FORM 2
The Patents Act 1970
(39 of 1970)
&
The Patent Rules 2003
COMPLETE SPECIFICATION
(See Section 10 and rule 13) TITLE OF THE INVENTION:
UNDER VOLTAGE RELEASE SYSTEM WlTH LOW POWER CONSUMPTION FOR CIRCUIT BREAKER
APPLICANT:
LARSEN & TOUBRO LIMITED
L&T House, Ballard Estate, P.O. Box No. 278,
Mumbai, 400 001, Maharashtra . INDIA.
PREAMBLE OF THE DESCRIPTION:
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

A) TECHNICAL FIELD
[0001] The present invention generally relates to circuit breakers and
particularly to air circuit breakers. The present invention more particularly relates to to under voltage release in air circuit breakers
B) BACKGROUND OF THE INVENTION
[0002] The circuit breakers are used for main power distribution in large
industrial plants. The circuit breakers protect electrical circuit from overload, under-voltage, earth fault, over current and short circuit damages. The electrical circuit is benefited from under voltage release by disconnecting the main power distribution during under voltage or power failure occurs, wherein the under-voltage is referred to as voltage below a specified limit through out description of the invention.
[0003] The under-voltage releases include electromagnet connected to the
power supply of the circuit breaker. Under healthy supply condition when the voltage is above the specific limit the electro magnet remains closed. In case the voltage drops below the specific limit or during power failure the electro-magnet drops off. This drop off mechanism of the electro magnet is utilized for tripping the circuit breakers under low voltage conditions to protect the electrical circuit.


[0004] The under-voltage release includes a direct current (DC) power operated
electromagnet system. The electromagnet system has a fixed-magnet, a spring loaded movable magnet and a coil around the two magnets. The two magnets stay apart before the DC supply is fed into the coil, this is referred to as open-magnet position. When the DC power passes through the coil, the coil builds up an electro magnetic field. In presence of the electro magnetic field, the spring loaded movable magnet moves towards the fixed magnet to establish contact with the fixed magnet and remains touching the fixed magnet, as long as the voltage is above the specified limit, this is refereed to as closed-magnet position. The closed magnet position is utilized to switch ON the circuit breaker. The movable magnet moving from open-magnet position to close-magnet position is called pick-up of the magnet. The movable magnet moving from close-magnet position to open-magnet position is called drop¬off of the magnet, and holding the movable magnet in close-magnet position is called hold-on position of the magnet.
[0005] The coil draws large amount of power to close the magnets from open-
magnet position to closed-magnet position. The power required to hold the magnets in closed-magnet position is much lower. However, the excess power drawn by the coil remains unchanged, unless it is controlled. The excess power drawn by the coil is a loss. Further, the excess power generates lot of heat and problems related to elevated temperature.
[0006] The currently available system includes a dual coil, a dual spring, a pick-
up circuit, a hold-on circuit and an electronic circuit used to switch from a pick-up


circuit to a hold-on circuit. The pick-up circuit is used for closing the electromagnet. Once the magnets are closed, the circuit switches from the pick-up circuit to the hold on circuit. The hold-on circuit may draw optimum amount of power required to keep the magnets closed and may avoid the problem of power loss and heat generation. However, the arrangement still consumes considerable power to over come spring force employed to store the energy required to trip of the breaker circuit. Further, the system continuously monitors the power supply and gives a drop-off command when the power supply voltage drops below a specified limit Hence, in light of foregoing discussion there exists a need to provide a simple under-voltage release delivering higher force and still consume negligible power, generating less heat for applications to enhance reliability and higher life of a electrical device and associated equipments of the electrical device.
[0007] The abovementioned shortcomings, disadvantages and problems are
addressed herein and which will be understood by reading and studying the following specification.
C) OBJECT OF THE INVENTION
[0008] The primary object of the present invention is to provide a simple under-
voltage release for air circuit breakers to reduce power loss due to excess power consumption, reduce heat generation.


