the power cell U1 (see Figure 1) as a command frequency rate according to the output frequency command signal from the master controller 72 (see Figure 1) in comparison with a predetermined rated frequency of the alternating current motor 73. In other words, if the rated frequency of the alternating current motor is 60Hz and the command frequency according to the output frequency command signal is 30Hz, the cell controller U1CC1 determines the output voltage to the input voltage rate as 50%. The cell controller U1CC1 generates a reference voltage depending on a rated voltage of the alternating current motor 73. For example, if the rated voltage of the alternating current motor is 200V, the cell controller U1CC1 computes 20V corresponding to 10% of 200V as a reference voltage value and stores the resultant value therein. In this case, the rate of 10% is predetermined and stored. The cell controller U1CC1 computes a compensation voltage according to the output voltage to the input voltage rate with respect to the difference between the reference voltage and the detected DC-link voltage and compensates the computed compensation voltage with respect to the reference voltage. For example, since the reference voltage is 20V if the detected DC-link voltage is 18V, the difference voltage is 18V-20V=-2V and the compensation voltage is -1V obtained by multiplying the input voltage to output voltage rate corresponding to 50% by the difference voltage of -2V. The cell controller U1CC1 determines 19V obtained by adding -1V to the reference voltage of 20V as a new reference voltage in which input voltage variation is compensated. In other words, the 10 reference voltage decreases if the input voltage of the power cell, i.e., the DC-link voltage decreases, and vice versa. Although described later, increase of the reference voltage decreases a pulse width of a pulse width modulation signal for driving the semiconductor switch SW of the power cell, so as to decrease the turn-on time of the semiconductor switch, whereby the voltage supplied from the power cell to the alternating current motor decreases. On the other hand, decrease of the reference voltage increases the pulse width of the pulse width modulation signal for driving the semiconductor switch SW of the power cell, so as to increase the turn-on time of the semiconductor switch, whereby the voltage supplied from the power cell to the alternating current motor increases. Furthermore, the cell controller U1CC1 generates the pulse width modulation signal having a pulse width determined depending on the compensated reference voltage to control switching of the semiconductor switch SW in the power cell U1. In other words, the cell controller U1CC1 determines the turn-on time of the semiconductor switch SW in the power cell U1 using a pulse width of a pulse signal supplied to a gate of the semiconductor switch SW. The pulse width, as shown in Figure 5, is determined by a time period between two dotted lines, i.e., for a time period of a triangle carrier wave having a peak value of 200V greater than or equal to a reference voltage of 100V. An output signal having a rectangular output waveform of high level is output from the cell controller U1CC1 to the gate of the semiconductor switch SW in the power cell U1 for the time period. Unlike an example shown in Figure 5, the peak value of the triangle carrier wave may be 20V if the compensated reference voltage is 19V. The voltage of the reference voltage is previously computed as a voltage value having a rate predetermined depending on the rated voltage value of the 11 alternating current motor connected to the inverter and at the same time is a normal DC-link voltage, i.e., a value predetermined by a normal charge voltage of the capacitor C of Figure 1. Accordingly, there is no change in the reference voltage value unless the capacitor C is replaced with another one having different capacity and the rated voltage value of the alternating current motor is varied. Also, the peak voltage of the triangle carrier wave is predetermined as a voltage as much as the predetermined value greater than the reference voltage, and a triangle carrier wave generating circuit generating a triangle carrier wave signal having a corresponding peak voltage is previously selected. Accordingly, there is no change in the peak voltage of the triangle carrier wave unless the triangle carrier wave generating circuit is replaced with another one. In Figure 5, the peak voltage of the triangle carrier wave and the reference voltage are exemplarily suggested at 200V and 100V, respectively, not 20V and 19V, for convenience of description. Accordingly, it does not matter what the voltage values are. The output signal having a rectangular output waveform of high level can be output from the cell controller U1CC1 to the gate of the semiconductor switch SW in the power cell U1 for a time period of the triangle carrier wave greater than or equal to the reference voltage of 19V The detailed configuration of the cell controller U1CC1 according to Figure 3 and the operation of the cell controller U1CC1 will be described below. The cell controller U1CC1 comprises an output voltage rate computing unit 81. The output voltage rate computing unit 81 computes the command frequency rate according to the output frequency command signal from the master controller 72, for example, a rate of 30Hz corresponding to 50% of the 12 predetermined rated frequency, for example, 60Hz of the alternating current motor 73, and determines the rate of the output voltage of the power cell U1 with respect to the DC-link voltage as the computed rate, i.e., 50%. The cell controller U1CC1 comprises a reference voltage generator 82. The reference voltage generator 82 generates a reference voltage depending on the predetermined rated voltage of the alternating current motor. Supposing that the user previously inputs the rated voltage of 200V, the reference voltage generator 82 computes 20V corresponding to 10% of 200V and stores the computed value therein. In this case, the rate of 10% is predetermined by a manufacturer of the inverter and previously stored on a program by an input means such as a program loader The cell controller U1CC1 comprises a difference voltage computing unit 83. The difference voltage computing unit 83 computes a difference voltage between the detected DC-link voltage and the reference voltage provided from the reference voltage generator. For example, since the reference voltage is 20V if the detected DC-link voltage is 18V, the difference voltage is 18V-20V=-2V. The difference voltage computing unit 83 provides the difference voltage -2V as the resultant value. The cell controller U1CC 1 comprises a compensation voltage computing unit 84. The compensation voltage computing unit 84 obtains a compensation voltage of -1V by multiplying the rate, i.e., 50%, of the output voltage of the power cell to the DC-link voltage provided from the output voltage rate computing unit 81 by the difference voltage of -2V provided form the difference voltage computing unit 83. The cell controller U1CC1 comprises a pulse width modulation signal 13 generator 86. To control switching of the semiconductor switch SW in the power cell U1, the pulse width modulation signal generator 86 generates a pulse width modulation signal having a pulse width determined depending on a voltage of 19V obtained by compensating the compensation voltage of -1V for the reference voltage of 20V from the reference voltage generator 82. In more detail, the pulse width modulation signal generator 86 determines the turn-on time of the semiconductor switch SW in the power cell U1 using the pulse width of the pulse signal supplied to the gate of the semiconductor switch SW. The pulse width, as shown in Figure 5, is determined by a time period between two dotted lines, i.e., for a time period of a triangle carrier wave having a peak value of 200V greater than or equal to a reference voltage of 100V. An output signal having a rectangular output waveform of high level is output from the cell controller U1CC1 to the gate of the semiconductor switch SW in the power cell U1 for the time period. Unlike the example shown in Figure 5, the peak value of the triangle carrier wave may be 20V if the compensated reference voltage is 19V The output signal having a rectangular output waveform of high level can be output from the cell controller U1CC1 to the gate of the semiconductor switch SW in the power cell U1 for the time period of the triangle carrier wave greater than or equal to the reference voltage of 19V. Accordingly, the power cell U1 is turned on for the high level time period of the pulse width modulation signal from the pulse width modulation signal generator 86." Thus, the power cell U1 inverts the DC-link voltage to the alternating current voltage so as to supply the alternating current voltage to the alternating current motor 73. The operation of the cell controller of the H-bridge inverter for the 14 alternating current motor according to one embodiment of the present invention will be described briefly with reference to Figure 6. Figure 6 is a flow chart illustrating the operation of the cell controller of the H-bridge inverter for the alternating current motor according to one embodiment of the present invention. In step 1, the output voltage rate computing unit 81 of the cell controller U1CC1 computes the rate of command frequency, for example 30Hz according to the output frequency command signal from the master controller 72 to the predetermined rated frequency, for example 60Hz of the alternating current motor 73, that is 50%, and determines the rate of the output voltage of the power cell U1 to the DC-link voltage as the computed rate, i.e., 50%. In step 2, the difference voltage computing unit 83 of the cell controller U1CC1 computes the difference voltage between the detected DC-link voltage and the reference voltage provided from the reference voltage generator 82. For example, since the reference voltage is 20V if the detected DC-link voltage is 18V, the difference voltage is 18V-20V=-2V. The difference voltage computing unit 83 provides the difference voltage -2V as the resultant value. Afterwards, in step 3, the compensation voltage computing unit 84 of the cell controller U1CC1 obtains the compensation voltage of -1V by multiplying the rate, i.e., 50%, of the output voltage of the power cell to the DC-link voltage by the difference voltage of -2V provided from the difference voltage computing unit 83. In step 4, the pulse width modulation signal generator 86 of the cell controller U1CC1 generates a new reference voltage, i.e., the compensated reference voltage of 19V by adding the compensation voltage of -1V provided form the compensation voltage computing unit 84 to the reference voltage of 20V 15 provided from the reference voltage generator 82. Next, in step 5, the pulse width modulation signal generator 86 of the cell controller U1CC1 generates the pulse width modulation signal outputting the rectangular wave of high level for the time period