F O R M 2

THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)

1. Title of the invention: AN IMPROVED WIDE BAND SHUNT RELEASE ASSEMBLY FOR USE IN CIRCUIT BREAKERS

2. Applicant(s):

(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY : An Indian Company
(c) ADDRESS : L & T House, Ballard Estate, Mumbai 400 001,
State of Maharashtra, India

3. PREAMBLE TO THE DESCRIPTION

The following specification particularly describes the invention and the manner in which it is to be performed:


FIELD OF THE NVENTION

The present invention relates to a shunt release assembly. More particularly, the invention is concerned about an improved wide band shunt release assembly for use in circuit breakers.

BACKGROUND OF THE INVENTION

An electrical switching device may be defined as a unit designed to connect, carry and disconnect electrical supply. An electrical circuit breaker may be defined as a unit designed to connect, carry, disconnect and protect the equipments connected in the electrical circuit from damage caused by overload, undervoltage or short circuit etc. A circuit breaker is a commonly used electrical switching device. A circuit breaker may have the protection devices either built-in or optional which may be selectively added or replaced later. The protection devices may provide protection against under voltage, over voltage, over current, earth fault, short circuit etc. Apart from protection device the circuit breaker may also be equipped with accessories meant for remote operation and electrical interlocking with other circuit breaker. The example of remote operation and electrical interlocking may be shunt release, closing release etc. The under voltage release provides protection against under voltage by disconnecting the supply when under voltage (below specified limit) or power failure occurs. The shunt and closing releases may be used for remotely opening and closing the circuit breaker contacts respectively.

The under-voltage releases are generally electromagnet connected to the in-coming supply of the circuit breaker. Under healthy supply condition the electro magnet remains closed. In case the power supply falls below 70% of the rated voltage (including power failure), the electro-magnet drops off. This drop off movement of the electro magnet may be utilized for switching OFF (tripping) the breaker.

Incase Under voltage protection is not provided in the system (Circuit Breaker) & if available supply is in the range of 70 - 110% of rated voltage, then standard Shunt Release can be used to switch off (tripping) the breaker. But if available supply voltage falls below 70% of rated voltage, it is not possible to switch off the breaker with the standard shunt release. The condition became more worsened if the breaker is installed in remote area.

The Wide Band Shunt Release comprises of a DC power operated electromagnet system. This system has a fixed-magnet, a movable magnet and a coil around the two magnets which operates on D.C. power. When DC power passes through the coil, it develops electro magnetic field. In presence of the electro magnetic field, the movable magnet moves towards the fixed magnet to establish contact with the fixed magnet. This is refereed as closed magnet position.

The coil draws large amount of power to close the magnets from open position (open magnet position is one in which the magnets are apart). Once the magnets reach closed magnet position the power required to hold the magnets together is much lower. However, the large amount of power drawn by the coil remains unchanged, unless it is controlled by some other means/ device associated with the electromagnet. This excess power drawn by the coil is a loss. Further, this excess power generates lot of heat and problems related to elevated temperature. (The movable magnet moving from open magnet position to close magnet position is called pick-up of the magnet, movable magnet moving from close magnet position to open magnet position is called drop off / reset position).

US patent document 6265957 discloses an electromagnet for shunt release and closing release. The document discloses a system comprising dual coil, dual spring, a pick up circuit, a hold on circuit and electronic circuit used to change over from pick up circuit to the hold on circuit. The pick up circuit may be used for closing the electro-magnet. Once the magnets are closed, the electronics may change over from 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 in this case still consumes considerable power to over come the spring force employed to store the energy required to trip the breaker (particularly if considerable safety margin is to be maintained and/or high trip-force is to be obtained). The system typically employs continuous monitoring of the supply and giving a drop-off command when the supply voltage drops below a pre-determined value acceptable by the standards and customers.

An Adjustable Trip Solenoid (US 2004/6724286) provides the adjustable air gap where the mechanical biasing force of the solenoid is either decreased or increased as the air gap increased or decreased.

Thus, there is a need to overcome the problems in the prior art. there is a need to have a simple and improved shunt release that can deliver higher force and still consume negligible (zero during drop off) power, generate less heat for applications that demand working in high ambient to enhance reliability and higher life of the protection device and associated/ neighboring equipments. There is a need of Wide Band Shunt Release which can trip (Off) the breaker even if the supply voltage falls below 70% of rated voltage. Therefore, present inventors have developed an improved wide band shunt release assembly for use in circuit breakers to reduce power loss and subsequent heat generation so as to increase reliability thereby enhancing the life of an electrical switching device.

OBJECTS OF THE INVENTION

An object of the present invention is to overcome the problems/disadvantages of the prior art.

Another object of the present invention is to provide an improved wide band shunt release assembly for use in circuit breakers

These and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided an improved wide band shunt release assembly for use in circuit breakers, said assembly comprising:
a housing;
a fixed magnet means;
a movable magnet means;
spring means;
a plunger means being operatively mounted on said movable magnet means;
a coil means;
wherein said coil means being operatively connected to an auxiliary contact means;
wherein said auxiliary contact means being operatively mounted on said circuit breaker;
wherein said plunger means being transmitted force to said breaker for tripping during pick up of said magnet means;
wherein said spring means adapted to provide the movable magnet means for resetting to its original position.