[0009] Another object of the present invention is to provide an under-voltage
release delivering power proportionate to difference between magnet power and spring power, where the spring power is higher than holding force of the magnet.
[0010] Yet another object of the present invention is to provide an under-
voltage release to enhance reliability and higher fife of a electrical device and associated equipments of the electrical device.
[0011] These and other objects and advantages of the present invention will
become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
D) SUMMARY OF THE INVENTION
[0012] The various embodiments of the present invention provide a simple
under-voltage release for air circuit breakers to reduce power loss due to excess power consumption, reduce heat generation. The under-voltage release delivers power proportionate to difference between magnet power and spring power, where the spring power is higher than holding force of the magnet.
[0013] According to one embodiment of the present invention, an under
voltage release system with low power consumption for circuit breaker has a magnetic frame housing in which a permanent magnet is arranged inside. A pole piece is arranged below the permanent magnet. A plunger is movably arranged below the pole piece. The plunger is a spring loaded plunger. A pick up coil and a hold on coil are wound concentrically in the coil bobbin arranged below the plunger. The pick
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up coil is a low resistance coil. The hold on coil is a high resistance coil. A coil power supply control circuit is connected to the incoming power supply, to the pick up coil and the hold on coil. The circuit disconnects the power supply to the pick up coil and maintains the power supply to the hold on coil, when the permanent magnet is latched with the plunger. The circuit includes electronic switches connected to the pick up coil. The electronic switches disconnect the power supply to the pick up coil, when the plunger is energized to move up to the permanent magnet to latch with permanent magnet.
E) BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:
[0015] FIG. 1 illustrates a sectional view of under-voltage release in circuit
breaker at hold-on position according to one embodiment of the present invention.
[0016] FIG. 2 illustrates a sectional view of under-voltage release in circuit
breaker at drop-off position according to one embodiment of the present invention.
[0017] FIG. 3 illustrates a block circuit diagram of coil power supply control
circuit in under voltage release according to one embodiment of the present invention.
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[0018] Although specific features of the present invention are shown in some
drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.
F) DETAILED DESCRIPTION OF THE INVENTION
[0019] In the following detailed description, reference is made to the
accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense.
[0020] The various embodiments of the present invention provide a simple
under-voltage release for air circuit breakers to reduce power loss due to excess power consumption, reduce heat generation. The under-voltage release delivers power proportionate to difference between magnet power and spring power, where the spring power is higher than holding force of the magnet.
[0021] According to one embodiment of the present invention, an under voltage
release system with low power consumption for circuit breaker has a magnetic frame housing in which a permanent magnet is arranged inside. A pole piece is arranged below the permanent magnet. A plunger is movably arranged below the pole piece.


The plunger is a spring loaded plunger. A pick up coil and a hold on coil are wound concentrically in the coil bobbin arranged below the plunger. The pick up coil is a low resistance coil. The hold on coil is a high resistance coil. A coil power supply control circuit is connected to the incoming power supply, to the pick up coil and the hold on coil. The coil power supply control circuit disconnects the power supply to the pick up coil and maintains the power supply to the hold on coil, when the permanent magnet is latched with the plunger. The circuit includes electronic switches connected to the pick up coil. The electronic switches disconnect the power supply to the pick up coil, when the plunger is energized to move up to the permanent magnet to latch with permanent magnet.
[0022] The under-voltage release for air circuit breakers includes a permanent
magnet, a pole-piece, a plunger, a coil around a core, a spring and a magnetic frame housing all components. The coil is connected to the power supply of the breaker circuit to magnetize the core and the plunger. The coil is wound in two parts one is a pick-up coil and another being a hold-on coil. Once the power is supplied to the coil, due to magnetization the plunger moves to the pole-piece. The power-supply to the pick-up coil is cut-off using electronic switches and the power supply is retained only at the hold-on coil. When the plunger moves to the pole-piece, the permanent magnet takes over to hold the plunger. Thus, the permanent magnet and the plunger come to the hold-on position. During the hold-on position the hold-on coil delivers power proportionate to the difference between the magnet power and the spring force, where the spring force is marginally higher than the holding force of the magnet.


[0023] During under voltage conditions when the voltage of the power supply
goes below the specified limit the hold-on coil gets de-energized. The force of attraction between the pole-piece and the plunger is less than the force of repulsion exerted by the spring. Further, the spring decompresses separating the plunger and the pole-piece. Thus, the plunger and the permanent magnet go back to the drop-off position. The return movement of the plunger is utilized to trip of the circuit breaker when the power supply voltage goes below the specified limit.
[0024] The under-voltage release which utilizes optimum power for operating
the electrical switching device. The utilization of optimum power eliminates the excess power loss and heat generation in the electrical switching device. Further, incorporation of design makes the electrical system sturdy. Furthermore, the invention can be extended as an electrical reset arrangement for resetting the air circuit breaker remotely.
[0025] FIG. 1 illustrates a diagrammatic representation of under-voltage release
of circuit breaker for hold-on position according to one embodiment of the present invention. With respect to FIG. 1, the electrical switching device comprises a permanent magnet 190, a copper tube 200, a pole-piece 180, a plunger 140 and a control circuit connected to the incoming power supply. The above components of the electrical switching device are housed in a magnetic frame 110. The control circuit includes a hold-on coil 170 and a pick-up coil 160. The pick-up coil 360 is a low resistance coil and the hold-on coil 170 is a high resistance coil. The pick-up coil 160 and the hold-on coil 170 is wound on same bobbin 120 and placed concentrically