of the triangle carrier wave greater than or equal to the new reference voltage by comparing the triangle carrier wave having a peak voltage of 20V with the new reference voltage, and provides the pulse width modulation signal to the gate of the semiconductor switch SW of the power cell U1 as a driving signal. Accordingly, the power cell U1 outputs a constant alternating current output voltage to the alternating current motor even if the input voltage of the power cell U1, i.e., the DC-link voltage is varied. Meanwhile, the operation of the cell controller of the H-bridge inverter for the alternating current motor according to another embodiment of the present invention will be described with reference to Figure 4. Since the cell controllers according to another embodiment of the present invention have the same configuration as one another, the first cell controller U1CC1 of the U-phase cell controllers U1CC1~UnCCn connected in series will be described in detail with reference to Figure 4. The cell controller U1CC1 of the H-bridge inverter for the alternating current motor according to another embodiment of the present invention is different from that according to one embodiment of the present invention in that the operation of the cell controller depends on user's selection information. Accordingly, the cell controller U1CC1 of the inverter according to another embodiment of the present invention will be described on the basis of the difference from that according to the one embodiment of the present invention to 16 avoid repeated description. The cell controller U1CC1 selectively executes any one of two control operations, which will be described below, depending on the user's selection information, i.e., selection information of an input voltage variation compensation mode or an output voltage command mode according to simple frequency command, more specifically user's selection information input during initial value setting of the inverter. First, when the user inputs the value of the rated voltage of the alternating current motor connected with the inverter during initial value setting of the inverter and at the same time the user's selection is in an input voltage variation compensation mode, the cell controller U1CC1 computes the compensation voltage according to the output voltage to the input voltage rate with respect to the difference between the reference voltage and the DC-link voltage and compensates the computed compensation voltage for the reference voltage. To control switching of the semiconductor switch in the power cell U1, the pulse width modulation signal generator generates the pulse width modulation signal having a pulse width determined depending on the compensated reference voltage. Second, when the user fails to input the value of the rated voltage of the alternating current motor connected with the inverter during initial value setting of the inverter or the user's selection is in an output voltage command mode according to simple frequency command, the cell controller U1CC1 determines the input voltage to output voltage rate of the power cell U1 as a rate of the command frequency according to the output frequency command signal from the master controller in comparison with the predetermined rated frequency of the 17 alternating current motor, and generates a second reference voltage different from the first reference voltage depending on the determined rate and a pulse width modulation signal having a pulse width determined depending on the second reference voltage. Meanwhile, the detailed configuration and operation of the cell controller according to another embodiment of the present invention will be described with reference to Figure 4. The detailed configuration and operation of the cell controller according to another embodiment of the present invention will be described on the basis of the difference from those according to the one embodiment of the present invention to avoid repeated description. The cell controller according to another embodiment of the present invention additionally comprises a selector 85 that provides an output voltage rate of the output voltage rate computing unit or the compensation voltage provided from the compensation voltage computing unit depending on a predetermined selection mode of the user. A contact point 85a inside the selector 85 is connected to the output voltage rate output from the output voltage rate computing unit depending on the predetermined selection mode, and another contact point 85b inside the selector 85 is connected to the compensation voltage output from the compensation voltage computing unit depending on the predetermined selection mode. Preferably, the switch and the contact points of the selector 85 shown in Figure 4 can be realized by selection data stored in the cell controller U1CC1 and a process program according to the selection data. The pulse width modulation signal generator 86 included in the cell 18 controller according to another embodiment of the present invention may generate the pulse width modulation signal having the pulse width determined depending on the new reference voltage obtained by compensating the compensation voltage from the compensation voltage computing unit 84 for the first reference voltage from the reference voltage generator 82 depending on the output from the selector 85. Also, the pulse width modulation signal generator 86 may generate the second reference voltage depending on the output voltage rate provided form the selector 85 and also generate the pulse width modulation signal having the pulse width determined depending on the second reference voltage. The second reference voltage is obtained by multiplying the output voltage rate by another reference voltage not the first reference voltage provided from the reference voltage generator 82, wherein the another reference voltage is the detected input voltage, i.e., the DC-link voltage and may be varied due to voltage variation of a commercial alternating current power source, the difference in capacity of the capacitor C, or the difference between secondary voltages per power cell of the phase shift transformer. Meanwhile, the operation of the cell controller of the H-bridge inverter for the alternating current motor according to another embodiment of the present invention will be described briefly with reference to Figure 7. Figure 7 is a flow chart illustrating the operation of the cell controller of the H-bridge inverter for the alternating current motor according to another embodiment of the present invention. The operation of the cell controller of the H-bridge inverter according to another embodiment of the present invention will be described with reference to the flow chart of Figure 7 and Figure 4. 19 First, the cell controller U1CC1 of the H-bridge inverter according to another embodiment of the present invention checks whether the rated voltage of the alternating current motor to be controlled by the inverter is set, i.e., whether data of the rated voltage input by the user are stored in step 10. If the rated voltage of the alternating current motor is set in step 10, the cell controller U1CC1 reads the set rated voltage value from a data memory means (not shown) such as a memory and advances to step 11. If the rated voltage of the alternating current motor is not set in step 10, the cell controller U1CC1 advances to step 12. In step 11, the cell controller U1CC1 checks, using the selector 85, whether the user's selection for the operation mode of the cell controller U1CC1 is in the input voltage variation compensation mode or the output voltage command mode according to the simple frequency command. If the operation mode of the cell controller U1CC1 has been selected in the input voltage variation compensation mode in step 11, the cell controller U1CC1 advances to step 14. Otherwise, if the operation mode of the cell controller U1CC1 has been selected in the output voltage command mode according to the simple frequency command, the cell controller U1CC1 advances to step 12. If the cell controller U1CC1 advances to step 14, the output voltage rate computing unit 81 of the cell controller U1CC1 computes the rate of the command frequency according to the output frequency command signal from the master controller in comparison with the predetermined rated frequency of the alternating current motor and determines the rate of the output voltage of the power cell to the DC-link voltage as the resultant rate. 20 Afterwards, the cell controller U1CC1 advances to step 15 so that the difference voltage computing unit 83 of the cell controller U1CC1 computes the difference voltage between the detected DC-link voltage and the reference voltage according to the rated voltage provided from the reference voltage generator 82. Then, the cell controller U1CC1 advances to step 16 so that the compensation voltage computing unit 84 of the cell controller U1CC1 obtains the compensation voltage by multiplying the output voltage rate of the power cell to the DC-link voltage provided from the output voltage rate computing unit 81 by the difference voltage provided from the difference voltage computing unit 83. Next, the cell controller U1CC1 advances to step 17 so that the pulse width modulation signal generator 86 of the cell controller U1CC1 generates the new reference voltage, i.e., the compensated reference voltage by adding the compensation voltage provided from the compensation voltage computing unit 84 to the reference voltage provided from the reference voltage generator 82. Next, the cell controller U1CC1 advances to step 17 so that the pulse width modulation signal generator 86 of the cell controller U1CC1 generates the pulse width modulation signal outputting the rectangular wave of high level for the time period of the triangle carrier wave greater than or equal to the new reference voltage by comparing the triangle carrier wave shown in Figure 5 with the new reference voltage. Afterwards, although not shown in Figure 7, the gate of the semiconductor switch in the power cell is driven for the high level time period of the pulse width modulation signal so as to turn on the semiconductor switch, whereby the DC-link voltage from the capacitor C is inverted to the alternating current and the sum of 21 the output voltages of the power cells connected in series per phase is supplied to the alternating current motor. Meanwhile, if the cell controller U1CC1 advances to step 12, the pulse width modulation signal generator 86 of the cell controller U1CC1 generates the second reference voltage depending on the output voltage rate provided from the selector 85. In this case, the second reference voltage is the detected input voltage, i.e., the DC-link voltage and may be varied due to voltage variation of the commercial alternating current power source, the difference in capacity of the capacitor C, or the difference between secondary voltages per power cell of the phase shift transformer. Also, if the DC-link voltage is less or greater than a desirable voltage level, a boost voltage of positive (+) or negative (-) set by the user may be added to the second reference voltage to generate a new second reference voltage. Afterwards, the cell controller U1CC1 advances to step 13 so that the pulse width modulation signal generator 86 of the cell controller U1CC1 generates the pulse width modulation signal having the pulse width determined depending on the newly generated second reference voltage and provides the generated pulse width modulation signal as a gate driving signal of the semiconductor switch of the corresponding power cell U1. As described above, the advantages of the present invention are as follows. According to the H-bridge inverter for an alternating current motor, the output voltages of the power cells and the final output voltage of the inverter are not affected even by lump variation or individual variation of the DC-link voltages for the power cells. 22 Also, according to the H-bridge inverter for an alternating current motor, the user can select the operation mode of the cell controller in the input voltage variation compensation mode or the output voltage command mode according to the simple frequency command. Finally, according to the H-bridge inverter for an alternating current motor, the plurality of cell controllers not a single master controller can control respective power cells so as not affect output voltages of the power cells, thereby reducing computation load and communication load of the mater controller. As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims. 23 What is claimed is: 1. An H-bridge inverter for an alternating current motor, comprising: a plurality of power cells connected in series per three phases, each having a semiconductor switch, a rectifying circuit and a smoothing condenser, the semiconductor switch capable of switching controlled, and the rectifying circuit and the smoothing condenser for supplying a DC-link voltage to the semiconductor switch as an input voltage; a phase shift transformer having a primary winding and a plurality of secondary windings, the secondary windings being connected to each of the power cells for supplying an individual three-phase alternating current power source; a master controller for providing an output frequency command signal depending on a predetermined speed command, the output frequency command signal representing an output frequency of the inverter; a plurality of cell controllers provided correspondingly with each of said power cell and connected communicatively to the master controller for determining an input voltage to output voltage rate of each power cell as a rate of a command frequency according to the output frequency command signal from the master controller in comparison with a predetermined rated frequency of the alternating current motor, for generating a reference voltage depending on the rated voltage of the alternating current motor, for computing a compensation voltage according to the input voltage to output voltage rate with respect to the difference between the reference voltage and the detected DC-link voltage, for compensating the computed compensation voltage for the reference voltage, and for generating a pulse width modulation signal having a pulse width determined 24 depending on the compensated reference voltage to control switching of the semiconductor switch in the power cell ; and a network connected between the master controller and the cell controllers, for providing a communication path between the master controller and the cell controllers. 2, The H-bridge inverter for an alternating current as claimed in claim 1, wherein the cell controller comprises: an output voltage rate computing unit for computing a rate of the command frequency according to the output frequency command signal from the master controller in comparison with the predetermined rated frequency of the alternating current motor and for determining a rate of the output voltage of the power cell to the DC-link voltage using the computed rate; a reference voltage generator for generating a reference voltage depending on a predetermined rated voltage of the alternating current motor; a difference voltage computing unit for computing a difference voltage between the detected DC-link voltage and the reference voltage provided from the reference voltage generator; a compensation voltage computing unit for obtaining a compensation voltage by multiplying the rate of the output voltage of the power cell to the DC-link voltage provided form the output voltage rate computing unit by the difference voltage provided from the difference voltage computing unit; and a pulse width modulation signal generator for generating a pulse width modulation signal having a pulse width determined depending on a reference voltage obtained by compensating the compensation voltage from the 25 compensation voltage computing unit for the reference voltage from the reference voltage generator, thereby for controlling switching of the semiconductor switch in the power cell. 3. The H-bridge inverter for an alternating current as claimed in claim 1, wherein the network is comprised of an optic fiber cable. 4. The H-bridge inverter for an alternating current as claimed in claim 1, wherein communication between the master controller and the cell controllers through the network is carried out by a Controller Area Network (CAN) communication. 5. An H-bridge inverter for an alternating current, comprising: a plurality of power cells connected in series per three phases, each having a semiconductor switch, a rectifying circuit and a smoothing condenser, the semiconductor switch capable of switching controlled, and the rectifying circuit and the smoothing condenser for supplying a DC-link voltage to the semiconductor switch as an input voltage; a phase shift transformer having a primary winding and a plurality of secondary windings, the secondary windings being connected to each of the power cells for supplying an individual three-phase alternating current power source; a master controller for providing an output frequency command signal depending on a predetermined speed command, the output frequency command signal representing an output frequency of the inverter; 26 a plurality of cell controllers provided correspondingly with said power cell and connected with the master controller communicatively for determining an input voltage to output voltage rate of the power cell as a rate of a command frequency according to the output frequency command signal from the master controller in comparison with a predetermined rated frequency of the alternating current motor, for generating a first reference voltage depending on the rated voltage of the alternating current motor if an input voltage variation compensation mode is previously selected by a user, for computing a compensation voltage according to the input voltage to output voltage rate with respect to the difference between the first reference voltage and the detected DC-link voltage, for compensating the computed compensation voltage for the first reference voltage, for generating a pulse width modulation signal having a pulse width determined depending on the compensated first reference voltage or, if an output voltage command mode according to simple frequency command is previously selected by the user, for determining the input voltage to output voltage rate of the power cell as the rate of the command frequency according to the output frequency command signal from the master controller in comparison with the predetermined rated frequency of the alternating current motor, for generating a second reference voltage depending on the determined rate and generating a pulse width modulation signal having a pulse width determined depending on the second reference voltage, thereby controlling switching of the semiconductor switch in the power cell; and a network connected between the master controller and the cell controllers, for providing a communication path between the master controller and the cell controllers. 27 6. The H-bridge inverter for an alternating current as claimed in claim 5, wherein the cell controller comprises: an output voltage rate computing unit for computing a rate of the command frequency according to the output frequency command signal from the master controller in comparison with the predetermined rated frequency of the alternating current motor and for determining a rate of the output voltage of the power cell to the DC-link voltage using the computed rate; a reference voltage generator for generating a first reference voltage depending on a predetermined rated voltage of the alternating current motor; a difference voltage computing unit for computing a difference voltage between the detected DC-link voltage and the first reference voltage provided from the reference voltage generator; a compensation voltage computing unit for obtaining a compensation voltage by multiplying the rate of the output voltage of the power cell to the DC-link voltage provided form the output voltage rate computing unit by the difference voltage provided from the difference voltage computing unit; a selector for providing the rate of the output voltage from the output voltage rate computing unit or the compensation voltage from the compensation voltage computing unit depending on a predetermined selection mode of the user; and a pulse width modulation signal generator for generating either a pulse width modulation signal having a pulse width determined depending on a reference voltage obtained by compensating the compensation voltage provided from the selector for the reference voltage from the reference voltage generator or 28 for generating a second reference voltage depending on the rate of the output voltage provided from the selector to generate a pulse width modulation signal having a pulse width determined depending on the second reference voltage, thereby controlling switching of the semiconductor switch in the power cell. 7. The H-bridge inverter for an alternating current as claimed in claim 5, wherein a media of the network is an optic fiber cable. 8. The H-bridge inverter for an alternating current as claimed in claim 5, wherein the network uses a CAN communication of a serial communication to reduce a communication line between the master controller and the cell controllers. Dated this 30th day of October 2006. OF D. P. AHUJA & CO. APPLICANTS' AGENT To The Controller of Patents, The Patent Office, Calcutta An H-bridge inverter for an alternating current motor is disclosed, in which output voltages of power cells can be output by allowing cell controllers to compensate input voltages of the power cells even in case that the input voltages are varied. A user can select an operation mode of each cell controller as a compensation mode for the input voltage and an output voltage control mode according to simple command frequency. Since the cell controller has a compensation control function for variation of the input voltage, it is possible to reduce communication load between a master controller and the cell controller.

Full Text

H-BRIDGE INVERTER FOR ALTERNATING CURRENT MOTOR BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to driving control of an alternating current motor which is used as a driving power source of an industrial high power equipment such as a pump, a fan, a compressor, a mixer, and a conveyer and requires a power source of a high voltage.
Specifically, the present invention relates to a high voltage inverter having an output voltage of 2 kilo volt (KV) to 5KV, and more particularly, to a high voltage inverter that can obtain a high output voltage by connecting a plurality of low voltage inverters (for example, inverters having an output voltage of 200V or 400V) in series per phase of three phases.
More specifically, the present invention relates to an inverter system that can be distributive controlled by cell controllers and a master controller, wherein the cell controllers are for individual control per power cell and the master controller is for controlling the cell controllers.
More specifically, the present invention relates to a high voltage inverter system in which an output voltage is not affected by variation of an input voltage of each power cell.
More specifically, the present invention relates to a high voltage inverter system in which cell controllers can prevent an output voltage from being affected by variation of an input voltage of each power cell without depending on a master controller.
1A
More specifically, the present invention relates to a high voltage inverter system that uses serial communication for communication between a master controller and a plurality of cell controllers and more specifically uses a controller area network (CAN) communication.
2. Description of the Background Art
An H-bridge inverter system which is a kind of a high voltage inverter system comprises an individual power source per power cell to supply a direct current power source to each power cell.
A transformer is used for individual power supply. A rectifier and a capacitor are used to convert an alternating current supplied from the transformer into a direct current and thus supply the direct current to a semiconductor switch in the power cell. A voltage rectified by the rectifier and smoothed by the capacitor is detected from both ends of the capacitor and at the same time is an input voltage of the power cell. This voltage is so called as a DC-link voltage in the related art.
However, the DC-link voltage per power cell may be varied due to voltage variation of an input alternating current power source of the transformer, i.e., a commercial alternating current power source. This does not allow an inverter to output an output voltage requested from an alternating current motor.
Furthermore, several DC-link voltages for power cell may be different from other DC-link voltages for power cell due to percent impedance voltage drop of the transformer, i.e., a secondary output voltage error of the transformer or the difference in individual capacitance of the capacitor. For this reason, unbalance may occur between output voltages of the inverter per phase. This causes an over
2
voltage to a semiconductor switch of a specific phase during regeneration, whereby the corresponding semiconductor switch may be burned.
To solve the above problem, the power cell may be connected to a circuit breaker so that the circuit breaker may be tripped when the over voltage occurs so as to protect the power cell.
However, problems occur in that if the circuit breaker connected to the power cell of one phase is tripped, voltages applied to the power cells of other phases increase and the operation of a load device such as motor may stop as the operation of the inverter stops.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide an H-bridge inverter for an alternating current motor, in which output voltages of power cells and a final output voltage of the inverter are not affected even by lump variation or individual variation of DC-link voltages for a plurality of power cells.
Another object of the present invention is to provide an H-bridge inverter for an alternating current motor, in which a plurality of cell controllers not a master controller can control respective power cells so as not affect output voltages of the power cells, thereby reducing computation load and communication load of the mater controller.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided an H-bridge inverter for an alternating current motor, which comprises a plurality of power cells connected in series per three phases, each having a semiconductor switch, a rectifying circuit and a smoothing condenser, the
3
semiconductor switch capable of switching controlled, and the rectifying circuit and the smoothing condenser for supplying a DC-link voltage to the semiconductor switch as an input voltage; a phase shift transformer having a primary winding and a plurality of secondary windings, the secondary windings being connected to each of the power cells to supply an individual three-phase alternating current power source; a master controller providing an output frequency command signal depending on a predetermined speed command, the output frequency command signal representing an output frequency of the inverter; a plurality of cell controllers communicatively connected to the master controller and each provided correspondingly to each of the power cell, for determining an input voltage to output voltage rate of each power cell as a rate of a command frequency according to the output frequency command signal from the master controller in comparison with a predetermined rated frequency of the alternating current motor, for generating a reference voltage depending on the rated voltage of the alternating current motor, for computing a compensation voltage according to the input voltage to output voltage rate with respect to the difference between the reference voltage and the detected DC-link voltage, for compensating the computed compensation voltage for the reference voltage, and for generating a pulse width modulation signal having a pulse width determined depending on the compensated reference voltage to control switching of the semiconductor switch in the power cell; and a network connected between the master controller and the cell controllers, for providing a communication path between the master controller and the cell controllers.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed
4
description of the present invention when taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.
In the drawings:
Figure 1 is a block diagram illustrating the whole configuration of an H-bridge inverter for an alternating current motor according to the present invention;
Figure 2 illustrates is a block diagram illustrating communication between a mater controller and cell controllers in an H-bridge inverter for an alternating current according to the present invention;
Figure 3 is a block diagram illustrating the detailed configuration of a cell controller of an H-bridge inverter for an alternating current motor according to one embodiment of the present invention;
Figure 4 is a block diagram illustrating the detailed configuration of a cell controller an H-bridge inverter for an alternating current motor according to another embodiment of the present invention;
Figure 5 is a waveform illustrating a method for modulating a pulse width of a pulse width modulation signal generator included in a cell controller of an H-bridge inverter for an alternating current motor according to the present invention;
Figure 6 is a flow chart illustrating the operation of a cell controller of an H-bridge inverter for an alternating current motor according to one embodiment of
5
the present invention; and
Figure 7 is a flow chart illustrating the operation of a cell controller of an H-bridge inverter for an alternating current motor according to another embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.
Figure 1 is a block diagram illustrating the whole configuration of an H-bridge inverter for an alternating current motor according to the present invention.
As shown in Figure 1, the H-bridge inverter for an alternating current motor according to the present invention comprises a phase shift transformer 71.
The phase shift transformer 71 comprises a primary winding 71A and a plurality of secondary windings 71B1-71Bn. The primary winding 71A is formed of a three-phase delta winding which receives a three-phase AC power source, for example AC 220V and a frequency of 60Hz. The secondary windings 71B1~71Bn transform the voltage, for example, AC 220V of the primary winding 71A into 24V and provide the 24V to each of power cells U1~Un, V1~Vn, W1~Wn and are formed of delta windings. TAB is a center tap provided between the primary winding 71A and the secondary windings 71B1~71Bn.
U-phase power cells U1~Un, V-phase power cells V1-Vn and W-phase power cells W1~Wn are connected in series per phase so that the sum of output voltages of the power cells connected in series per phase is provided to an alternating current motor 73 as each output voltage of corresponding phases U, V
6
and W. As described above, the alternating current motor 73 is used as a driving power source of an industrial high power equipment such as a pump, a fan, a compressor, a mixer, and a conveyer, and requires a power source of a high voltage of 2KV to 5KV.
As shown in a dotted line block of Figure 1 illustrating an enlarged inner configuration of the W-phase nth power cell Wn as an example of the power cells U1~Un, V1~Vn, W1~Wn, each of the power cells U1~Un, V1~Vn, W1~Wn according to the present invention comprises a rectifying circuit CON and a capacitor C, wherein the rectifying circuit CON rectifies any one of three-phase alternating currents among the secondary windings 71B1~71Bn to a direct current, and the capacitor C smoothes the direct current rectified by the rectifying circuit CON and provides the smoothed direct current to a semiconductor switch SW. A voltage across the capacitor C is an input voltage provided to the power cells U1~Un, V1~Vn, W1~Wn, in more detail an input voltage provided to the semiconductor switch SW in the power cells U1~Un, V1~Vn, W1~Wn. Hereinafter, the voltage will be referred to as a DC-link voltage.
For example, the semiconductor switch SW means for example an insulated gate bipolar transistor (IGBT) or a silicon control rectifier (SCR) that can . be turned on or off by a gate driving signal, i.e., an output signal of a pulse width modulation signal generator in the inverter of the present invention.
Each of the power cells U1~Un, V1~Vn, W1~Wn is a low voltage inverter for driving the alternating current motor 73 by inverting the input voltage, i.e., the DC-link voltage of the capacitor C to an alternating current voltage.
To control each of the power cells U1-Un, V1~Vn, W1~Wn, the number of cell controllers U1CC1~UnCCn, V1CC1~VnCCn, W1CC1~WnCCn corresponds
7
to the number of the power cells U1~Un, V1~Vn, W1~Wn, and the cell controllers are respectively connected to the power cells U1~Un, V1~Vn, W1~Wn.
The mater controller 72 controls all the cell controllers U1CC1~UnCCn, V1CC1~VnCCn, W1CC1~WnCCn, and provides an output frequency command signal in accordance with a predetermined speed command, wherein the output frequency command signal represents an output frequency of the inverter, i.e., the power cells U1~Un, V1~Vn, W1~Wn. The predetermined speed command means speed command data stored in a program memory means such as a read only memory (ROM) set on a program input by a program input means such as a program loader, which can be connected to the master controller 72 by a data transmission line.
The master controller 72 may have control functions such as restarting after instantaneous power failure, motor speed search, emergency stop, automatic energy saving, self diagnosis, and automatic tuning. However, since such control functions of the master controller 72 have nothing to do with the present invention, their detailed description will be omitted.
The master controller 72 is connected with the cell controllers U1CC1~UnCCn, V1CC1~VnCCn, W1CC1~WnCCn through a communication network N to enable mutual communication. The data transmitted from the master controller 72 to the cell controllers U1CC1~UnCCn, V1CC1~VnCCn, W1CC1~WnCCn may include information such as an output voltage command, a synchronizing signal, motor overheating, transformer overheating, fan error, and output phase deficiency. The data transmitted from the cell controllers U1CC1~UnCCn, V1CC1~VnCCn, W1CC1~WnCCn to the master controller 72 may include information such as over voltage, shortage voltage, over current, arm
8
short of the semiconductor switch, earth leakage, phase deficiency of the power cell. Since such data have nothing to do with the present invention, their detailed description will be omitted.
As shown in Figure 2, communication between the master controller 72 and the cell controllers U1CC1~UnCCn, V1CC1~VnCCn, W1CC1~WnCCn is realized by the communication network N. Preferably, an example of the communication network N comprises an optic fiber cable having fast data transmission speed and good insulation property to noise.
Furthermore, communication networking between the master controller 72 and the cell controllers U1CC1~UnCCn, V1CC1~VnCCn, W1CC1~WnCCn uses a Controller Area Network (CAN) having excellent characteristics in view of fast data transmission and insulation to noise.
Referring to Figure 2, blocks of the CAN shown in the master controller 72 represent the configuration that enables CAN communication in the master controller 72. Also, in Figure 2, the communication network N extended to the master controller 72 is comprised of an optic connector coated with an insulating material on an optic fiber. In addition to the above configuration, CAN drivers may separately be connected to the outside of the master controller 72 and the cell controllers U1CC1~UnCCn, V1CC1~VnCCn, W1CC1~WnCCn to enable communication between the CAN drivers through the communication network N.
Meanwhile, a block diagram illustrating the detailed configuration of a cell controller of an H-bridge inverter for an alternating current motor according to one embodiment of the present invention will be described with reference to Figure 3.
Since the cell controllers according to the present invention have the same configuration as one another, the first cell controller U1CC1 of the U-phase
9
cell controllers U1CC1~UnCCn connected in series will be described in detail with reference to Figure 3.
The cell controller U1CC1 determines an output voltage to the input voltage rate of the power cell U1 (see Figure 1) as a command frequency rate according to the output frequency command signal from the master controller 72 (see Figure 1) in comparison with a predetermined rated frequency of the alternating current motor 73. In other words, if the rated frequency of the alternating current motor is 60Hz and the command frequency according to the output frequency command signal is 30Hz, the cell controller U1CC1 determines the output voltage to the input voltage rate as 50%.
The cell controller U1CC1 generates a reference voltage depending on a rated voltage of the alternating current motor 73. For example, if the rated voltage of the alternating current motor is 200V, the cell controller U1CC1 computes 20V corresponding to 10% of 200V as a reference voltage value and stores the resultant value therein. In this case, the rate of 10% is predetermined and stored.
The cell controller U1CC1 computes a compensation voltage according to the output voltage to the input voltage rate with respect to the difference between the reference voltage and the detected DC-link voltage and compensates the computed compensation voltage with respect to the reference voltage. For example, since the reference voltage is 20V if the detected DC-link voltage is 18V, the difference voltage is 18V-20V=-2V and the compensation voltage is -1V obtained by multiplying the input voltage to output voltage rate corresponding to 50% by the difference voltage of -2V. The cell controller U1CC1 determines 19V obtained by adding -1V to the reference voltage of 20V as a new reference voltage in which input voltage variation is compensated. In other words, the
10
reference voltage decreases if the input voltage of the power cell, i.e., the DC-link voltage decreases, and vice versa. Although described later, increase of the reference voltage decreases a pulse width of a pulse width modulation signal for driving the semiconductor switch SW of the power cell, so as to decrease the turn-on time of the semiconductor switch, whereby the voltage supplied from the power cell to the alternating current motor decreases. On the other hand, decrease of the reference voltage increases the pulse width of the pulse width modulation signal for driving the semiconductor switch SW of the power cell, so as to increase the turn-on time of the semiconductor switch, whereby the voltage supplied from the power cell to the alternating current motor increases.
Furthermore, the cell controller U1CC1 generates the pulse width modulation signal having a pulse width determined depending on the compensated reference voltage to control switching of the semiconductor switch SW in the power cell U1. In other words, the cell controller U1CC1 determines the turn-on time of the semiconductor switch SW in the power cell U1 using a pulse width of a pulse signal supplied to a gate of the semiconductor switch SW. The pulse width, as shown in Figure 5, is determined by a time period between two dotted lines, i.e., for a time period of a triangle carrier wave having a peak value of 200V greater than or equal to a reference voltage of 100V. An output signal having a rectangular output waveform of high level is output from the cell controller U1CC1 to the gate of the semiconductor switch SW in the power cell U1 for the time period. Unlike an example shown in Figure 5, the peak value of the triangle carrier wave may be 20V if the compensated reference voltage is 19V. The voltage of the reference voltage is previously computed as a voltage value having a rate predetermined depending on the rated voltage value of the
11
alternating current motor connected to the inverter and at the same time is a normal DC-link voltage, i.e., a value predetermined by a normal charge voltage of the capacitor C of Figure 1. Accordingly, there is no change in the reference voltage value unless the capacitor C is replaced with another one having different capacity and the rated voltage value of the alternating current motor is varied. Also, the peak voltage of the triangle carrier wave is predetermined as a voltage as much as the predetermined value greater than the reference voltage, and a triangle carrier wave generating circuit generating a triangle carrier wave signal having a corresponding peak voltage is previously selected. Accordingly, there is no change in the peak voltage of the triangle carrier wave unless the triangle carrier wave generating circuit is replaced with another one.
In Figure 5, the peak voltage of the triangle carrier wave and the reference voltage are exemplarily suggested at 200V and 100V, respectively, not 20V and 19V, for convenience of description. Accordingly, it does not matter what the voltage values are.
The output signal having a rectangular output waveform of high level can be output from the cell controller U1CC1 to the gate of the semiconductor switch SW in the power cell U1 for a time period of the triangle carrier wave greater than or equal to the reference voltage of 19V
The detailed configuration of the cell controller U1CC1 according to Figure 3 and the operation of the cell controller U1CC1 will be described below.
The cell controller U1CC1 comprises an output voltage rate computing unit 81. The output voltage rate computing unit 81 computes the command frequency rate according to the output frequency command signal from the master controller 72, for example, a rate of 30Hz corresponding to 50% of the
12
predetermined rated frequency, for example, 60Hz of the alternating current motor 73, and determines the rate of the output voltage of the power cell U1 with respect to the DC-link voltage as the computed rate, i.e., 50%.
The cell controller U1CC1 comprises a reference voltage generator 82. The reference voltage generator 82 generates a reference voltage depending on the predetermined rated voltage of the alternating current motor. Supposing that the user previously inputs the rated voltage of 200V, the reference voltage generator 82 computes 20V corresponding to 10% of 200V and stores the computed value therein. In this case, the rate of 10% is predetermined by a manufacturer of the inverter and previously stored on a program by an input means such as a program loader
The cell controller U1CC1 comprises a difference voltage computing unit 83. The difference voltage computing unit 83 computes a difference voltage between the detected DC-link voltage and the reference voltage provided from the reference voltage generator. For example, since the reference voltage is 20V if the detected DC-link voltage is 18V, the difference voltage is 18V-20V=-2V. The difference voltage computing unit 83 provides the difference voltage -2V as the resultant value.
The cell controller U1CC 1 comprises a compensation voltage computing unit 84. The compensation voltage computing unit 84 obtains a compensation voltage of -1V by multiplying the rate, i.e., 50%, of the output voltage of the power cell to the DC-link voltage provided from the output voltage rate computing unit 81 by the difference voltage of -2V provided form the difference voltage computing unit 83.
The cell controller U1CC1 comprises a pulse width modulation signal
13
generator 86. To control switching of the semiconductor switch SW in the power cell U1, the pulse width modulation signal generator 86 generates a pulse width modulation signal having a pulse width determined depending on a voltage of 19V obtained by compensating the compensation voltage of -1V for the reference voltage of 20V from the reference voltage generator 82.
In more detail, the pulse width modulation signal generator 86 determines the turn-on time of the semiconductor switch SW in the power cell U1 using the pulse width of the pulse signal supplied to the gate of the semiconductor switch SW. The pulse width, as shown in Figure 5, is determined by a time period between two dotted lines, i.e., for a time period of a triangle carrier wave having a peak value of 200V greater than or equal to a reference voltage of 100V. An output signal having a rectangular output waveform of high level is output from the cell controller U1CC1 to the gate of the semiconductor switch SW in the power cell U1 for the time period. Unlike the example shown in Figure 5, the peak value of the triangle carrier wave may be 20V if the compensated reference voltage is 19V The output signal having a rectangular output waveform of high level can be output from the cell controller U1CC1 to the gate of the semiconductor switch SW in the power cell U1 for the time period of the triangle carrier wave greater than or equal to the reference voltage of 19V.
Accordingly, the power cell U1 is turned on for the high level time period of the pulse width modulation signal from the pulse width modulation signal generator 86." Thus, the power cell U1 inverts the DC-link voltage to the alternating current voltage so as to supply the alternating current voltage to the alternating current motor 73.
The operation of the cell controller of the H-bridge inverter for the
14
alternating current motor according to one embodiment of the present invention will be described briefly with reference to Figure 6.
Figure 6 is a flow chart illustrating the operation of the cell controller of the H-bridge inverter for the alternating current motor according to one embodiment of the present invention.
In step 1, the output voltage rate computing unit 81 of the cell controller U1CC1 computes the rate of command frequency, for example 30Hz according to the output frequency command signal from the master controller 72 to the predetermined rated frequency, for example 60Hz of the alternating current motor 73, that is 50%, and determines the rate of the output voltage of the power cell U1 to the DC-link voltage as the computed rate, i.e., 50%.
In step 2, the difference voltage computing unit 83 of the cell controller U1CC1 computes the difference voltage between the detected DC-link voltage and the reference voltage provided from the reference voltage generator 82. For example, since the reference voltage is 20V if the detected DC-link voltage is 18V, the difference voltage is 18V-20V=-2V. The difference voltage computing unit 83 provides the difference voltage -2V as the resultant value.
Afterwards, in step 3, the compensation voltage computing unit 84 of the cell controller U1CC1 obtains the compensation voltage of -1V by multiplying the rate, i.e., 50%, of the output voltage of the power cell to the DC-link voltage by the difference voltage of -2V provided from the difference voltage computing unit 83.
In step 4, the pulse width modulation signal generator 86 of the cell controller U1CC1 generates a new reference voltage, i.e., the compensated reference voltage of 19V by adding the compensation voltage of -1V provided form the compensation voltage computing unit 84 to the reference voltage of 20V
15
provided from the reference voltage generator 82.
Next, in step 5, the pulse width modulation signal generator 86 of the cell controller U1CC1 generates the pulse width modulation signal outputting the rectangular wave of high level for the time period of the triangle carrier wave greater than or equal to the new reference voltage by comparing the triangle carrier wave having a peak voltage of 20V with the new reference voltage, and provides the pulse width modulation signal to the gate of the semiconductor switch SW of the power cell U1 as a driving signal. Accordingly, the power cell U1 outputs a constant alternating current output voltage to the alternating current motor even if the input voltage of the power cell U1, i.e., the DC-link voltage is varied.
Meanwhile, the operation of the cell controller of the H-bridge inverter for the alternating current motor according to another embodiment of the present invention will be described with reference to Figure 4.
Since the cell controllers according to another embodiment of the present invention have the same configuration as one another, the first cell controller U1CC1 of the U-phase cell controllers U1CC1~UnCCn connected in series will be described in detail with reference to Figure 4.
The cell controller U1CC1 of the H-bridge inverter for the alternating current motor according to another embodiment of the present invention is different from that according to one embodiment of the present invention in that the operation of the cell controller depends on user's selection information. Accordingly, the cell controller U1CC1 of the inverter according to another embodiment of the present invention will be described on the basis of the difference from that according to the one embodiment of the present invention to
16
avoid repeated description.
The cell controller U1CC1 selectively executes any one of two control operations, which will be described below, depending on the user's selection information, i.e., selection information of an input voltage variation compensation mode or an output voltage command mode according to simple frequency command, more specifically user's selection information input during initial value setting of the inverter.
First, when the user inputs the value of the rated voltage of the alternating current motor connected with the inverter during initial value setting of the inverter and at the same time the user's selection is in an input voltage variation compensation mode, the cell controller U1CC1 computes the compensation voltage according to the output voltage to the input voltage rate with respect to the difference between the reference voltage and the DC-link voltage and compensates the computed compensation voltage for the reference voltage.
To control switching of the semiconductor switch in the power cell U1, the pulse width modulation signal generator generates the pulse width modulation signal having a pulse width determined depending on the compensated reference voltage.
Second, when the user fails to input the value of the rated voltage of the alternating current motor connected with the inverter during initial value setting of the inverter or the user's selection is in an output voltage command mode according to simple frequency command, the cell controller U1CC1 determines the input voltage to output voltage rate of the power cell U1 as a rate of the command frequency according to the output frequency command signal from the master controller in comparison with the predetermined rated frequency of the
17
alternating current motor, and generates a second reference voltage different from the first reference voltage depending on the determined rate and a pulse width modulation signal having a pulse width determined depending on the second reference voltage.
Meanwhile, the detailed configuration and operation of the cell controller according to another embodiment of the present invention will be described with reference to Figure 4.
The detailed configuration and operation of the cell controller according to another embodiment of the present invention will be described on the basis of the difference from those according to the one embodiment of the present invention to avoid repeated description.
The cell controller according to another embodiment of the present invention additionally comprises a selector 85 that provides an output voltage rate of the output voltage rate computing unit or the compensation voltage provided from the compensation voltage computing unit depending on a predetermined selection mode of the user.
A contact point 85a inside the selector 85 is connected to the output voltage rate output from the output voltage rate computing unit depending on the predetermined selection mode, and another contact point 85b inside the selector 85 is connected to the compensation voltage output from the compensation voltage computing unit depending on the predetermined selection mode.
Preferably, the switch and the contact points of the selector 85 shown in Figure 4 can be realized by selection data stored in the cell controller U1CC1 and a process program according to the selection data.
The pulse width modulation signal generator 86 included in the cell
18
controller according to another embodiment of the present invention may generate the pulse width modulation signal having the pulse width determined depending on the new reference voltage obtained by compensating the compensation voltage from the compensation voltage computing unit 84 for the first reference voltage from the reference voltage generator 82 depending on the output from the selector 85. Also, the pulse width modulation signal generator 86 may generate the second reference voltage depending on the output voltage rate provided form the selector 85 and also generate the pulse width modulation signal having the pulse width determined depending on the second reference voltage. The second reference voltage is obtained by multiplying the output voltage rate by another reference voltage not the first reference voltage provided from the reference voltage generator 82, wherein the another reference voltage is the detected input voltage, i.e., the DC-link voltage and may be varied due to voltage variation of a commercial alternating current power source, the difference in capacity of the capacitor C, or the difference between secondary voltages per power cell of the phase shift transformer.
Meanwhile, the operation of the cell controller of the H-bridge inverter for the alternating current motor according to another embodiment of the present invention will be described briefly with reference to Figure 7.
Figure 7 is a flow chart illustrating the operation of the cell controller of the H-bridge inverter for the alternating current motor according to another embodiment of the present invention.
The operation of the cell controller of the H-bridge inverter according to another embodiment of the present invention will be described with reference to the flow chart of Figure 7 and Figure 4.
19
First, the cell controller U1CC1 of the H-bridge inverter according to another embodiment of the present invention checks whether the rated voltage of the alternating current motor to be controlled by the inverter is set, i.e., whether data of the rated voltage input by the user are stored in step 10. If the rated voltage of the alternating current motor is set in step 10, the cell controller U1CC1 reads the set rated voltage value from a data memory means (not shown) such as a memory and advances to step 11.
If the rated voltage of the alternating current motor is not set in step 10, the cell controller U1CC1 advances to step 12.
In step 11, the cell controller U1CC1 checks, using the selector 85, whether the user's selection for the operation mode of the cell controller U1CC1 is in the input voltage variation compensation mode or the output voltage command mode according to the simple frequency command.
If the operation mode of the cell controller U1CC1 has been selected in the input voltage variation compensation mode in step 11, the cell controller U1CC1 advances to step 14. Otherwise, if the operation mode of the cell controller U1CC1 has been selected in the output voltage command mode according to the simple frequency command, the cell controller U1CC1 advances to step 12.
If the cell controller U1CC1 advances to step 14, the output voltage rate computing unit 81 of the cell controller U1CC1 computes the rate of the command frequency according to the output frequency command signal from the master controller in comparison with the predetermined rated frequency of the alternating current motor and determines the rate of the output voltage of the power cell to the DC-link voltage as the resultant rate.
20
Afterwards, the cell controller U1CC1 advances to step 15 so that the difference voltage computing unit 83 of the cell controller U1CC1 computes the difference voltage between the detected DC-link voltage and the reference voltage according to the rated voltage provided from the reference voltage generator 82.
Then, the cell controller U1CC1 advances to step 16 so that the compensation voltage computing unit 84 of the cell controller U1CC1 obtains the compensation voltage by multiplying the output voltage rate of the power cell to the DC-link voltage provided from the output voltage rate computing unit 81 by the difference voltage provided from the difference voltage computing unit 83.
Next, the cell controller U1CC1 advances to step 17 so that the pulse width modulation signal generator 86 of the cell controller U1CC1 generates the new reference voltage, i.e., the compensated reference voltage by adding the compensation voltage provided from the compensation voltage computing unit 84 to the reference voltage provided from the reference voltage generator 82.
Next, the cell controller U1CC1 advances to step 17 so that the pulse width modulation signal generator 86 of the cell controller U1CC1 generates the pulse width modulation signal outputting the rectangular wave of high level for the time period of the triangle carrier wave greater than or equal to the new reference voltage by comparing the triangle carrier wave shown in Figure 5 with the new reference voltage.
Afterwards, although not shown in Figure 7, the gate of the semiconductor switch in the power cell is driven for the high level time period of the pulse width modulation signal so as to turn on the semiconductor switch, whereby the DC-link voltage from the capacitor C is inverted to the alternating current and the sum of
21
the output voltages of the power cells connected in series per phase is supplied to the alternating current motor.
Meanwhile, if the cell controller U1CC1 advances to step 12, the pulse width modulation signal generator 86 of the cell controller U1CC1 generates the second reference voltage depending on the output voltage rate provided from the selector 85. In this case, the second reference voltage is the detected input voltage, i.e., the DC-link voltage and may be varied due to voltage variation of the commercial alternating current power source, the difference in capacity of the capacitor C, or the difference between secondary voltages per power cell of the phase shift transformer. Also, if the DC-link voltage is less or greater than a desirable voltage level, a boost voltage of positive (+) or negative (-) set by the user may be added to the second reference voltage to generate a new second reference voltage.
Afterwards, the cell controller U1CC1 advances to step 13 so that the pulse width modulation signal generator 86 of the cell controller U1CC1 generates the pulse width modulation signal having the pulse width determined depending on the newly generated second reference voltage and provides the generated pulse width modulation signal as a gate driving signal of the semiconductor switch of the corresponding power cell U1.
As described above, the advantages of the present invention are as follows.
According to the H-bridge inverter for an alternating current motor, the output voltages of the power cells and the final output voltage of the inverter are not affected even by lump variation or individual variation of the DC-link voltages for the power cells.
22
Also, according to the H-bridge inverter for an alternating current motor, the user can select the operation mode of the cell controller in the input voltage variation compensation mode or the output voltage command mode according to the simple frequency command.
Finally, according to the H-bridge inverter for an alternating current motor, the plurality of cell controllers not a single master controller can control respective power cells so as not affect output voltages of the power cells, thereby reducing computation load and communication load of the mater controller.
As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims.
23
What is claimed is:
1. An H-bridge inverter for an alternating current motor, comprising:
a plurality of power cells connected in series per three phases, each having a semiconductor switch, a rectifying circuit and a smoothing condenser, the semiconductor switch capable of switching controlled, and the rectifying circuit and the smoothing condenser for supplying a DC-link voltage to the semiconductor switch as an input voltage;
a phase shift transformer having a primary winding and a plurality of secondary windings, the secondary windings being connected to each of the power cells for supplying an individual three-phase alternating current power source;
a master controller for providing an output frequency command signal depending on a predetermined speed command, the output frequency command signal representing an output frequency of the inverter;
a plurality of cell controllers provided correspondingly with each of said power cell and connected communicatively to the master controller for determining an input voltage to output voltage rate of each power cell as a rate of a command frequency according to the output frequency command signal from the master controller in comparison with a predetermined rated frequency of the alternating current motor, for generating a reference voltage depending on the rated voltage of the alternating current motor, for computing a compensation voltage according to the input voltage to output voltage rate with respect to the difference between the reference voltage and the detected DC-link voltage, for compensating the computed compensation voltage for the reference voltage, and for generating a pulse width modulation signal having a pulse width determined
24
depending on the compensated reference voltage to control switching of the semiconductor switch in the power cell ; and
a network connected between the master controller and the cell controllers, for providing a communication path between the master controller and the cell controllers.
2, The H-bridge inverter for an alternating current as claimed in claim 1, wherein the cell controller comprises:
an output voltage rate computing unit for computing a rate of the command frequency according to the output frequency command signal from the master controller in comparison with the predetermined rated frequency of the alternating current motor and for determining a rate of the output voltage of the power cell to the DC-link voltage using the computed rate;
a reference voltage generator for generating a reference voltage depending on a predetermined rated voltage of the alternating current motor;
a difference voltage computing unit for computing a difference voltage between the detected DC-link voltage and the reference voltage provided from the reference voltage generator;
a compensation voltage computing unit for obtaining a compensation voltage by multiplying the rate of the output voltage of the power cell to the DC-link voltage provided form the output voltage rate computing unit by the difference voltage provided from the difference voltage computing unit; and
a pulse width modulation signal generator for generating a pulse width modulation signal having a pulse width determined depending on a reference voltage obtained by compensating the compensation voltage from the
25
compensation voltage computing unit for the reference voltage from the reference voltage generator, thereby for controlling switching of the semiconductor switch in the power cell.
3. The H-bridge inverter for an alternating current as claimed in claim 1,
wherein the network is comprised of an optic fiber cable.
4. The H-bridge inverter for an alternating current as claimed in claim 1,
wherein communication between the master controller and the cell controllers
through the network is carried out by a Controller Area Network (CAN)
communication.
5. An H-bridge inverter for an alternating current, comprising:
a plurality of power cells connected in series per three phases, each having a semiconductor switch, a rectifying circuit and a smoothing condenser, the semiconductor switch capable of switching controlled, and the rectifying circuit and the smoothing condenser for supplying a DC-link voltage to the semiconductor switch as an input voltage;
a phase shift transformer having a primary winding and a plurality of secondary windings, the secondary windings being connected to each of the power cells for supplying an individual three-phase alternating current power source;
a master controller for providing an output frequency command signal depending on a predetermined speed command, the output frequency command signal representing an output frequency of the inverter;
26
a plurality of cell controllers provided correspondingly with said power cell and connected with the master controller communicatively for determining an input voltage to output voltage rate of the power cell as a rate of a command frequency according to the output frequency command signal from the master controller in comparison with a predetermined rated frequency of the alternating current motor, for generating a first reference voltage depending on the rated voltage of the alternating current motor if an input voltage variation compensation mode is previously selected by a user, for computing a compensation voltage according to the input voltage to output voltage rate with respect to the difference between the first reference voltage and the detected DC-link voltage, for compensating the computed compensation voltage for the first reference voltage, for generating a pulse width modulation signal having a pulse width determined depending on the compensated first reference voltage or, if an output voltage command mode according to simple frequency command is previously selected by the user, for determining the input voltage to output voltage rate of the power cell as the rate of the command frequency according to the output frequency command signal from the master controller in comparison with the predetermined rated frequency of the alternating current motor, for generating a second reference voltage depending on the determined rate and generating a pulse width modulation signal having a pulse width determined depending on the second reference voltage, thereby controlling switching of the semiconductor switch in the power cell; and
a network connected between the master controller and the cell controllers, for providing a communication path between the master controller and the cell controllers.
27
6. The H-bridge inverter for an alternating current as claimed in claim 5, wherein the cell controller comprises:
an output voltage rate computing unit for computing a rate of the command frequency according to the output frequency command signal from the master controller in comparison with the predetermined rated frequency of the alternating current motor and for determining a rate of the output voltage of the power cell to the DC-link voltage using the computed rate;
a reference voltage generator for generating a first reference voltage depending on a predetermined rated voltage of the alternating current motor;
a difference voltage computing unit for computing a difference voltage between the detected DC-link voltage and the first reference voltage provided from the reference voltage generator;
a compensation voltage computing unit for obtaining a compensation voltage by multiplying the rate of the output voltage of the power cell to the DC-link voltage provided form the output voltage rate computing unit by the difference voltage provided from the difference voltage computing unit;
a selector for providing the rate of the output voltage from the output voltage rate computing unit or the compensation voltage from the compensation voltage computing unit depending on a predetermined selection mode of the user; and
a pulse width modulation signal generator for generating either a pulse width modulation signal having a pulse width determined depending on a reference voltage obtained by compensating the compensation voltage provided from the selector for the reference voltage from the reference voltage generator or
28
for generating a second reference voltage depending on the rate of the output voltage provided from the selector to generate a pulse width modulation signal having a pulse width determined depending on the second reference voltage, thereby controlling switching of the semiconductor switch in the power cell.
7. The H-bridge inverter for an alternating current as claimed in claim 5,
wherein a media of the network is an optic fiber cable.
8. The H-bridge inverter for an alternating current as claimed in claim 5,
wherein the network uses a CAN communication of a serial communication to
reduce a communication line between the master controller and the cell
controllers.

Dated this 30th day of October 2006.
OF D. P. AHUJA & CO. APPLICANTS' AGENT
To
The Controller of Patents,
The Patent Office,
Calcutta
An H-bridge inverter for an alternating current motor is disclosed, in which output voltages of power cells can be output by allowing cell controllers to compensate input voltages of the power cells even in case that the input voltages are varied. A user can select an operation mode of each cell controller as a compensation mode for the input voltage and an output voltage control mode according to simple command frequency. Since the cell controller has a compensation control function for variation of the input voltage, it is possible to reduce communication load between a master controller and the cell controller.

Documents:

01147-kol-2006-abstract.pdf

01147-kol-2006-assignment.pdf

01147-kol-2006-claims.pdf

01147-kol-2006-correspondence others.pdf

01147-kol-2006-correspondence-1.1.pdf

01147-kol-2006-description(complete).pdf

01147-kol-2006-drawings.pdf

01147-kol-2006-form-1.pdf

01147-kol-2006-form-2.pdf

01147-kol-2006-form-3-1.1.pdf

01147-kol-2006-form-3.pdf

01147-kol-2006-general power of authority.pdf

1147-KOL-2006-(17-02-2014)-ABSTRACT.pdf

1147-KOL-2006-(17-02-2014)-ANNEXURE TO FORM 3.pdf

1147-KOL-2006-(17-02-2014)-CLAIMS.pdf

1147-KOL-2006-(17-02-2014)-CORRESPONDENCE.pdf

1147-KOL-2006-(17-02-2014)-DESCRIPTION.pdf

1147-KOL-2006-(17-02-2014)-FORM-13.pdf

1147-KOL-2006-(17-02-2014)-OTHERS.pdf

1147-KOL-2006-(17-02-2014)-PETITION UNDER RULE 137-1.pdf

1147-KOL-2006-(17-02-2014)-PETITION UNDER RULE 137.pdf

1147-kol-2006-form 18.pdf

abstract-01147-kol-2006.jpg

« Previous Patent

Next Patent »

Patent Number

265991

Indian Patent Application Number

1147/KOL/2006

PG Journal Number

13/2015

Publication Date

27-Mar-2015

Grant Date

26-Mar-2015

Date of Filing

30-Oct-2006

Name of Patentee

LS INDUSTRIAL SYSTEMS CO., LTD.

Applicant Address

84-11, 5Ga, NAMDAEMUN-RO JUNG-GU

Inventors:

#	Inventor's Name	Inventor's Address
1	JEON JAE-HYUN	43-4, DAPSIMNI 2-DONG DONGDAEMUN-GU

PCT International Classification Number

H02P21/00; H02P27/04;

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	NA	2006-10-30	Republic of Korea