DETAILED DESCRIPTION OF THE INVENTION

According to the embodiment of the present invention there is provided an improved wide band shunt voltage release for the air circuit breaker comprises of a fixed magnet, movable magnet, ring, plunger, a coil around the core, a spring and a magnetic frame housing them all. The coil is connected to the normally contact of auxiliary contact. Under healthy condition, the breaker is in on condition & the normally open contact closes from the actuator that is coupled with the shaft of mechanism. At the time of switch off the breaker for maintenance purposes or under severe circumstances (If fault occurs the supply voltage falls to as low as 10-30% of rated voltage), provided available supply to shunt release. In uncontrolled condition the supply voltage can go up to as high as 130% of rated voltage. In either case the shunt release gets energizes & transmits force to the mechanism. Now the breaker gets switched off (tripped) & auxiliary contact comes back to its original position (normally open). Hence the supply gets cut off across shunt release & the return spring drives the movable magnet to its original position. As the shunt release can be operated in a wide range (10% to 130% of rated voltage). Hence it is called “wide band shunt release”.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Other features as well as the advantages of the invention will be clear from the following description.
In the appended drawings:

Figure 1(A) shows the diagrammatic representation of the wide band shunt release for the electrical switching device for drop off position.

Figure 1(B) shows the diagrammatic representation of the wide band shunt release for the electrical switching device for pick up position.

Figure 2 shows the circuit diagram describing the connections of the coil and the auxiliary contact.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and illustrate the best mode presently contemplated for carrying out the invention. Further functioning of the assembly has been discussed below to describe the way the assembly operates. However, such description should not be considered as any limitation of scope of the present unit. The structure thus conceived is susceptible of numerous modifications and variations, all the details may furthermore be replaced with elements having technical equivalence. In practice the materials and dimensions may be any according to the requirements, which will still be comprised within its true spirit.

According to a preferred embodiment of the invention, there is proved an improved wide band shunt release assembly for use in circuit breakers. The wide band shunt release assembly for the electrical switching device comprises a C-Bracket (120), C-Bracket cover (110), Former (130), Fixed magnet (140), plunger (150), Coil (170), Ring (190) and PCB (200) connected to the incoming power supply (210) as shown in figures 1a and 1b. The coil (170) of wide band shunt release is connected NO contact of auxiliary contact (220) as shown in figure 2. The auxiliary contact is mounted in the suitable position on circuit breaker such that when the breaker gets charged and ON, the NO of auxiliary contact closes. At the time of trip (off) the breaker, provided the available voltage and magnetic field is produced and hence the release gets picked up. This is shown in figure 1(b). In this condition the movable magnet (180) comes in contact with the fixed magnet (140). During Pick up the plunger (150) mounted on movable magnet (180) transmits the force to breaker and hence the breaker gets off (trip). Under this condition the NO of auxiliary contact opens again and it cuts off the available supply of release. Now the compression spring (160) helps the movable magnet (180) to reset to its original position. In the present invention, maintained the air gap constant and hence the force is varying the varying the input voltage supply. Wide band shunt release for an electrical switching can be operated as low as from 10% of rated voltage to 130% of rated voltage.

In addition to that a ring (190) is used for improving the magnetic efficiency of the system. The introduction of ring (190) helps us a lot in improving the magnetic circuit which further helps us in reducing the VA burden. The invention provides wide band shunt release that utilizes optimum power for operating the electrical switching device and eliminates the excess power loss and heat generation. Therefore, the invention enhances the performance and life of the electrical switching device. The incorporated design makes the system sturdy. The invention may also be extended for use as wide band closing and other volt metric releases.

Working Example:

Lab testing of the present invention shows that the wide band shunt release can trip the breaker from as low as 8% of rated voltage to 140% of rated voltage.

ADVANTAGES OF THE INVENTION

1. Trip the breaker as low as from 10% to 130%v of rated voltage remotely.
2. Eliminates the excess power loss

WE CLAIM:

1. An improved wide band shunt release assembly for use in circuit breakers, said assembly comprising:
a housing;
a fixed magnet means;
a movable magnet means;
spring means;
a plunger means being operatively mounted on said movable magnet means;
a coil means;
wherein said coil means being operatively connected to an auxiliary contact means;
wherein said auxiliary contact means being operatively mounted on said circuit breaker;
wherein said plunger means being transmitted force to said breaker for tripping during pick up of said magnet means;
wherein said spring means adapted to provide the movable magnet means for resetting to its original position.

2. Assembly as claimed in claim 1 further comprising a ring means.

3. Assembly as claimed in claim1 or 2, wherein said ring means adapted to reducing VA burden.

4. Assembly as claimed in claim 1, wherein said coil means being operatively connected to NO contact of said auxiliary contact means.

5. Assembly as claimed in claim 1, wherein said spring means is compression spring and the like.

6. Assembly as claimed in claim 1 further comprising a C-bracket means.

7. Assembly as claimed in claim 1 further comprising a C-bracket cover means.

8. Assembly as claimed in claim 1 further comprising a former means.

9. Assembly as claimed in claim 1 further comprising a PCB means.

10. Assembly as claimed in claim 1 wherein said assembly being adapted to operate in the range of about 8 % to 140% of rated voltage.

11. Assembly as claimed in claim 1 wherein said assembly being adapted to operate preferably in the range of about 10 % to 130% of rated voltage.

12. Assembly as claimed in claim 1 wherein said plunger means is spring loaded.

13. Assembly as claimed in any of the preceding claims adapted to consume almost zero power under normal condition.

14. An improved wide band shunt release assembly for use in circuit breakers as herein substantially described and illustrated with the accompanying drawings.