FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF INVENTION
Electromagnetic drive mechanism for a switching device
APPLICANTS
Name : CROMPTON GREAVES LIMITED
Nationality: Indian Company
Address : CG House, Dr Annie Besant Road, Worli, Mumbai 400030, Maharashtra, India
INVENTOR:
Gan Nikhil Purushottam, Crompton Greaves Ltd, Technology Cell, Switchgear Division, A2 MIDC, Ambad, Nashik 422010, Maharashtra, India, an Indian National
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

FIELD OF INVENTION
This invention relates to an electromagnetic drive mechanism for a switching device.
PRIOR ART DESCRIPTION
Switching devices like circuit breakers or contactors are generally closed or opened by an electromagnetic drive mechanism so as to allow or interrupt the flow of current in the electric circuits in which the switching devices are used. Such switching devices generally handle voltages upto 33kV. A typical electromagnetic drive mechanism comprises an armature reciprocally located within a magnetic material core and a pair of electromagnetic circuits. The armature includes an actuator rod coaxially located therein and connected to the moving electrode of the switching device. One of the electromagnetic circuits comprises a first electromagnetic coil in series with a first voltage source and an electronic closing switch. The first electromagnetic coil is located around the upper portion of the armature. The other electromagnetic circuit comprises a second electromagnetic coil in series with a second voltage source and an electronic tripping switch. The second electromagnetic coil is located around the lower portion of the armature. The electromagnetic coils are operated sequentially ie one after the other and independently to move the armature up and down and close and trip the contacts of the switching device. Usually the first and second voltage sources each comprises a pair of capacitors. The energy requirement of the coils for moving the armature will depend upon the operating stroke of the armature and the rating of the switching device. The higher the operating stroke of the armature and rating of the switching device, the higher the energy requirement of the coils. Since the coils are operated independently of each other, energy requirement for moving the armature is very high, especially in the case of high voltage switching devices. This considerably increases the size and rating and energy storage capacity of the
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capacitors and the other components of the electromagnetic circuits and also both the capital and operating costs of the drive mechanism. Due to switching surges at high voltage operations, the closing and tripping switches are prone to failures. This reduces the reliability of the drive mechanism.
OBJECTS OF INVENTION
An object of the invention is to provide an electromagnetic drive mechanism for a switching device, which mechanism makes optimal utilization of energy so as to achieve improved performance and efficiency with reduced voltage and to reduce the size and rating and energy storage capacity of the drive mechanism and to reduce the capital and operating costs of the drive mechanism.
Another object of the invention is to provide an electromagnetic drive mechanism for a switching device, which has improved reliability.
DETAILED DESCRIPTION OF INVENTION
According to the invention there is provided an electromagnetic drive mechanism for a switching device, the drive mechanism comprising an armature reciprocally located within a magnetic material core and an electromagnetic circuit for moving the armature up and down to close and trip the contacts of the switching device, the electromagnetic circuit comprising a pair of electromagnetic coils, one coil located around the upper portion of the armature and the other coil located around the lower portion of the armature, the coils being wound around the armature and being electrically coupled to each other in such a manner that current flows through the coils in the same direction in a shared manner and that the
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fluxes generated in the armature by the coils are in the same direction and aiding each other, a closing circuit connected at one junction between the coils and comprising a first voltage source, a first relay and an electronic closing switch in series and a tripping circuit connected at the other junction between the coils and comprising a second voltage source, a second relay and an electronic tripping switch in series.
According to the invention there is also provided a method a of making an electromagnetic drive mechanism for a switching device, the method comprising configuring an armature reciprocally located within a magnetic material core and further configuring an electromagnetic circuit for moving the armature up and down to close and trip the contacts of the switching device, the electromagnetic circuit comprising a pair of electromagnetic coils, one coil located around the upper portion of the armature and the other coil located around the lower portion of the armature, the coils being wound around the armature and being electrically coupled to each other in such a manner that current flows through the coils in the same direction in a shared manner and that the fluxes generated in the armature by the coils are in the same direction and aiding each other, a closing circuit connected at one junction between the coils and comprising a first voltage circuit, a first relay and an electronic closing switch in series and a tripping circuit connected at the other junction between the coils and comprising a second voltage source, a second relay and an electronic tripping switch in series.
The following is a detailed description of the invention with reference to the accompanying drawings, in which:
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Fig 1 is a schematic crossectional view of the electromagnetic drive mechanism for a switching device according to an embodiment of the invention; and
Fig 2 is the electrical circuit of the drive mechanism of Fig 1.
The drive mechanism 1 as illustrated in the accompanying drawings comprises an armature 2 reciprocally located within a magnetic material core 3. The armature includes an actuator rod 4 coaxially located therein and connected to the moving electrode (not shown) of the switching device (not shown). The drive mechanism also comprises a pair of electromagnetic coils 5 and 6. Coil 5 is located around the upper portion of the armature and coil 6 is located around the lower portion of the armature. A first voltage source 7, a first relay 8 and an electronic closing switch 9 in series are connected at one junction between the coils. A second voltage source 10, a second relay 11 and an electronic tripping switch 12 in series are connected at the other junction between the coils. 13 is a permanent magnet located around the middle portion of the armature and between the electromagnetic coils. The coils are wound around the armature and electrically coupled to each other in such a manner that when the capacitor 7 or 10 discharges current flows through the coils in the same direction in a shared manner and that the fluxes generated by the coils in the armature are in the same direction and are aiding each other. During the contact closing operation of the switching device, the electronic controller (not shown) of the switching device closes the relay 11 and closing switch 9. The capacitor 10 starts discharging and a current flows through the coils 5 and 6 and the closing switch 9. Due to energization of the coils magnetic fluxes generated in the armature by the coils also flow in the same direction and aid each other. As a result an increased motive force is exerted on the armature and the armature is pulled up to close the contacts of the switching device. During the contact
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tripping operation of the switching device, the electronic controller of the switching device closes the relay 8 and tripping switch 12. The capacitor 7 starts discharging and a current flows through the coils 5 and 6 and the tripping switch 12. Due to energisation of the coils magnetic fluxes generated in the armature by the coils also flow in the same direction and aid each other. As a result an increased motive force is exerted on the armature and the armature is pulled down so as to trip the contacts of the switching device.
According to the invention both the electromagnetic coils are in circuit and the current is shared by the coils during both the closing and tripping operations of the switching device. Energy available is utilized by both the coils optimally in both the operations so as to generate maximum magnetic flux and motive force to move the armature up and down. Therefore, the performance and efficiency of the drive mechanism is improved. High energies can be generated at low voltage levels. With the sharing of the current by the coils and generation of maximum magnetic fluxes in the same direction and maximum power output as taught by the invention it should be possible to reduce by about 50% the voltage requirement of the drive mechanism of the invention for generating the same electromagnetic force as compared to an equivalent conventional electromagnetic drive mechanism. Stroke of the armature and electromagnetic force generation by the drive mechanism are increased for a given energy input. Due to generation of increased electromagnetic force with reduced voltage it is possible to reduce the size and rating and energy consumption of the electronic switches of the drive mechanism and to reduce the rating of the capacitors and to reduce the capital and operating cost of the drive mechanism. The magnetic drive mechanism of the invention is suitable for use in switching devices of higher ratings like 52 kV and above so as to realize maximum savings in energy and cost and reduction in size. As the operating voltage levels are reduced switching surges are
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reduced. Vulnerability of the closing and tripping switches to failures is reduced and the reliability of the drive mechanism is improved. Preferably the first and second voltage sources each comprises a single capacitor and the electronic closing switch and electronic tripping switch each comprises metal oxide semi conductor field effect transistors (MOSFETs), insulated gate bipolar transistors (IGBTs), thyristors or solid state relays. It is to be, however, clearly understood that the first and second voltage sources each may comprise more than one capacitor.
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We claim:
1. An electromagnetic drive mechanism for a switching device, the drive mechanism comprising an armature reciprocally located within a magnetic material core and an electromagnetic circuit for moving the armature up and down to close and trip the contacts of the switching device, the electromagnetic circuit comprising a pair of electromagnetic coils, one coil located around the upper portion of the armature and the other coil located around the lower portion of the armature, the coils being wound around the armature and being electrically coupled to each other in such a manner that current flows through the coils in the same direction in a shared manner and that the fluxes generated in the armature by the coils are in the same direction and aiding each other, a closing circuit connected at one junction between the coils and comprising a first voltage source, a first relay and an electronic closing switch in series and a tripping circuit connected at the other junction between the coils and comprising a second voltage source, a second relay and an electronic tripping switch in series.
2. The drive mechanism as claimed in claim 1, wherein the first and second voltage sources each comprises a capacitor and the electronic closing switch and electronic tripping switch each comprises metal oxide semiconductor field effect transistors(MOSFETs), insulated gate bipolar transistors (IGBTs), thyristors or solid state relays.
3. A method of making an electromagnetic drive mechanism for a switching device, the method comprising configuring an armature reciprocally located within a magnetic material core and further configuring an electromagnetic circuit for moving the armature up and down to close and trip the contacts of the switching device, the electromagnetic circuit comprising a pair of electromagnetic coils, one coil located around the upper portion of the
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armature and the other coil located around the lower portion of the armature, the coils being wound around the armature and being electrically coupled to each other in such a manner that current flows through the coils in the same direction in a shared manner and that the fluxes generated in the armature by the coils are in the same direction and aiding each other, a closing circuit connected at one junction between the coils and comprising a first voltage circuit, a first relay and an electronic closing switch in series and a tripping circuit connected at the other junction between the coils and comprising a second voltage source, a second relay and an electronic tripping switch in series.
4. The method as claimed in claim 1, wherein the first and second voltage sources each comprises a capacitor and the electronic closing switch and electronic tripping switch each comprises metal oxide semiconductor field effect transistors (MOSFETs), insulated gate bipolar transistors (IGBTs), thyristors or solid state relays.
Dated this 22nd day of June 2007.

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Abstract
An electromagnetic drive mechanism (1) for a switching device. The drive mechanism comprises an armature (2) reciprocally located within a magnetic material core (3) and an electromagnetic circuit for moving the armature up and down to close and trip the contacts of the switching device. The electromagnetic circuit comprises a pair of electromagnetic coils, one coil (5) located around the upper portion of the armature and the other coil (6) located around the lower portion of the armature. The coils are wound around the armature and are electrically coupled to each other in such a manner that current flows through the coils in the same direction in a shared manner and that the fluxes generated in the coils are in the same direction and are aiding each other. A closing circuit connected at one junction between the coils comprises a first voltage source (7), a first relay (8) and an electronic closing switch (9) in series. A tripping circuit connected at the other junction between the coils comprises a second voltage source (10), a second relay (11) and an electronic tripping switch (12) in series. (Figs 1 and 2).