around the pole-piece 180 and the plunger 140. The pick-up coil 160 and the hold-on coil 170 are connected to the power supply. Once the plunger 140 travels to the pole-piece 180 forming a close-magnet state, the permanent magnet 190 takes over the plunger 140. During the close-magnet state the pick-up coil is cut-off and the hold-on coil is retained maintaining the plunger 140 at latched position. During the latched position there exists a race between the force exerted by the spring and the voltage the hold-on coil as seen by the hold-on coil.
[0026] FIG. 2 illustrates a diagrammatic representation of under-voltage release
of circuit breaker for drop-off position according to one embodiment of the present invention. The electrical switching device comprises a permanent magnet 190, a copper tube 200. a pole-piece 180. a plunger 140 and a control circuit connected to the incoming power supply. The above components of the electrical switching device are housed in a magnetic frame 110. The control circuit includes a hold-on coil 170 and a pick-up coil 160. During under voltage conditions when the voltage of the power supply goes below the specified limit the hold-on coil 170 gets deenergized. The force of attraction between the pole-piece 180 and the plunger 140 is less than the force of repulsion exerted by the spring 100. The energy stored in the compressed spring 150 is dominant over the decreased force of attraction between the pole-piece 180 and the plunger 140. Further, the spring 100 decompresses separating the plunger 140 and the pole-piece 180. Thus, the plunger 140 and the permanent magnet 190 come to a drop-off position. The return movement of the plunger 140 is utilized to trip of the circuit breaker when the power supply voltage goes below the specified limit.


[0027] FIG. 3 illustrates a diagrammatic representation of circuit diagram
describing connections of pick-up coil and hold-on coil according to one embodiment of the present invention. With respect to FIG. 3, the control circuit 240 is connected to the incoming power supply 210. The control circuit includes a hold-on coil 170 and a pick-up coil 160. During the close-magnet state the pick-up coil 160 is cut-off and the hold-on coil 170 is retained. During under voltage conditions when the voltage of the power supply 210 goes below the specified limit the hold-on coil 170 gets de-energized causing tripping of the circuit breaker.
G) ADVANTAGES OF THE INVENTION
[0028] Thus the various embodiments of the present invention provide an
under-voltage release which utilizes optimum power for operating the electrical switching device. The utilization of optimum power eliminates the excess power loss and heat generation in the electrical switching device. Further incorporation of design makes the electrical system sturdy. Furthermore, the invention can be extended as an electrical reset arrangement for resetting the air circuit breaker remotely.
[0029] Although the invention is described with various specific embodiments,
it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims.
[0030] It is also to be understood that the following claims are intended to cover
all of the generic and specific features of the present invention described herein and
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all the statements of the scope of the invention which as a matter of language might be said to fall there between.
RAKESH PRABHU
Patent Agent
Date: March 30, 2009. Place: Bangalore.

CLAIMS
What is claimed is:
1. An under voltage release system with low power consumption for circuit breaker comprising: a magnetic frame housing; a permanent magnet arranged inside the housing; a pole piece arranged below the permanent magnet in the housing; a plunger movably arranged below the pole piece; a coil bobbin arranged below the plunger; a pick up coil wound in the coil bobbin; a hold on coil wound in the coil bobbin; and
a coil power supply control circuit connected to the incoming power supply and to the pick up coil and the hold on coil,
wherein the coil power supply control circuit disconnects the power supply to the pick up coil and maintains the power supply to the hold on coil, when the permanent magnet is latched with the plunger.
2. The system according to claim 1. wherein the pick up coil and the hold on coil are wound concentrically in the same coil bobbin.
3. The system according to claim 1, wherein the coil power supply control circuit includes electronic switches connected to the pick up coil.


4. The system according to claim 1, wherein the electronic switches disconnects the power supply to the pick up coil, when the plunger is energized to move up to the permanent magnet to latch with permanent magnet.
5. The system according to claim 1. wherein the plunger is a spring loaded plunger.
6. The system according to claim 1, wherein the pick up coil is a low resistance coil.
7. The system according to claim 1, wherein the hold on coil is a high resistance coil.

RAKESH PRABHU Patent Agent,
ALMT Legal,
#2, Lavelle Road, Bangalore-560 001
To,
The Controller of Patents, The Patent Office, Mumbai
Dated this the 30th day of March 2009