Title of Invention	"DEVICE FOR CLOSING OF CONTACTS OF A CIRCUIT BREAKER"
Abstract	Accordingly, the present invention provides an energy efficient device for closing of contacts of a circuit breaker that is based on the principal of pneumatic closing, pneumatic holding and spring opening. In addition to being energy efficient, the device of the present invention eliminates substantial number of mechanical components and also eliminates substantial active and passive components in the electronic control unit thereby improving the reliability of the operation of the device, reducing the manufacturing cost and enhancing ease of manufacturing.

Title of Invention

"DEVICE FOR CLOSING OF CONTACTS OF A CIRCUIT BREAKER"

Abstract

Accordingly, the present invention provides an energy efficient device for closing of contacts of a circuit breaker that is based on the principal of pneumatic closing, pneumatic holding and spring opening. In addition to being energy efficient, the device of the present invention eliminates substantial number of mechanical components and also eliminates substantial active and passive components in the electronic control unit thereby improving the reliability of the operation of the device, reducing the manufacturing cost and enhancing ease of manufacturing.

Full Text	DEVICE FOR CLOSING OF CONTACTS OF A CIRCUIT BREAKER Field of the Invention: The present invention relates to a device for closing of contacts of a circuit breaker. More particularly, the present invention relates to a device for closing of contacts of a vacuum circuit breaker provided in an electric traction vehicle. Background and Prior Art Description: As shown in figure 1, in an electric traction vehicle (10), the current is drawn from an overhead catenary (11) via a pantograph bus bar connection (12) and consumed for propulsion of the electric traction vehicle (10). For the purpose of controlling the current drawn from the overhead catenary (11), a circuit breaker (14) is included between the pantograph bus bar connection (12) and a traction transformer (13). The circuit breaker (14) thus included is a vacuum circuit breaker. The vacuum circuit breaker (VCB) (14) is of single phase and has a rating of about 25kV AC and is used to protect power circuit applied on electric locomotives and electric multiple units (EMUs). In other words, the VCB (14) is used to disconnect the vehicle (10) from the overhead catenary (11), in the event of overload or short-circuit current conditions or any other abnormal working conditions defined and implemented for the applications on vehicle (10). The VCB (14) is intended for installation on the roof of a traction vehicle (10) to carry current from the pantograph bus bar connection (12) to one end of a vacuum interrupter and from other end of the vacuum interrupter to a roof bushing of a loco transformer. The design and implementation of the VCB is preferably adapted to the requirements and working conditions of electric traction vehicle and service condition on Railways. The VCB utilizes vacuum to extinguish arcing when the circuit breaker is opened and to act as a dielectric to insulate the contacts after the arc is interrupted. More details regarding construction of the VCB can be found in Indian Patent Application No. 738/MAS/1994. The vacuum circuit breaker consists of three main parts: (a) An upper part, which is a high voltage circuit (HT); (b) An intermediate part, which assures isolation from earth; and (c) A lower part having control and drive mechanism. The VCB is designed in such a way that upper part and the intermediate part are located over the roof of the traction vehicle and are exposed to the open atmosphere whereas the lower part is under the roof of the traction vehicle. With reference to figure 2, it can be noticed that the circuit breaker and more particularly the vacuum circuit breaker comprises of vacuum switch tube (28) a movable contact (29) and a fixed contact (30). For the purpose of opening and closing contacts (29 and 30) of the vacuum circuit breaker (14), a control and drive mechanism is used. One of the control and drive mechanism used is described in US Patent Number 5,298,702 (corresponding to Indian Patent Application Number 523/MAS/1992), the contents of which are herein incorporated as reference. The diagram of control and drive mechanism described in the aforesaid US Patent is provided as figure 2 for the purpose of easy of reference. The drive mechanism (20) contains a pressure medium reservoir (21), a drive piston (22) which slides in a drive cylinder (23) and acts on a mechanism (24) for displacing a movable contact (29) of the vacuum switch tube. During a first phase of operation of the drive mechanism, i.e. during the process of closing the contacts, the pressure medium contained in the pressure medium reservoir (21) is supplied to the drive cylinder (23), which displaces the drive piston (22) in an upward direction so as to move the movable contact (29) towards the fixed contact (30) and at an extreme upward location of the drive piston (22) closes the contacts. During the first phase, the pressure medium displaces the drive piston (22) against the force exerted by a spring mechanism (25) and a vacuum pressure existing between the two contacts (29 and 30). Once the contacts are closed, a second phase of operation of the drive mechanism begins. • In the second phase of the operation of the drive mechanism, the moving contact (29) must be kept in locked state with respect to the fixed contact (30). For the purpose of keeping the contacts locked, a holding coil (26) located substantially above the drive cylinder is energized so long as contact supply is available and holds the drive piston (22) in the extreme upward location i.e. where the contacts (29 and 30) get closed. After the closing of contacts, an interposed valve (27) disposed between the pressure medium reservoir (21) and the drive cylinder (23) is actuated and the pressure medium contained in the drive cylinder (23) is released. The actuation of the interposed valve (27) and the activation of the holding coil (26) are done by an electronic circuit (31) (shown in figure 3). A third phase of operation of the drive mechanism is actuated to interrupt the power circuit current and to open the contacts under overload or short-circuit current conditions or any other abnormal working conditions defined and implemented for the applications. In order to open the contacts (29 and 30) of the circuit breaker, the locking of the contacts (29 and 30) is first cancelled by de-energizing the holding coil (26) through the electronic circuit (31) (refer to figures 2 and 3). The force of the loaded spring (25) automatically and instantaneously pushes the drive piston (22) in a downward direction from the extreme upward location to an extreme downward location. Due to the motion of the drive piston from the extreme upward location to the extreme downward location, the movable contact (29) which is connected to the piston moves into a switched off position of the circuit breaker. Thus, the operation of the above-mentioned contact breaker can be said to be based on the following principle: (a) pneumatic (air pressure) closing (b) electromagnetic (coil) holding and (c) mechanical (spring action) opening. It can be noticed that the above-mentioned circuit breaker is operated using electro-pneumatic based drive and control system. The drive and the control system utilizes large number of components that work in the voltage range of 6V-30V DC (such as 12V DC coils, 24 V DC coils etc.). A person skilled would be aware, the battery provided in the locomotive supply energy in the form of 110V / 72V / 24V DC and hence use of the mentioned components necessitates, conditioning of locomotive battery supply, which results in complete waste of the energy. Since, the coil used for keeping the contacts in the closed state is required to be supplied the power almost during the entire operation of the circuit breaker, a large amount of energy is wasted by (a) the operation of the coil and (b) for the purpose of conditioning of the locomotive battery supply. In addition, the passive and active components used in the electronic control unit (in spite of the fact that these components had adequate margin) were prone to malfunction / failure and were the major contributor for occasional failures of the VCB. The drive and control system is designed such that the movable contact (29) and the fixed contact (30) are brought in contact with each other at a controlled rate. For the purpose of controlling the speed at which movable contact (29) and the fixed contact (30) are brought in contact, a freely movable rod shaped member is located in a chamber which is provided in the flow path between the reservoir and the drive cylinder. At the beginning of the contact making operation, the rod shaped member throttles the flow cross-section of the chamber. The pressure medium passes through the chamber at a controlled rate and displaces the drive piston in a controlled rate in the upward direction, thereby displacing the movable contact. The rod shaped member is connected via a linking mechanism such that it moves at a controlled rate in an upward direction along with the motion of the piston and out of the chamber, thereby enlarging the flow of cross section. The linking mechanism does not experience any undesired load and stress as long as the working conditions are free of vibrations. However, under vibrating working conditions (as would exist in a vehicle), the linking mechanism experiences load/stress and hence tend to break/malfunction. Therefore, there exists a long felt need to provide a device for closing and opening the contacts of a circuit breaker that simplifies the need of power conditioning, provides enhanced reliability, overcome afore-said drawbacks and at the same time minimizes the power consumption. Objects of the Invention: The main object of the present invention is to provide a device for closing and opening the contacts of a circuit breaker that obviates at least one of the disadvantages mentioned in the foregoing paragraphs. Brief description of the accompanying drawings: In order that the invention may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying drawings, where like reference numerals refer to identical or functionally similar elements throughout the separate views. The figures together with a detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, in accordance with the present invention where: Figure 1 shows an electrical traction vehicle. Figure 2 shows a circuit breaker according to the prior art. Figure 3 illustrates a schematic of typical electronic control in the prior art circuit breaker. Figure 4 is an exemplary illustration of a vacuum circuit breaker according to the present invention. Figure 4(a) is an exemplary illustration of closing of contacts of a vacuum circuit breaker according to the present invention. Figure 4(b) illustratively shows vacuum circuit breaker in hold position according to the present invention. Figure 4(c) is an exemplary illustration of opening of contacts of a vacuum circuit breaker according to the present invention. Figure 5 is exemplary illustration of connection circuit for control circuit of vacuum circuit breaker according to the present invention. Skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the drawings may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention. Summary of the Invention: Accordingly, the present invention provides an energy efficient device for closing of contacts of a circuit breaker that is based on the principal of pneumatic closing, pneumatic holding and spring opening. In addition to being energy efficient, the device of the present invention eliminates substantial number of mechanical components and also eliminates substantial active and passive components in the electronic control unit thereby improving the reliability of the operation of the device, reducing the manufacturing cost and enhancing ease of manufacturing. Statement of the Invention: The present invention provides a device for closing of contacts of a circuit breaker, comprising: a vacuum switch tube consisting of a fixed contact and a moving contact; a reservoir for storing compressed air; a pneumatic cylinder being connected to the reservoir, said pneumatic cylinder housing a slidable piston which is connected to the movable contact of vacuum switch tube; and an exhaust region being in communication with the said pneumatic cylinder; characterized in that, a predetermined quantity of the compressed air contained in the reservoir is introduced into the pneumatic cylinder for moving the piston in the upward direction to an extreme upward location thereby closing the contacts and for holding the piston in the said extreme upward location; and the air contained in the pneumatic cylinder is expelled to the exhaust region to open the contacts; and the pneumatic cylinder is formed with an air flow regulating device for moving the piston at a controlled rate in the upward direction within the pneumatic cylinder. Detailed description of the Present Invention: Accordingly, the present invention relates to a device for closing of contacts of a circuit breaker, comprising: a vacuum switch tube consisting of a fixed contact and a moving contact; a reservoir for storing compressed air; a pneumatic cylinder being connected to the reservoir, said pneumatic cylinder housing a slidable piston which is connected to the movable contact of vacuum switch tube; and an exhaust region being in communication with the said pneumatic cylinder; characterized in that, a predetermined quantity of the compressed air contained in the reservoir is introduced into the pneumatic cylinder for moving the piston in the upward direction to an extreme upward location thereby closing the contacts and for holding the piston in the said extreme upward location; and the air contained in the pneumatic cylinder is expelled to the exhaust region to open the contacts; and the pneumatic cylinder is formed with an air flow regulating device for moving the piston at a controlled rate in the upward direction within the pneumatic cylinder. In an embodiment of the present invention, the reservoir and the exhaust region are connected to the said pneumatic cylinder by a common channel. In another embodiment of the present invention, the common channel comprises at least one inlet port and at least one outlet port and a displaceable valve for controlling the flow of the compressed air through the said ports. In still another embodiment of the present invention, the displaceable valve comprises a first closing means displaceable with respect to the inlet port and a second closing means displaceable with respect to the outlet port. In yet another embodiment of the present invention, the displaceable valve is actuated by means of a motorized mechanism or an electromagnetic mechanism or a spring actuated mechanism or combinations thereof. • In a further embodiment of the present invention, the first closing means and second closing means are arranged to close the inlet port and open the outlet port synchronously and vice versa. In further more embodiment of the present invention, the inlet port and the first closing means are configured such that by the operation of said first closing means, the compressed air from reservoir is brought at a location (x) in a common channel at a first rate. In another embodiment of the present invention, the air flow regulating device comprises at least one orifice formed at about a bottom/downward location of the pneumatic cylinder for controlling the flow of the air entering into the pneumatic cylinder at a second rate. In yet another embodiment of the present invention, the first rate is substantially greater than the second rate. In one another embodiment of the present invention the size of the orifice is selected according to the desired rate of upward motion of the piston. In a further embodiment of the present invention the piston is provided with a projection wherein the dimension of the projection is specifically configured with respect to the dimension of the orifice formed/provided in the pneumatic cylinder for controlling the second flow rate. In one more embodiment of the present invention a compression spring is further provided to control the rate of upward motion of the piston. Detailed Description of Embodiments Before describing in detail embodiments that are in accordance with the present invention, it should be observed that nothing contained in this section is intended to limit the scope of the invention. The scope of the invention is intended to be limited purely by the claims and its equivalence. The following detailed description of the embodiments is provided purely to enhance the understanding of the invention and to assist a person reading the document to work the invention. Accordingly, the elements (or in other words the components) of the device have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein. The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a device that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such device. Also, it should be observed that an element proceeded by "comprises... a" does not, without more constraints, preclude the existence of additional identical elements in the device that comprises the element. The present invention is described with reference to the figures and specific embodiments; this description is not meant to be construed in a limiting sense. Various alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such alternative embodiments form part of the present invention. Figures 4, 4(a), 4(b) and 4(c) show various kinematics schemes of the device for closing contacts of a circuit breaker in accordance with some of the alternative embodiments of the present invention. The device of the present invention comprises a vacuum switch tube (80) consisting of a fixed contact (90) and a movable contact (150) and a reservoir (100) for storing compressed air. The reservoir may be provided with a pressure regulator with a filter (110) and a pressure switch (120) for monitoring minimum pressure. The reservoir (100) is arranged to be brought in fluid flow communication with a pneumatic cylinder (130). The pneumatic cylinder (130) houses a slidable piston (140) which is coupled to the movable contact (150) of the vacuum switch tube (80) through a drive mechanism (160). The pneumatic cylinder (130) is arranged to be brought in fluid flow communication with an exhaust region (170) which can be atmosphere or an outer space. The reservoir (100) and the exhaust region (170) are brought in flow communication with the pneumatic cylinder (130) by a common channel (180). The common channel (180) is provided with an inlet port (190) and an outlet port (200). A displaceable valve (210) is placed in the common channel for regulating the flow of the compressed air through said ports. There can be more than one inlet ports and the outlet ports. The displaceable valve (210) is actuated by an actuating mechanism (220) such as a motorized mechanism or an electromagnetic mechanism or a spring mechanism or combinations thereof. The displaceable valve (210) comprises a first closing means (230) and a second closing means (240). The first closing means (230) is displaceable with respect to the inlet port (190) and the second closing means (240) is displaceable with respect to the outlet port (200). The first closing means (230) and the second closing means (240) are arranged to close the inlet port (190) and open the outlet port (200) synchronously and vice versa. The first closing means (230) and the second closing means (240) are arranged such that outlet port (200) remains closed till the inlet port (190) remains open and similarly, the inlet port (190) remains closed till the outlet port (200) remains open. Initially, the inlet port (190) is closed and the outlet port (200) is open. When the current is required to be drawn from the overhead catenary, the actuating mechanism (220) is energized, as shown in figure 4(a). By the energization of the actuating mechanism (220), the second closing means (240) closes the outlet port (200) and the first closing means (230) opens the inlet port (190), thereby bringing the reservoir (100) in fluid flow communication with the pneumatic cylinder (130). When the inlet port (190) is opened, the compressed air contained in the reservoir (100) reaches to a location X in the common channel at a first rate. Since the pneumatic cylinder is provided with an orifice (250) at a bottom location, the compressed air enters the pneumatic cylinder (130) through the orifice (250) at a second rate, wherein the first rate is substantially greater than the second rate. Since the second rate is substantially lesser than the first rate, movement of the moving contact (150) is at a controlled speed and preferably at a desired slow rate. It is further envisaged that the piston (140) is provided with a projection (260) for closing insertable into the orifice (250) when the piston (140) is at its lowermost location. The projection (260) is an optional feature, which further helps in regulating the flow of the compressed air inside the pneumatic cylinder (130), especially in the initial phase of closing of circuit breaker. The controlled flow of compressed air regulates the speed of the moving contact (150) as required for reliable operation of the vacuum switch tube and to reduce bouncing back. The size of the orifice (250) is so designed that it will ensure satisfactory performance of vacuum circuit breaker by maintaining specified slow closing speed. The entry of the compressed air into the pneumatic cylinder (130) apply pressure on the piston (140) which actuates the drive mechanism (160) to displace the moving contact (150) to close the contact. Once the piston (140) reaches at the top or extreme upward location of the pneumatic cylinder (130) the contacts are closed. During closing of contacts the compression spring (270, 280) fitted in drive mechanism (160) becomes charged. The circuit breaker is held closed by holding the moving piston (140) at the extreme upward location by not allowing the air to release from the pneumatic cylinder (130). Figure 4(b) illustrates holding of piston (140) at the extreme upward location in the pneumatic cylinder (130). The contacts are closed for desired period of time. To open the contacts, the pneumatic cylinder (130) is brought in fluid flow communication with the exhaust region (170). This is achieved by de-energisation of actuating mechanism (220). By de-energisation of the actuating mechanism (220), the first closing means (230) actuates to close the inlet port (190) of the common channel (180) and the second closing means (240) simultaneously opens the outlet port (200) to bring the pneumatic cylinder (130) in flow communication with the exhaust region (170). Size of the outlet port (200) is larger than the size of the inlet port (190). Therefore, the rate of outflow of the exhausted air is higher than the rate of inflow of air during contact closing such that to match the characteristics of vacuum switch tube (80). The compression springs (270, 280) which are charged during closing of contacts release their stored energy to revert back the whole drive mechanism (160) connected to the moving contact (150) to its initial open position. Figure 4(c) illustrates the initiation of the opening of contacts and figure 4 illustrates the opened condition of the contacts. Figure 5 illustrates control circuit configuration for the device according to the present invention. The foregoing detailed description has described only a few of the many possible implementations of the present invention. Thus, the detailed description is given only by way of illustration and nothing contained in this section should be construed to limit the scope of the invention. We Claim: 1. A device for closing of contacts of a circuit breaker, comprising: a vacuum switch tube consisting of a fixed contact and a moving contact; a reservoir for storing compressed air; a pneumatic cylinder being connected to the reservoir, said pneumatic cylinder housing a slidable piston which is connected to the movable contact of vacuum switch tube; and an exhaust region being in communication with the said pneumatic cylinder; characterized in that, a predetermined quantity of the compressed air contained in the reservoir is introduced into the pneumatic cylinder for moving the piston in the upward direction to an extreme upward location thereby closing the contacts and for holding the piston in the said extreme upward location; and the air contained in the pneumatic cylinder is expelled to the exhaust region to open the contacts; and the pneumatic cylinder is formed with an air flow regulating device for moving the piston at a controlled rate in the upward direction within the pneumatic cylinder. 2. The device as claimed in claim 1, wherein the reservoir and the exhaust region are connected to the said pneumatic cylinder by a common channel. 3. The device as claimed in any one of the preceding claims 1 and 2, wherein the common channel comprises at least one inlet port and at least one outlet port and a displaceable valve for controlling the flow of the compressed air through the said ports. 4. The device as claimed in any one of the preceding claims 1 to 3, wherein the displaceable valve comprises a first closing means displaceable with respect to the inlet port and a second closing means displaceable with respect to the outlet port. 5. The device as claimed in any one of the preceding claims 1 to 4, wherein the displaceable valve is actuated by means of a motorized mechanism or an electromagnetic mechanism or a spring mechanism or combinations thereof. 6. The device as claimed in any one of the preceding claims 1 to 5, wherein the first closing means and second closing means are arranged to close the inlet port and open the outlet port synchronously and vice versa. 7. The device as claimed in any one of the preceding claims 1 to 6, wherein the inlet port and the first closing means are configured such that by the operation of said first closing means, the compressed air from the reservoir is brought at a location (x) in a common channel at a first rate. 8. The device as claimed in any one of the preceding claims 1 to 7, wherein the air flow regulating device comprises at least one orifice formed at about a bottom/downward location of the pneumatic cylinder for controlling the flow of the air entering into the pneumatic cylinder at a second rate. 9. The device as claimed in any one of the preceding claims 1 to 8, wherein the first rate is substantially greater than the second rate. 10. The device as claimed in any one of the preceding claims 1 to 9, wherein the size of the orifice is selected according to the desired rate of upward motion of the piston. 11. The device as claimed in any one of the preceding claims 1 to 10, wherein the piston is provided with a projection wherein the dimension of the projection specifically configured and matched with dimension of the orifice formed/provided in the pneumatic cylinder for controlling the second flow rate. 12. The device as claimed in any one of the preceding claims 1 to 11, wherein a compression spring is further provided to control the rate of upward motion of the piston. 13. A device for closing of contacts of a circuit breaker substantially as herein described with reference to the accompanying drawings.

Full Text

DEVICE FOR CLOSING OF CONTACTS OF A CIRCUIT
BREAKER
Field of the Invention:
The present invention relates to a device for closing of contacts of a circuit breaker. More particularly, the present invention relates to a device for closing of contacts of a vacuum circuit breaker provided in an electric traction vehicle.
Background and Prior Art Description:
As shown in figure 1, in an electric traction vehicle (10), the current is drawn from an overhead catenary (11) via a pantograph bus bar connection (12) and consumed for propulsion of the electric traction vehicle (10). For the purpose of controlling the current drawn from the overhead catenary (11), a circuit breaker (14) is included between the pantograph bus bar connection (12) and a traction transformer (13). The circuit breaker (14) thus included is a vacuum circuit breaker. The vacuum circuit breaker (VCB) (14) is of single phase and has a rating of about 25kV AC and is used to protect power circuit applied on electric locomotives and electric multiple units (EMUs). In other words, the VCB (14) is used to disconnect the vehicle (10) from the overhead catenary (11), in the event of overload or short-circuit current conditions or any other abnormal working conditions defined and implemented for the applications on vehicle (10).
The VCB (14) is intended for installation on the roof of a traction vehicle (10) to carry current from the pantograph bus bar connection (12) to one end of a vacuum interrupter and from other end of the vacuum interrupter to a roof bushing of a loco transformer. The design and implementation of the VCB is preferably adapted to the requirements and working conditions of electric traction vehicle and service condition on Railways.
The VCB utilizes vacuum to extinguish arcing when the circuit breaker is opened and to act as a dielectric to insulate the contacts after the arc is interrupted. More details regarding construction of the VCB can be found in Indian Patent Application No. 738/MAS/1994. The vacuum circuit breaker consists of three main parts:
(a) An upper part, which is a high voltage circuit (HT);
(b) An intermediate part, which assures isolation from earth; and
(c) A lower part having control and drive mechanism.
The VCB is designed in such a way that upper part and the intermediate part are located over the roof of the traction vehicle and are exposed to the open atmosphere whereas the lower part is under the roof of the traction vehicle.
With reference to figure 2, it can be noticed that the circuit breaker and more particularly the vacuum circuit breaker comprises of vacuum switch tube (28) a movable contact (29) and a fixed contact (30). For the purpose of opening and closing contacts (29 and 30) of the vacuum circuit breaker (14), a control and drive mechanism is used. One of the control and drive mechanism used is described in US Patent Number 5,298,702 (corresponding to Indian Patent Application Number 523/MAS/1992), the contents of which are herein incorporated as reference. The diagram of control and drive mechanism described in the aforesaid US Patent is provided as figure 2 for the purpose of easy of reference.
The drive mechanism (20) contains a pressure medium reservoir (21), a drive piston (22) which slides in a drive cylinder (23) and acts on a mechanism (24) for displacing a movable contact (29) of the vacuum switch tube.
During a first phase of operation of the drive mechanism, i.e. during the process of closing the contacts, the pressure medium contained in the pressure medium reservoir (21) is supplied to the drive cylinder (23), which displaces the drive piston (22) in an upward direction so as to move the movable contact (29) towards the fixed contact (30) and at an extreme upward location of the drive piston (22) closes the contacts. During the first phase, the pressure medium displaces the drive piston (22) against the force exerted by a spring mechanism (25) and a vacuum pressure existing between the two contacts (29 and 30). Once the contacts are closed, a second phase of operation of the drive mechanism begins.
• In the second phase of the operation of the drive mechanism, the moving contact (29) must be kept in locked state with respect to the fixed contact (30). For the purpose of keeping the contacts locked, a holding coil (26) located substantially above the drive cylinder is energized so long as contact supply is available and holds the drive piston (22) in the extreme upward location i.e. where the contacts (29 and 30) get closed. After the closing of contacts, an interposed valve (27) disposed between the pressure medium reservoir (21) and the drive cylinder (23) is actuated and the pressure medium contained in the drive cylinder (23) is released. The actuation of the interposed valve (27) and the activation of the holding coil (26) are done by an electronic circuit (31) (shown in figure 3).
A third phase of operation of the drive mechanism is actuated to interrupt the power circuit current and to open the contacts under overload or short-circuit current conditions or any other abnormal working conditions defined and implemented for the applications. In order to open the contacts (29 and 30) of the circuit breaker, the locking of the contacts (29 and 30) is first cancelled by de-energizing the holding coil (26) through the electronic circuit (31) (refer to figures 2 and 3). The force of the loaded spring (25) automatically and instantaneously pushes the drive piston (22) in a downward direction from the extreme upward location to an extreme downward location. Due to the motion of the drive piston from the extreme upward location to the extreme downward location, the movable contact (29) which is connected to the piston moves into a switched off position of the circuit breaker.
Thus, the operation of the above-mentioned contact breaker can be said to be based on the following principle:
(a) pneumatic (air pressure) closing
(b) electromagnetic (coil) holding and
(c) mechanical (spring action) opening.
It can be noticed that the above-mentioned circuit breaker is operated using electro-pneumatic based drive and control system. The drive and the control system utilizes large
number of components that work in the voltage range of 6V-30V DC (such as 12V DC coils, 24 V DC coils etc.). A person skilled would be aware, the battery provided in the locomotive supply energy in the form of 110V / 72V / 24V DC and hence use of the mentioned components necessitates, conditioning of locomotive battery supply, which results in complete waste of the energy. Since, the coil used for keeping the contacts in the closed state is required to be supplied the power almost during the entire operation of the circuit breaker, a large amount of energy is wasted by (a) the operation of the coil and (b) for the purpose of conditioning of the locomotive battery supply. In addition, the passive and active components used in the electronic control unit (in spite of the fact that these components had adequate margin) were prone to malfunction / failure and were the major contributor for occasional failures of the VCB.
The drive and control system is designed such that the movable contact (29) and the fixed contact (30) are brought in contact with each other at a controlled rate. For the purpose of controlling the speed at which movable contact (29) and the fixed contact (30) are brought in contact, a freely movable rod shaped member is located in a chamber which is provided in the flow path between the reservoir and the drive cylinder. At the beginning of the contact making operation, the rod shaped member throttles the flow cross-section of the chamber. The pressure medium passes through the chamber at a controlled rate and displaces the drive piston in a controlled rate in the upward direction, thereby displacing the movable contact. The rod shaped member is connected via a linking mechanism such that it moves at a controlled rate in an upward direction along with the motion of the piston and out of the chamber, thereby enlarging the flow of cross section. The linking mechanism does not experience any undesired load and stress as long as the working conditions are free of vibrations. However, under vibrating working conditions (as would exist in a vehicle), the linking mechanism experiences load/stress and hence tend to break/malfunction.
Therefore, there exists a long felt need to provide a device for closing and opening the contacts of a circuit breaker that simplifies the need of power conditioning, provides
enhanced reliability, overcome afore-said drawbacks and at the same time minimizes the power consumption.
Objects of the Invention:
The main object of the present invention is to provide a device for closing and opening the contacts of a circuit breaker that obviates at least one of the disadvantages mentioned in the foregoing paragraphs.
Brief description of the accompanying drawings:
In order that the invention may be readily understood and put into practical effect,
reference will now be made to exemplary embodiments as illustrated with reference to
the accompanying drawings, where like reference numerals refer to identical or
functionally similar elements throughout the separate views. The figures together with a
detailed description below, are incorporated in and form part of the specification, and
serve to further illustrate the embodiments and explain various principles and advantages,
in accordance with the present invention where:
Figure 1 shows an electrical traction vehicle.
Figure 2 shows a circuit breaker according to the prior art.
Figure 3 illustrates a schematic of typical electronic control in the prior art circuit
breaker.
Figure 4 is an exemplary illustration of a vacuum circuit breaker according to the present
invention.
Figure 4(a) is an exemplary illustration of closing of contacts of a vacuum circuit breaker
according to the present invention.
Figure 4(b) illustratively shows vacuum circuit breaker in hold position according to the
present invention.
Figure 4(c) is an exemplary illustration of opening of contacts of a vacuum circuit
breaker according to the present invention.
Figure 5 is exemplary illustration of connection circuit for control circuit of vacuum
circuit breaker according to the present invention.
Skilled artisans will appreciate that elements in the drawings are illustrated for simplicity
and have not necessarily been drawn to scale. For example, the dimensions of some of
the elements in the drawings may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
Summary of the Invention:
Accordingly, the present invention provides an energy efficient device for closing of contacts of a circuit breaker that is based on the principal of pneumatic closing, pneumatic holding and spring opening. In addition to being energy efficient, the device of the present invention eliminates substantial number of mechanical components and also eliminates substantial active and passive components in the electronic control unit thereby improving the reliability of the operation of the device, reducing the manufacturing cost and enhancing ease of manufacturing.
Statement of the Invention:
The present invention provides a device for closing of contacts of a circuit breaker, comprising:
a vacuum switch tube consisting of a fixed contact and a moving contact;
a reservoir for storing compressed air;
a pneumatic cylinder being connected to the reservoir, said pneumatic cylinder housing a slidable piston which is connected to the movable contact of vacuum switch tube; and
an exhaust region being in communication with the said pneumatic cylinder;
characterized in that,
a predetermined quantity of the compressed air contained in the reservoir is introduced into the pneumatic cylinder for moving the piston in the upward direction to an extreme upward location thereby closing the contacts and for holding the piston in the said extreme upward location; and the air contained in the pneumatic cylinder is expelled to the exhaust region to open the contacts; and the pneumatic cylinder is formed with an air flow regulating device for moving the piston at a controlled rate in the upward direction within the pneumatic cylinder.
Detailed description of the Present Invention:
Accordingly, the present invention relates to a device for closing of contacts of a circuit breaker, comprising:
a vacuum switch tube consisting of a fixed contact and a moving contact;
a reservoir for storing compressed air;
a pneumatic cylinder being connected to the reservoir, said pneumatic cylinder housing a slidable piston which is connected to the movable contact of vacuum switch tube; and
an exhaust region being in communication with the said pneumatic cylinder;
characterized in that,
a predetermined quantity of the compressed air contained in the reservoir is introduced into the pneumatic cylinder for moving the piston in the upward direction to an extreme upward location thereby closing the contacts and for holding the piston in the said extreme upward location; and the air contained in the pneumatic cylinder is expelled to the exhaust region to open the contacts; and the pneumatic cylinder is formed with an air flow regulating device for moving the piston at a controlled rate in the upward direction within the pneumatic cylinder.
In an embodiment of the present invention, the reservoir and the exhaust region are connected to the said pneumatic cylinder by a common channel.
In another embodiment of the present invention, the common channel comprises at least one inlet port and at least one outlet port and a displaceable valve for controlling the flow of the compressed air through the said ports.
In still another embodiment of the present invention, the displaceable valve comprises a first closing means displaceable with respect to the inlet port and a second closing means displaceable with respect to the outlet port.
In yet another embodiment of the present invention, the displaceable valve is actuated by means of a motorized mechanism or an electromagnetic mechanism or a spring actuated mechanism or combinations thereof.
• In a further embodiment of the present invention, the first closing means and second closing means are arranged to close the inlet port and open the outlet port synchronously and vice versa.
In further more embodiment of the present invention, the inlet port and the first closing means are configured such that by the operation of said first closing means, the compressed air from reservoir is brought at a location (x) in a common channel at a first rate.
In another embodiment of the present invention, the air flow regulating device comprises at least one orifice formed at about a bottom/downward location of the pneumatic cylinder for controlling the flow of the air entering into the pneumatic cylinder at a second rate.
In yet another embodiment of the present invention, the first rate is substantially greater than the second rate.
In one another embodiment of the present invention the size of the orifice is selected according to the desired rate of upward motion of the piston.
In a further embodiment of the present invention the piston is provided with a projection wherein the dimension of the projection is specifically configured with respect to the dimension of the orifice formed/provided in the pneumatic cylinder for controlling the second flow rate.
In one more embodiment of the present invention a compression spring is further provided to control the rate of upward motion of the piston.
Detailed Description of Embodiments
Before describing in detail embodiments that are in accordance with the present invention, it should be observed that nothing contained in this section is intended to limit the scope of the invention. The scope of the invention is intended to be limited purely by the claims and its equivalence. The following detailed description of the embodiments is
provided purely to enhance the understanding of the invention and to assist a person reading the document to work the invention. Accordingly, the elements (or in other words the components) of the device have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein. The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a device that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such device. Also, it should be observed that an element proceeded by "comprises... a" does not, without more constraints, preclude the existence of additional identical elements in the device that comprises the element.
The present invention is described with reference to the figures and specific embodiments; this description is not meant to be construed in a limiting sense. Various alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such alternative embodiments form part of the present invention.
Figures 4, 4(a), 4(b) and 4(c) show various kinematics schemes of the device for closing contacts of a circuit breaker in accordance with some of the alternative embodiments of the present invention. The device of the present invention comprises a vacuum switch tube (80) consisting of a fixed contact (90) and a movable contact (150) and a reservoir (100) for storing compressed air. The reservoir may be provided with a pressure regulator with a filter (110) and a pressure switch (120) for monitoring minimum pressure. The reservoir (100) is arranged to be brought in fluid flow communication with a pneumatic cylinder (130). The pneumatic cylinder (130) houses a slidable piston (140) which is coupled to the movable contact (150) of the vacuum switch tube (80) through a drive mechanism (160). The pneumatic cylinder (130) is arranged to be brought in fluid flow communication with an exhaust region (170) which can be atmosphere or an outer space.

The reservoir (100) and the exhaust region (170) are brought in flow communication with the pneumatic cylinder (130) by a common channel (180).
The common channel (180) is provided with an inlet port (190) and an outlet port (200). A displaceable valve (210) is placed in the common channel for regulating the flow of the compressed air through said ports. There can be more than one inlet ports and the outlet ports. The displaceable valve (210) is actuated by an actuating mechanism (220) such as a motorized mechanism or an electromagnetic mechanism or a spring mechanism or combinations thereof. The displaceable valve (210) comprises a first closing means (230) and a second closing means (240). The first closing means (230) is displaceable with respect to the inlet port (190) and the second closing means (240) is displaceable with respect to the outlet port (200). The first closing means (230) and the second closing means (240) are arranged to close the inlet port (190) and open the outlet port (200) synchronously and vice versa. The first closing means (230) and the second closing means (240) are arranged such that outlet port (200) remains closed till the inlet port (190) remains open and similarly, the inlet port (190) remains closed till the outlet port (200) remains open.
Initially, the inlet port (190) is closed and the outlet port (200) is open. When the current is required to be drawn from the overhead catenary, the actuating mechanism (220) is energized, as shown in figure 4(a). By the energization of the actuating mechanism (220), the second closing means (240) closes the outlet port (200) and the first closing means (230) opens the inlet port (190), thereby bringing the reservoir (100) in fluid flow communication with the pneumatic cylinder (130). When the inlet port (190) is opened, the compressed air contained in the reservoir (100) reaches to a location X in the common channel at a first rate. Since the pneumatic cylinder is provided with an orifice (250) at a bottom location, the compressed air enters the pneumatic cylinder (130) through the orifice (250) at a second rate, wherein the first rate is substantially greater than the second rate. Since the second rate is substantially lesser than the first rate, movement of the moving contact (150) is at a controlled speed and preferably at a desired slow rate.
It is further envisaged that the piston (140) is provided with a projection (260) for closing insertable into the orifice (250) when the piston (140) is at its lowermost location. The projection (260) is an optional feature, which further helps in regulating the flow of the compressed air inside the pneumatic cylinder (130), especially in the initial phase of closing of circuit breaker.
The controlled flow of compressed air regulates the speed of the moving contact (150) as required for reliable operation of the vacuum switch tube and to reduce bouncing back. The size of the orifice (250) is so designed that it will ensure satisfactory performance of vacuum circuit breaker by maintaining specified slow closing speed. The entry of the compressed air into the pneumatic cylinder (130) apply pressure on the piston (140) which actuates the drive mechanism (160) to displace the moving contact (150) to close the contact. Once the piston (140) reaches at the top or extreme upward location of the pneumatic cylinder (130) the contacts are closed. During closing of contacts the compression spring (270, 280) fitted in drive mechanism (160) becomes charged.
The circuit breaker is held closed by holding the moving piston (140) at the extreme upward location by not allowing the air to release from the pneumatic cylinder (130). Figure 4(b) illustrates holding of piston (140) at the extreme upward location in the pneumatic cylinder (130).
The contacts are closed for desired period of time. To open the contacts, the pneumatic cylinder (130) is brought in fluid flow communication with the exhaust region (170). This is achieved by de-energisation of actuating mechanism (220). By de-energisation of the actuating mechanism (220), the first closing means (230) actuates to close the inlet port (190) of the common channel (180) and the second closing means (240) simultaneously opens the outlet port (200) to bring the pneumatic cylinder (130) in flow communication with the exhaust region (170). Size of the outlet port (200) is larger than the size of the inlet port (190). Therefore, the rate of outflow of the exhausted air is higher than the rate of inflow of air during contact closing such that to match the characteristics of vacuum switch tube (80). The compression springs (270, 280) which are charged during closing of contacts release their stored energy to revert back the whole drive mechanism (160)
connected to the moving contact (150) to its initial open position. Figure 4(c) illustrates the initiation of the opening of contacts and figure 4 illustrates the opened condition of the contacts.
Figure 5 illustrates control circuit configuration for the device according to the present invention.
The foregoing detailed description has described only a few of the many possible implementations of the present invention. Thus, the detailed description is given only by way of illustration and nothing contained in this section should be construed to limit the scope of the invention.

We Claim:
1. A device for closing of contacts of a circuit breaker, comprising:
a vacuum switch tube consisting of a fixed contact and a moving contact;
a reservoir for storing compressed air;
a pneumatic cylinder being connected to the reservoir, said pneumatic cylinder housing a slidable piston which is connected to the movable contact of vacuum switch tube; and
an exhaust region being in communication with the said pneumatic cylinder;
characterized in that,
a predetermined quantity of the compressed air contained in the reservoir is introduced into the pneumatic cylinder for moving the piston in the upward direction to an extreme upward location thereby closing the contacts and for holding the piston in the said extreme upward location; and the air contained in the pneumatic cylinder is expelled to the exhaust region to open the contacts; and the pneumatic cylinder is formed with an air flow regulating device for moving the piston at a controlled rate in the upward direction within the pneumatic cylinder.
2. The device as claimed in claim 1, wherein the reservoir and the exhaust region are
connected to the said pneumatic cylinder by a common channel.
3. The device as claimed in any one of the preceding claims 1 and 2, wherein the
common channel comprises at least one inlet port and at least one outlet port and
a displaceable valve for controlling the flow of the compressed air through the
said ports.
4. The device as claimed in any one of the preceding claims 1 to 3, wherein the
displaceable valve comprises a first closing means displaceable with respect to the
inlet port and a second closing means displaceable with respect to the outlet port.
5. The device as claimed in any one of the preceding claims 1 to 4, wherein the
displaceable valve is actuated by means of a motorized mechanism or an
electromagnetic mechanism or a spring mechanism or combinations thereof.
6. The device as claimed in any one of the preceding claims 1 to 5, wherein the first
closing means and second closing means are arranged to close the inlet port and
open the outlet port synchronously and vice versa.
7. The device as claimed in any one of the preceding claims 1 to 6, wherein the inlet
port and the first closing means are configured such that by the operation of said
first closing means, the compressed air from the reservoir is brought at a location
(x) in a common channel at a first rate.
8. The device as claimed in any one of the preceding claims 1 to 7, wherein the air
flow regulating device comprises at least one orifice formed at about a
bottom/downward location of the pneumatic cylinder for controlling the flow of
the air entering into the pneumatic cylinder at a second rate.
9. The device as claimed in any one of the preceding claims 1 to 8, wherein the first
rate is substantially greater than the second rate.
10. The device as claimed in any one of the preceding claims 1 to 9, wherein the size
of the orifice is selected according to the desired rate of upward motion of the
piston.
11. The device as claimed in any one of the preceding claims 1 to 10, wherein the
piston is provided with a projection wherein the dimension of the projection
specifically configured and matched with dimension of the orifice
formed/provided in the pneumatic cylinder for controlling the second flow rate.
12. The device as claimed in any one of the preceding claims 1 to 11, wherein a
compression spring is further provided to control the rate of upward motion of the
piston.
13. A device for closing of contacts of a circuit breaker substantially as herein
described with reference to the accompanying drawings.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=dVs0nrB48pq4Fo6EJalEFg==&loc=+mN2fYxnTC4l0fUd8W4CAA==

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Patent Number

269207

Indian Patent Application Number

2015/DEL/2006

PG Journal Number

42/2015

Publication Date

16-Oct-2015

Grant Date

09-Oct-2015

Date of Filing

11-Sep-2006

Name of Patentee

AUTOMETERS ALLIANCE LTD.

Applicant Address

C-63, SECTOR 57, NOIDA-201307, UTTAR PRADESH, INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	DIGAMBAR PRASAD BHATT	C-63, SECTOR 57, NOIDA-201307, UTTAR PRADESH, INDIA
2	RANDHIR SINGH	C-63, SECTOR 57, NOIDA-201307, UTTAR PRADESH, INDIA

PCT International Classification Number

H01H71/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA