Title of Invention	DOOR INTERLOCKING SYSTEM FOR AN ELECTRICAL SWITCHING APPARATUS
Abstract	A door interlocking system for an electrical switching apparatus 101 mounted on an enclosed housing, comprising a door lock 109 on the housing of the switching apparatus 101. A sensor assembly 106 is configured to determine the position of the switching apparatus based on markings 104 on the switching apparatus, where the markings 104 constitute various positions of the switching apparatus. A controller 108 is electrically connected to the sensor assembly 106 and configured to control the locking or unlocking of the door of the housing of the switching apparatus relating to the position of the switching apparatus. Such interlocking system prevents serious injury to maintenance personnel and damage to the electrical equipment. Also, it is adaptable to any switchboard and any switching apparatus.FIG. 3

Title of Invention

DOOR INTERLOCKING SYSTEM FOR AN ELECTRICAL SWITCHING APPARATUS

Abstract

A door interlocking system for an electrical switching apparatus 101 mounted on an enclosed housing, comprising a door lock 109 on the housing of the switching apparatus 101. A sensor assembly 106 is configured to determine the position of the switching apparatus based on markings 104 on the switching apparatus, where the markings 104 constitute various positions of the switching apparatus. A controller 108 is electrically connected to the sensor assembly 106 and configured to control the locking or unlocking of the door of the housing of the switching apparatus relating to the position of the switching apparatus. Such interlocking system prevents serious injury to maintenance personnel and damage to the electrical equipment. Also, it is adaptable to any switchboard and any switching apparatus.FIG. 3

Full Text	DOOR INTERLOCKING SYSTEM FOR AN ELECTRICAL SWITCHING APPARATUS FIELD OF THE INVENTION The present invention relates to the fields of electrical switching apparatus. The present invention specifically relates to a door interlocking system for controlling access to a circuit breaker housing. BACKGROUND OF THE INVENTION In general, electrical switching apparatus used in power distribution systems are mounted within a housing assembly either individually or in combination with other switchgears such as circuit breakers. Some electrical switching apparatus, particularly low voltage circuit breakers are quite large, (n order to facilitate movement during installation, removal and maintenance, the circuit breaker is commonly coupled to rollers/racking mechanism, which permit such circuit breaker to be drawn out of the housing assembly. This circuit breaker is commonly known as draw-out type circuit breaker/such apparatus. Referring to FIG. 1, a schematic view of various operations of a draw out type circuit breaker 1 is illustrated, in accordance with prior art. During operation, the draw out type circuit breaker 1 exhibits four positions, such as Working, Test, Isolated and Disconnected, in the switchboard. The circuit breaker 1 can be mounted on a mounting plate 5 assembled to the switchboard frame 4. In working position, the circuit breaker 1 is connected to the main power supply 2 as well as to the auxiliary supply, which ensures that the circuit breaker 1 is in normal working condition, as shown in FIG. 1a. In test position, the main power supply 2 is disconnected but auxiliary supply is still connected to the circuit breaker 1, as shown in FIG. lb. This position is used to test the functionality of the auxiliary circuit. Moreover, in isolated position, both the main power supply 2 and the auxiliary supply are disconnected from the circuit breaker 1, as shown in FIG. 1c. Clearance between the circuit breaker terminal and the busbar 3 is more than or equal to isolation distance, where servicing of the circuit breaker 1 is done in this position. Finally, in disconnected position, the circuit breaker 1 is disconnected both electrically and mechanically from the switchboard. In order to prevent injury, e.g. electrical shock, it is often desirable to limit access to the circuit breaker 1 within the housing. Such circuit breaker 1 must be drawn out of the housing to access and perform maintenance. Improper maintenance procedures, i.e. failure to turn OFF the circuit breaker 1, cause serious injury to maintenance personnel and damage to the electrical equipment during arc flashover while the door 6 being opened. Hence, while withdrawing the circuit breaker 1 from the switchboard, it is essential to retain the switchboard door 6, as shown in FIG. 2, in locked condition until the circuit breaker reaches the isolated position. In case of pushing in, the door should be locked, once the circuit breaker 1 crosses the isolated position. This type of interlocking system is mandatory to protect the operator from the electrical hazards. There are few electrical and mechanical interlocking systems available in the switchboards. But these types of interlocking systems are either device specific or switchboard specific. Further, the existing door locking system could be manually manipulated by maintenance personnel such that the door locking is rendered ineffective. Also the existing Mechanical Interlocks can be made inactive during certain circumstances by tying the locking lever by a string. Such procedures not only make the mechanical interlock useless but also obstruct the very safety feature of the mechanical interlock which is intended. FIG. 2 shows a schematic view of existing door interlocking systems, in accordance with prior art. Referring to FIG. 2a, a mechanical interlocking system utilizes a number of mechanical linkages. Also over a period of time the linkages may be subjected to lot of wear and tear and may not properly engage the door lock, thereby requiring some manual adjustments with the link mechanisms. Such mechanical interlocking system cannot be used for others equipments, since it is designed depending on the mechanism of a particular type of circuit breakers. Referring to FIG. 2b, an electrical interlocking system requires some additional wiring in the switchboard to operate an electrical door lock 7 and it is also breaker specific. With respect to the conventional door interlocking systems, it is very complicated and not adaptable to any circuit breakers or any switchboards. Moreover, the mechanical door interlock uses complex mechanisms, and consists of lots; of moving parts which become cumbersome during maintenance. Therefore, it is essential to design a simple and efficient door interlocking system to overcome the above-mentioned drawbacks. OBJECT OF THE INVENTION An object of the present invention is to provide a door interlocking system for controlling access to a circuit breaker housing, which prevents serious injury to maintenance personnel and damage to the electrical equipment. Another object of the present invention is to provide a door interlocking system for controlling access to a circuit breaker housing, which is adaptable to any switchboard and any circuit breaker. A further object of the present invention is to provide a door interlocking system for controlling access to a circuit breaker housing, which is easy to operate and involves less wear and tear due to very few mechanical moving parts. SUMMARY OF THE INVENTION According to one aspect, the present invention, which achieves this objective, relates to a door interlocking system for an electrical switching apparatus mounted on an enclosed housing, comprising a door lock on the housing of the switching apparatus. A sensor assembly is configured to determine the position of the switching apparatus based on markings on the switching apparatus, where the markings constitute various positions of the switching apparatus. A controller is electrically connected to the sensor assembly and configured to control the locking or unlocking of the door of the housing of the switching apparatus relating to the position of the switching apparatus. Such interlocking system prevents serious injury to maintenance personnel and damage to the electrical equipment. Also, it is adaptable to any switchboard and any switching apparatus. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be discussed in greater detail with reference to the accompanying Figures. FIG. 1 shows a schematic view of various operations of a draw out type circuit breaker, in accordance with prior art; FIG. 2 illustrates a schematic view of existing door interlocking systems, in accordance with prior art; FIG. 3 illustrates an isometric view depicting location of a sensor assembly of a door interlocking system, in accordance with an,exemplary embodiment of the present invention; FIG. 4: illustrates a schematic view of the door interlocking system with a circuit breaket" assembled on a mounting plate, in accordance with an exemplary embodiment of the present invention; FIG. 5 illustrates a schematic view showing working principle of an optical sensor, in accordance with an exemplary embodiment of the present invention; FIG. 6- illustrates a significance of cryptogram for an ultrasonic depth sensor, in accordance with an exemplary embodiment of the present invention; FIG. 7 illustrates a functional block diagram of the door interlocking system, in accordance with an exemplary embodiment of the present invention; FIG. 8 illustrates a flow chart showing the sequence of operation of the door interlocking system while drawing out the circuit breaker, in accordance with an exemplary embodiment of the present invention; and FIG. 9 illustrates a flow chart showing the sequence of operation of the door interlocking system while pushing in the circuit breaker, in accordance with an exemplary'embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 3, an isometric view depicting location of a sensor assembly 106 of a door interlocking system, in accordance with an exemplary embodiment of the present invention. A drawn out type circuit breaker 101 can be mounted on a mounting plate 102, which is connected to a switchboard frame 103. The door interlocking system can optically monitor the positional status of the drawn out type circuit breaker 101 with respect to working, test and isolated status. The system comprises a sensor assembly 106 placed at a strategic location along the guiding path of the withdrawable circuit breaker 101 to detect the position of the circuit breaker 101. In addition, the sensor assembly 106 includes a transmitter 106a and a receiver 106b placed in tandem arrangement on any side of the enclosure. Generally, the transmitter 106a consists of a light source (visible light beam or laser beam or infrared beam) and the receiver 106b consists of a photo diode or any other photovoltaic cells or optical sensor or camera, which are placed next to each other in a defined location. The light 105 emitted by the transmitter 106a is tuned to a specific frequency and the receiver 106b is designed to detect only the tuned frequency light corresponding to cryptogram markings 104 placed on the circuit breaker 101. FIG. 4 illustrates a schematic view of the door interlocking system with the circuit breaker 101 assembled on the mounting plate 102, in accordance with an exemplary embodiment of the present invention. For example, let us consider that the optical sensor 106 is utilized the door interlocking system. In order to sense the position of the circuit breaker 101, a cryptogram 104 is pasted on the side of the circuit breaker 101 in relation to the position of the optical transmitter 106a and the optical receiver 106b. The cryptogram 104 contains three black bars 104a, 104b and 104c, where each bar varies in width, but not in height, as shown in FIG. 5, which illustrates a schematic view showing working principle of the optical sensor 106, in accordance with an exemplary embodiment of the present invention. The preferred cryptograms 104 are placed sequentially on either side of the circuit breaker 101 in in-line form. Such cryptograms 104 have to be placed in a defined position with respect to the desired positions of the circuit breaker 101. Furthermore, the optical transmitter 106a, i.e. light source, transmits the light beam 105 falling on the black bars 104a, 104b and 104c of the cryptogram 104 to read the position of the circuit breaker 101. The positions of the black bars 104a, 104b and 104c with respect to the optical sensor 106 are calibrated in such a way that the transmitted light beam 105 falls on the black bar 104a if the circuit breaker 101 is in working position, on the black bar 104b if the breaker 101 is in test position ana on ine oiacK oar la m louiaicu (JWOIUM, as shown in FIGS. 4a, 4b and 4c, respectively. Then, the optical receiver 106b, i.e. photo diode, measures the intensity of the light reflected back from the respective black bars black bar 104a, 104b and 104c of the cryptogram 104 and generates a voltage waveform signal corresponding to the measured intensity of the reflected light, as shown in FIG. 5. The generated waveform signal can be used to measure the widths of the black bars 104a, 104b and 104c and spaces in the cryptogram 104, which defines the exact position (working, test or isolation position) of the circuit breaker 101, as clearly explained in FIG. 5. The dark black bars 104a, 104b and 104c in the cryptogram 104 absorb the light 105 whereas the white spaces reflect the light 105, so that the voltage waveform signal generated by the photo diode 106b is an exact replica of the bar and space pattern in the cryptogram 104. Moreover, the optical sensors are limited to specific environments like home, commercial buildings, etc, since it is not suitable for harsh environments with risk of blockage due to external materials, e.g. dust. Particularly, such optical sensor for position detection is not suitable if the switchboard is placed in a harsh environment and if the atmosphere contains lots of dust particles (fly ash, smoke and sawdust), which are very common in manufacturing industries. In such case, ultrasonic depth sensors can be used, since it exhibits high accuracy even in harsh environment. In case of ultrasonic depth sensor, the cryptogram 111 placed in the circuit breaker 101 can be modified to make it as ultrasonic wave sensitive. Such cryptogram 111 contains three blind rectangular cuts 111a, 111b and 111c of varying depth, namely A1, A2 and A3, as shown in FIG. 6, which illustrates a significance of cryptogram for the ultrasonic depth sensor, in accordance with an exemplary embodiment of the present invention. The ultrasonic wave falls on these rectangular cuts 111a, 111b and 111c and measures the depth. The position of the cuts 111a, 111b and 111c is calibrated such a way that ultrasonic wave falls on the depth A1, which concludes that the breaker 101 is in connected or working condition. Similarly, the depths A2 and A3 conclude that the breaker 101 is in test condition and isolated condition, respectively. Hence, the optical detection can be used for indoor installation for buildings, hospitals, hotels etc., whereas the ultrasonic detection is efficient for shop floor of manufacturing industries and power plant, which exhibits huge variation of temperature and harsh environment with lots of dust particles. Referring to FIG. 7, a functional block diagram of the door interlocking system is illustrated, in accordance with an exemplary embodiment of the present invention. The sensor assembly 106 reads the input from the cryptogram 104 placed on the circuit breaker 101, i.e. after reading the width or depth of the cryptogram. The sensor assembly 106 transmits an output signal to a controller 108, as shown in FIGS. 4 and 7, where the output signal is in the form of voltage waveform. The controller 108 decodes the voltage waveform signal in a manner similar to the way Morse code dots and dashes are decoded. The controller 108 also analyses the position of the breaker 101 and generates a command in relation to the analyzed breaker position. Further, the controller 108 is programmed to send the command to an electromagnetic lock 109 so as to allow opening/closing of the switchboard door depending upon the signal received from the optical sensor assembly 106. The electromagnetic door lock 109 is placed on the top of enclosure of the electrical switching apparatus for locking the front door of the switchboard or panel. The door lock 109 is energized into locked or unlocked states for closing or opening of the switchboard door, respectively. For the purpose of clear explanation, the discussion, examples and illustrations set forth in this specification deal with electromagnetic door lock, but as explained hereinabove, my novel system is not limited to such, but comprises other types of door lock. Moreover, the controller 108 initially traces the position of the circuit breaker 101 by measuring the width or depth of the cryptogram 104 and the output is displayed on an LCD display 110. The LCD display 110 displays the current position of the circuit breaker 101 to maintenance personnel. FIG. 8 illustrates a flow chart showing the sequence of operation of the door interlocking system while drawing out the circuit breaker, in accordance with an exemplary embodiment of the present invention. While drawing out the circuit breaker 101, the breaker 101 should be disconnected electrically and mechanically from the switchboard. In this phenomenon, initially the breaker 101 is in working condition and the door is in locked state. As illustrated in step 801, the sensor assembly 106 reads the position of the circuit breaker 101. In particular, the sensor 106 reads the bar 104a or cut 111a and the LCD 110 displays the breaker position as 'WORKING', as depicted in step 802. Similarly, when the breaker 101 is drawn to test condition, the sensor 106 read the bar 104b or cut 111b and the LCD 110 displays the position as TEST'. When the breaker 101 is drawn to isolated condition, the sensor 106 read the bar 104c or cut 111c and the LCD 110 displays the position as 'ISOLATED'. As shown in step 803, the controller 108 checks that the breaker 101 is reached the isolated position. If the breaker 101 is not reached the isolated position, the controller 108 sends the command to the electromagnetic lock 109 to retain it in locked condition and checks for the signal from the sensor 106, as illustrated in step 806. If the breaker 101 is reached the isolated position, the controller 108 sends a signal to the electromagnetic lock 109 to unlock the door and activates the mechanical stopper to ensure an additional safety, as shown in steps 804 and 805. Such mechanical stopper is triggered and activated by certain actuator, which allows the breaker to be pushed in from isolated position unless and until the door is in closed position. Thereafter, the breaker 101 can be completely removed from the switchboard. FIG. 9 illustrates a flow chart showing the sequence of operation of the door interlocking system while pushing in the circuit breaker, in accordance with an exemplary embodiment of the present invention. While pushing in the circuit breaker 101, the breaker 101 should be assembled back inside the switchboard. In this case, initially the door is in unlocked condition and the LCD 110 displays the position as 'ISOLATED'. As illustrated in step 901, the sensor assembly 106 reads the position of the circuit breaker 101. As shown in step 902, the LCD 110 displays the position of the breaker 101 as isolated or test or working. As shown in step 903, checking is made whether the breaker 101 is reached the isolated position. If the breaker 101 is not reached the isolated position, the controller 108 checks for the signal from the sensor 106, as illustrated in step 907. As illustrated in steps 904 and 905, once the circuit breaker 101 crosses the isolated position i.e. it is pushed further in, the controller 108 checks whether the door is locked and sends a signal to the electromagnetic lock 109 to keep the door in locked condition. Then, the circuit breaker 101 traverses to test position and the LCD 110 displays the position as 'TEST, the lock retains the door closed. Finally, the circuit breaker 101 reaches working condition and the LCD 110 displays the position as 'WORKING'. The circuit breaker 101 touches the Busbar of power supply 107 and gets ready to work. The controller 108 keeps the door in locked condition. As illustrated in step 906, the controller 108 deactivates the mechanical stopper to engaging the circuit breaker back into working condition if the door is in locked state. If the door is in unlocked state, the mechanical stopper not allows the breaker 101 to push in, as depicted in step 907. While drawing out the circuit breaker 101 from the connections, a stopping means 112, like mechanical stopper, is activated once the breaker 101 crosses a predetermined position. In the present embodiment, the predetermined position is defined as the test position. This stopping means 112 once activated restricts the movement of the circuit breaker 101 back to the working condition. In order to engage the circuit breaker 101 back to the working position, the stopping means 112 should be deactivated. This deactivation of the stopping means 112 is controlled by the controller 108. The controller 108 is configured such that, on meeting of certain criteria it deactivates the stopping means 112 and thus allowing the movement of the circuit breaker 101 back to the working condition. The controller 108 is configured to receive input from the electromagnetic lock 109 on the condition of locking. When the electromagnetic lock 109 is in the locked, the controller 108 deactivates the stopping means 112 and thus allows movement of circuit breaker 101. I The optical/ultrasonic sensor and the electromagnetic door lock are easily installed at any preferred location. This interlocking system is made to withdraw the current either directly from the incomer (using some step down transformer) or through a rechargeable battery placed exclusively for this purpose. The required amount of power to operate the electromagnetic door lock is 12 V/ 500 mA. One of the significant advantages of this interlocking system is that there are no moving parts involved unlike the conventional mechanical linkages, so thereby it is easy to operate and also involves less wear and tear. Moreover, such interiocking system is adaptable to any switchboard and any circuit breaker. In case of emergency, an optional electrical switch can be provided to deactivate the electromagnetic lock irrespective of the position of the circuit breaker, which have a restricted access to a skilled maintenance personal. WE CLAIM: 1. Door interlocking system for an electrical switching apparatus, the said switching apparatus being mounted on an enclosed housing, comprising: a door lock on the housing of the switching apparatus; a sensor assembly configured to determine the position of the switching apparatus based on a plurality of markings on the switching apparatus, wherein the markings constitutes various positions of the switching apparatus; and a controller electrically connected to said sensor assembly and configured to control the locking or unlocking of the door of the housing of the switching apparatus relating to the position of the switching apparatus. 2. The system as claimed in claim 2, wherein said sensor assembly comprises a transmitter for transmitting sensing signal on said plurality of markings and ,a receiver for receiving the sensing signal reflected from said plurality of markings. 3. The system as claimed in claim 1, wherein said sensor assembly is an optical sensor assembly or ultrasonic depth sensor assembly. 4. The system as claimed in claim 1, 2 and 3, wherein the said markings are configured with varying widths or depths. 5. The system as claimed in claim 3, wherein said optical assembly measures the intensity of light beam reflected back from the markings and generates a signal corresponding to the measured intensity of the reflected light to identify the position of the switching apparatus. 6. The system as claimed in claim 6, wherein the generated signal determines the width of the markings which relates to position of the switching apparatus 7. The system as claimed in claim 3, wherein said ultrasonic assembly measures the intensity of ultrasonic wave reflected back from the markings and generates a signal corresponding to the measured intensity of the reflected wave to identify the position of the switching apparatus. 8. The system as claimed in claim 9, wherein the generated signal determines the depth of the markings which relates to position of the switching apparatus. 9. The system as claimed in claim 1, wherein the markings on the switching apparatus relates to the positions of said switching apparatus defining the working, test or isolated state of the switching apparatus. 10. The system as claimed in claim 1, comprising a display unit electrically connected to the controller for displaying the detected positions of the circuit breaker. 11. The system as claimed in claim 1, wherein said sensor assembly placed at a desired location along a guiding path of the circuit breaker. 12. The system as claimed in claim 1, wherein once the switching apparatus is drawn out .from working state at a predetermined location, the controller activates the stopping means to restrict the movement of the circuit breaker back to the working pr test position. 13. The system as claimed in claim 1 wherein said controller determines the state of the door, and when the door is locked, said controller deactivates the stopping means and allows the further movement of the switching apparatus back to the working position.

Full Text

DOOR INTERLOCKING SYSTEM FOR AN ELECTRICAL SWITCHING APPARATUS

FIELD OF THE INVENTION

The present invention relates to the fields of electrical switching apparatus. The present invention specifically relates to a door interlocking system for controlling access to a circuit breaker housing.

BACKGROUND OF THE INVENTION

In general, electrical switching apparatus used in power distribution systems are mounted within a housing assembly either individually or in combination with other switchgears such as circuit breakers. Some electrical switching apparatus, particularly low voltage circuit breakers are quite large, (n order to facilitate movement during installation, removal and maintenance, the circuit breaker is commonly coupled to rollers/racking mechanism, which permit such circuit breaker to be drawn out of the housing assembly. This circuit breaker is commonly known as draw-out type circuit breaker/such apparatus.

Referring to FIG. 1, a schematic view of various operations of a draw out type circuit breaker 1 is illustrated, in accordance with prior art. During operation, the draw out type circuit breaker 1 exhibits four positions, such as Working, Test, Isolated and Disconnected, in the switchboard. The circuit breaker 1 can be mounted on a mounting plate 5 assembled to the switchboard frame 4. In working position, the circuit breaker 1 is connected to the main power supply 2 as well as to the auxiliary supply, which ensures that the circuit breaker 1 is in normal working condition, as shown in FIG. 1a. In test position, the main power supply 2 is disconnected but auxiliary supply is still connected to the circuit breaker 1, as shown in FIG. lb. This position is used to test the functionality of the auxiliary circuit. Moreover, in isolated position, both the main power supply 2 and the auxiliary supply are disconnected from the circuit breaker 1, as shown in FIG. 1c. Clearance between the circuit breaker terminal and the busbar 3 is more than or equal to isolation distance, where servicing of the circuit breaker 1 is done in this position. Finally, in disconnected position, the circuit breaker 1 is disconnected both electrically and mechanically from the switchboard.

In order to prevent injury, e.g. electrical shock, it is often desirable to limit access to the circuit breaker 1 within the housing. Such circuit breaker 1 must be drawn out of the housing to access and perform maintenance.

Improper maintenance procedures, i.e. failure to turn OFF the circuit breaker 1, cause serious injury to maintenance personnel and damage to the electrical equipment during arc flashover while the door 6 being opened. Hence, while withdrawing the circuit breaker 1 from the switchboard, it is essential to retain the switchboard door 6, as shown in FIG. 2, in locked condition until the circuit breaker reaches the isolated position. In case of pushing in, the door should be locked, once the circuit breaker 1 crosses the isolated position. This type of interlocking system is mandatory to protect the operator from the electrical hazards.
There are few electrical and mechanical interlocking systems available in the switchboards. But these types of interlocking systems are either device specific or switchboard specific. Further, the existing door locking system could be manually manipulated by maintenance personnel such that the door locking is rendered ineffective. Also the existing Mechanical Interlocks can be made inactive during certain circumstances by tying the locking lever by a string. Such procedures not only make the mechanical interlock useless but also obstruct the very safety feature of the mechanical interlock which is intended.

FIG. 2 shows a schematic view of existing door interlocking systems, in accordance with prior art. Referring to FIG. 2a, a mechanical interlocking system utilizes a number of mechanical linkages. Also over a period of time the linkages may be subjected to lot of wear and tear and may not properly engage the door
lock, thereby requiring some manual adjustments with the link mechanisms. Such mechanical interlocking system cannot be used for others equipments, since it is designed depending on the mechanism of a particular type of circuit breakers. Referring to FIG. 2b, an electrical interlocking system requires some additional wiring in the switchboard to operate an electrical door lock 7 and it is also breaker specific.

With respect to the conventional door interlocking systems, it is very complicated and not adaptable to any circuit breakers or any switchboards. Moreover, the mechanical door interlock uses complex mechanisms, and consists of lots; of moving parts which become cumbersome during maintenance. Therefore, it is essential to design a simple and efficient door interlocking system to overcome the above-mentioned drawbacks.

OBJECT OF THE INVENTION

An object of the present invention is to provide a door interlocking system for controlling access to a circuit breaker housing, which prevents serious injury to maintenance personnel and damage to the electrical equipment.

Another object of the present invention is to provide a door interlocking system for controlling access to a circuit breaker housing, which is adaptable to any switchboard and any circuit breaker.

A further object of the present invention is to provide a door interlocking system for controlling access to a circuit breaker housing, which is easy to operate and involves less wear and tear due to very few mechanical moving parts.

SUMMARY OF THE INVENTION

According to one aspect, the present invention, which achieves this objective, relates to a door interlocking system for an electrical switching apparatus mounted on an enclosed housing, comprising a door lock on the housing of the switching apparatus. A sensor assembly is configured to determine the position of the switching apparatus based on markings on the switching apparatus, where the markings constitute various positions of the switching apparatus. A controller is electrically connected to the sensor assembly and configured to control the locking or unlocking of the door of the housing of the switching apparatus relating to the position of the switching apparatus. Such interlocking system prevents serious injury to maintenance personnel and
damage to the electrical equipment. Also, it is adaptable to any switchboard and any switching apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be discussed in greater detail with reference to the accompanying Figures.

FIG. 1 shows a schematic view of various operations of a draw out type circuit breaker, in accordance with prior art;

FIG. 2 illustrates a schematic view of existing door interlocking systems, in accordance with prior art;

FIG. 3 illustrates an isometric view depicting location of a sensor assembly of a door interlocking system, in accordance with an,exemplary embodiment of the present invention;

FIG. 4: illustrates a schematic view of the door interlocking system with a circuit breaket" assembled on a mounting plate, in accordance with an exemplary embodiment of the present invention;

FIG. 5 illustrates a schematic view showing working principle of an optical sensor, in accordance with an exemplary embodiment of the present invention;

FIG. 6- illustrates a significance of cryptogram for an ultrasonic depth sensor, in accordance with an exemplary embodiment of the present invention;

FIG. 7 illustrates a functional block diagram of the door interlocking system, in accordance with an exemplary embodiment of the present invention;

FIG. 8 illustrates a flow chart showing the sequence of operation of the door interlocking system while drawing out the circuit breaker, in accordance with an exemplary embodiment of the present invention; and

FIG. 9 illustrates a flow chart showing the sequence of operation of the door interlocking system while pushing in the circuit breaker, in accordance with an exemplary'embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 3, an isometric view depicting location of a sensor assembly 106 of a door interlocking system, in accordance with an exemplary embodiment of the present invention. A drawn out type circuit breaker 101 can be mounted on a mounting plate 102, which is connected to a switchboard frame 103. The door interlocking system can optically monitor the positional status of the drawn out type circuit breaker 101 with respect to working, test and isolated status. The system comprises a sensor assembly 106 placed at a strategic location along the guiding path of the withdrawable circuit breaker 101 to detect the position of the circuit breaker 101.

In addition, the sensor assembly 106 includes a transmitter 106a and a receiver 106b placed in tandem arrangement on any side of the enclosure. Generally, the transmitter 106a consists of a light source (visible light beam or laser beam or infrared beam) and the receiver 106b consists of a photo diode or any other photovoltaic cells or optical sensor or camera, which are placed next to each other in a defined location. The light 105 emitted by the transmitter 106a is tuned to a specific frequency and the receiver 106b is designed to detect only the tuned frequency light corresponding to cryptogram markings 104 placed on the circuit breaker 101.
FIG. 4 illustrates a schematic view of the door interlocking system with the circuit breaker 101 assembled on the mounting plate 102, in accordance with an exemplary embodiment of the present invention. For example, let us consider that the optical sensor 106 is utilized the door interlocking system. In order to sense the position of the circuit breaker 101, a cryptogram 104 is pasted on the side of the circuit breaker 101 in relation to the position of the optical transmitter 106a and the optical receiver 106b. The cryptogram 104 contains three black bars 104a, 104b and 104c, where each bar varies in width, but not in height, as shown in FIG. 5, which illustrates a schematic view showing working principle of the optical sensor 106, in accordance with an exemplary embodiment of the present invention. The preferred cryptograms 104 are placed sequentially on either side of the circuit breaker 101 in in-line form. Such cryptograms 104 have to be placed in a defined position with respect to the desired positions of the circuit breaker 101.
Furthermore, the optical transmitter 106a, i.e. light source, transmits the light beam 105 falling on the black bars 104a, 104b and 104c of the cryptogram 104 to read the position of the circuit breaker 101. The positions of the black bars 104a, 104b and 104c with respect to the optical sensor 106 are calibrated in such a way that the transmitted light beam 105 falls on the black bar 104a if the circuit breaker 101 is in working position, on the black bar 104b if the breaker 101 is in test position ana on ine oiacK oar la m louiaicu (JWOIUM, as shown in FIGS. 4a, 4b and 4c, respectively. Then, the optical receiver 106b, i.e. photo diode, measures the intensity of the light reflected back from the respective black bars black bar 104a, 104b and 104c of the cryptogram 104 and generates a voltage waveform signal corresponding to the measured intensity of the reflected light, as shown in FIG. 5.

The generated waveform signal can be used to measure the widths of the black bars 104a, 104b and 104c and spaces in the cryptogram 104, which defines the exact position (working, test or isolation position) of the circuit breaker 101, as clearly explained in FIG. 5. The dark black bars 104a, 104b and 104c in the cryptogram 104 absorb the light 105 whereas the white spaces reflect the light 105, so that the voltage waveform signal generated by the photo diode 106b is an exact replica of the bar and space pattern in the cryptogram 104.

Moreover, the optical sensors are limited to specific environments like home, commercial buildings, etc, since it is not suitable for harsh environments with risk of blockage due to external materials, e.g. dust. Particularly, such optical sensor for position detection is not suitable if the switchboard is placed in a harsh environment and if the atmosphere contains lots of dust particles (fly ash, smoke and sawdust), which are very common in manufacturing industries. In such case, ultrasonic depth sensors can be used, since it exhibits high accuracy even in harsh environment. In case of ultrasonic depth sensor, the cryptogram 111 placed in the circuit breaker 101 can be modified to make it as ultrasonic wave sensitive. Such cryptogram 111 contains three blind rectangular cuts 111a, 111b and 111c of varying depth, namely A1, A2 and A3, as shown in FIG. 6, which illustrates a significance of cryptogram for the ultrasonic depth sensor, in accordance with an exemplary embodiment of the present invention.

The ultrasonic wave falls on these rectangular cuts 111a, 111b and 111c and measures the depth. The position of the cuts 111a, 111b and 111c is
calibrated such a way that ultrasonic wave falls on the depth A1, which concludes that the breaker 101 is in connected or working condition. Similarly, the depths A2 and A3 conclude that the breaker 101 is in test condition and isolated condition, respectively. Hence, the optical detection can be used for indoor installation for buildings, hospitals, hotels etc., whereas the ultrasonic detection is efficient for shop floor of manufacturing industries and power plant, which exhibits huge variation of temperature and harsh environment with lots of dust particles.

Referring to FIG. 7, a functional block diagram of the door interlocking system is illustrated, in accordance with an exemplary embodiment of the present invention. The sensor assembly 106 reads the input from the cryptogram 104 placed on the circuit breaker 101, i.e. after reading the width or depth of the cryptogram. The sensor assembly 106 transmits an output signal to a controller 108, as shown in FIGS. 4 and 7, where the output signal is in the form of voltage waveform. The controller 108 decodes the voltage waveform signal in a manner similar to the way Morse code dots and dashes are decoded. The controller 108 also analyses the position of the breaker 101 and generates a command in relation to the analyzed breaker position.

Further, the controller 108 is programmed to send the command to an electromagnetic lock 109 so as to allow opening/closing of the switchboard door depending upon the signal received from the optical sensor assembly 106. The electromagnetic door lock 109 is placed on the top of enclosure of the electrical switching apparatus for locking the front door of the switchboard or panel. The door lock 109 is energized into locked or unlocked states for closing or opening of the switchboard door, respectively. For the purpose of clear explanation, the discussion, examples and illustrations set forth in this specification deal with electromagnetic door lock, but as explained hereinabove, my novel system is not limited to such, but comprises other types of door lock. Moreover, the controller 108 initially traces the position of the circuit breaker 101 by measuring the width or depth of the cryptogram 104 and the output is displayed on an LCD display 110. The LCD display 110 displays the current position of the circuit breaker 101 to maintenance personnel.

FIG. 8 illustrates a flow chart showing the sequence of operation of the door interlocking system while drawing out the circuit breaker, in accordance with an exemplary embodiment of the present invention. While drawing out the circuit breaker 101, the breaker 101 should be disconnected electrically and mechanically from the switchboard. In this phenomenon, initially the breaker 101 is in working condition and the door is in locked state. As illustrated in step 801, the sensor assembly 106 reads the position of the circuit breaker 101. In particular, the sensor 106 reads the bar 104a or cut 111a and the LCD 110 displays the breaker position as 'WORKING', as depicted in step 802.

Similarly, when the breaker 101 is drawn to test condition, the sensor 106 read the bar 104b or cut 111b and the LCD 110 displays the position as TEST'. When the breaker 101 is drawn to isolated condition, the sensor 106 read the bar 104c or cut 111c and the LCD 110 displays the position as 'ISOLATED'. As shown in step 803, the controller 108 checks that the breaker 101 is reached the isolated position. If the breaker 101 is not reached the isolated position, the controller 108 sends the command to the electromagnetic lock 109 to retain it in locked condition and checks for the signal from the sensor 106, as illustrated in step 806. If the breaker 101 is reached the isolated position, the controller 108 sends a signal to the electromagnetic lock 109 to unlock the door and activates the mechanical stopper to ensure an additional safety, as shown in steps 804 and 805. Such mechanical stopper is triggered and activated by certain actuator, which allows the breaker to be pushed in from isolated position unless and until the door is in closed position. Thereafter, the breaker 101 can be completely removed from the switchboard.

FIG. 9 illustrates a flow chart showing the sequence of operation of the door interlocking system while pushing in the circuit breaker, in accordance with an exemplary embodiment of the present invention. While pushing in the circuit breaker 101, the breaker 101 should be assembled back inside the switchboard. In this case, initially the door is in unlocked condition and the LCD 110 displays the position as 'ISOLATED'. As illustrated in step 901, the sensor assembly 106 reads the position of the circuit breaker 101. As shown in step 902, the LCD 110 displays the position of the breaker 101 as isolated or test or working. As shown in step 903, checking is made whether the breaker 101 is reached the isolated position. If the breaker 101 is not reached the isolated position, the controller 108 checks for the signal from the sensor 106, as illustrated in step 907.
As illustrated in steps 904 and 905, once the circuit breaker 101 crosses the isolated position i.e. it is pushed further in, the controller 108 checks whether the door is locked and sends a signal to the electromagnetic lock 109 to keep the door in locked condition. Then, the circuit breaker 101 traverses to test position and the LCD 110 displays the position as 'TEST, the lock retains the door closed. Finally, the circuit breaker 101 reaches working condition and the LCD 110 displays the position as 'WORKING'. The circuit breaker 101 touches the Busbar of power supply 107 and gets ready to work. The controller 108 keeps the door in locked condition. As illustrated in step 906, the controller 108 deactivates the mechanical stopper to engaging the circuit breaker back into working condition if the door is in locked state. If the door is in unlocked state, the mechanical stopper not allows the breaker 101 to push in, as depicted in step 907.

While drawing out the circuit breaker 101 from the connections, a stopping means 112, like mechanical stopper, is activated once the breaker 101 crosses a predetermined position. In the present embodiment, the predetermined position is defined as the test position. This stopping means 112 once activated restricts the movement of the circuit breaker 101 back to the working condition. In order to engage the circuit breaker 101 back to the working position, the stopping means 112 should be deactivated. This deactivation of the stopping means 112 is controlled by the controller 108. The controller 108 is configured such that, on meeting of certain criteria it deactivates the stopping means 112 and thus allowing the movement of the circuit breaker 101 back to the working condition. The controller 108 is configured to receive input from the electromagnetic lock 109 on the condition of locking. When the electromagnetic lock 109 is in the locked, the controller 108 deactivates the stopping means 112 and thus allows movement of circuit breaker 101. I The optical/ultrasonic sensor and the electromagnetic door lock are easily installed at any preferred location. This interlocking system is made to withdraw the current either directly from the incomer (using some step down transformer) or through a rechargeable battery placed exclusively for this purpose. The required amount of power to operate the electromagnetic door lock is 12 V/ 500 mA. One of the significant advantages of this interlocking system is that there are no moving parts involved unlike the conventional mechanical linkages, so thereby it is easy to operate and also involves less wear and tear. Moreover, such interiocking system is adaptable to any switchboard and any circuit breaker. In case of emergency, an optional electrical switch can be provided to deactivate the electromagnetic lock irrespective of the position of the circuit breaker, which have a restricted access to a skilled maintenance personal.

WE CLAIM:

1. Door interlocking system for an electrical switching apparatus, the said
switching apparatus being mounted on an enclosed housing, comprising:

a door lock on the housing of the switching apparatus;

a sensor assembly configured to determine the position of the switching apparatus based on a plurality of markings on the switching apparatus, wherein the markings constitutes various positions of the switching apparatus; and

a controller electrically connected to said sensor assembly and configured to control the locking or unlocking of the door of the housing of the switching apparatus relating to the position of the switching apparatus.

2. The system as claimed in claim 2, wherein said sensor assembly comprises a transmitter for transmitting sensing signal on said plurality of markings and ,a receiver for receiving the sensing signal reflected from said plurality of markings.

3. The system as claimed in claim 1, wherein said sensor assembly is an optical sensor assembly or ultrasonic depth sensor assembly.

4. The system as claimed in claim 1, 2 and 3, wherein the said markings are configured with varying widths or depths.

5. The system as claimed in claim 3, wherein said optical assembly measures the intensity of light beam reflected back from the markings and generates a signal corresponding to the measured intensity of the reflected light to identify the position of the switching apparatus.

6. The system as claimed in claim 6, wherein the generated signal determines the width of the markings which relates to position of the switching apparatus

7. The system as claimed in claim 3, wherein said ultrasonic assembly measures the intensity of ultrasonic wave reflected back from the markings and generates a signal corresponding to the measured intensity of the reflected wave to identify the position of the switching apparatus.

8. The system as claimed in claim 9, wherein the generated signal determines the depth of the markings which relates to position of the switching apparatus.

9. The system as claimed in claim 1, wherein the markings on the switching apparatus relates to the positions of said switching apparatus defining the working, test or isolated state of the switching apparatus.

10. The system as claimed in claim 1, comprising a display unit electrically
connected to the controller for displaying the detected positions of the circuit
breaker.

11. The system as claimed in claim 1, wherein said sensor assembly placed at a desired location along a guiding path of the circuit breaker.

12. The system as claimed in claim 1, wherein once the switching apparatus
is drawn out .from working state at a predetermined location, the controller activates the stopping means to restrict the movement of the circuit breaker back to the working pr test position.

13. The system as claimed in claim 1 wherein said controller determines the state of the door, and when the door is locked, said controller deactivates the stopping means and allows the further movement of the switching apparatus back to the working position.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=ToyHrg2PbZdgDgOPXjvIRQ==&loc=egcICQiyoj82NGgGrC5ChA==

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Patent Number

279213

Indian Patent Application Number

1345/CHE/2009

PG Journal Number

03/2017

Publication Date

20-Jan-2017

Grant Date

16-Jan-2017

Date of Filing

08-Jun-2009

Name of Patentee

SCHNEIDER ELECTRIC INDUSTRIES SAS

Applicant Address

35 RUE JOSEPH MONIER, F-92500 RUEIL MALMAISON

Inventors:

#	Inventor's Name	Inventor's Address
1	GAUTAM LALANKERE	GLOBAL TECHNOLOGY CENTRE, #88(P), II FLOOR, SAHASRA SHREE EPIP INDUSTRIAL AREA, NEXT TO VYDEHI HOSPITAL, WHITEFIELD, BANGALORE 560 066
2	MANAN DEB	GLOBAL TECHNOLOGY CENTRE, #88(P), II FLOOR, SAHASRA SHREE EPIP INDUSTRIAL AREA, NEXT TO VYDEHI HOSPITAL, WHITEFIELD, BANGALORE 560 066

PCT International Classification Number

E05B

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA