A) TECHNICAL FIELD

[0001] The present invention generally relates to switchgear applications and particularly to remote operation of Moulded Case Circuit Breaker (MCCB). The present invention more particularly relates to an electrical operating mechanism for MCCB using solenoid principle.

B) BACKGROUND OF THE INVENTION

[0002] The circuit interrupters are widely used in domestic, commercial and light industrial installations to protect electrical circuits from overload and short circuit faults. In current technology, either a motor operator or solenoid operator is used for the remote electrical operation of the circuit breaker. The size of the Electrical Operating Mechanism (EOM) is large due to coil accommodations. The Motor operator is preferred in current technologies due to less power required for the operation of the motor operated EOM compared to the solenoid operated EOM.

[0003] However, in the current technology, the power consumed by the EOM is high and the size of the coil required for a long stroke operation of the EOM is big. Further, a separate power source is required in case of high power consumption by the EOM. Moreover, the leakage flux produced during a long stroke of operation of the EOM is higher which in turn necessitates an increase in the size of the coil.

[0004] In the Long Stroke Solenoid operations, the leakage flux produced is higher and the EOM requires more amount of power for the operation. During normal Solenoid operation, there exists a residual flux even after the de-energisation of the first coil. The presence of the residual flux plays major role while energising the second coil and hence the starting force of the plunger is reduced. Moreover, the force produced by the solenoid at the end of the long stroke is high during the normal Solenoid operation.

[0005] Hence, there exists a need to provide an efficient EOM for circuit breakers to reduce the leakage flux to improve the performance of the solenoid coil. Further, there is a need to reduce the coil size of the solenoid and overall size of the EOM. Also there is a need to reduce the force produced by the solenoid coil at the end of the stroke operation of the EOM.

[0006] The above mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and sstudying the following specification.
C) OBJECT OF THE INVENTION

[0007] The primary object of the present invention is to provide an EOM for circuit breakers to reduce the leakage flux for improving the performance of the solenoid coil.

[0008] Another object of the present invention is to provide an EOM for circuit breakers to reduce the coil size of the solenoid.

[0009] Another object of the present invention is to provide an EOM for circuit breakers to reduce the force produced by the solenoid coil at the end of the stroke operation of the EOM.

[0010] Yet another object of the present invention is to provide an EOM for circuit breakers for long stroke operation using a single plunger.

[0011] Yet another object of the present invention is to provide an EOM for circuit breakers to avoid the use of separate power source for EOM.

[0012] These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjvmction with the accompanying drawings.

D) SUMMARY OF THE INVENTION

[0013] The various embodiments of the present invention provide an EOM for circuit breakers to reduce the flux leakage and improve performance of the solenoid coil. The EOM
includes a stationary core, a first bracket, a second bracket fixed on two sides of housing of the stationary core and at least two non magnetic rods fixed to the stationary core which are provided between the first bracket and a second bracket. The EOM also includes a moving plunger coupled to the two non magnetic rods which is movable between the first bracket and the second bracket. Further, the EOM includes a first solenoid coil mounted on the first bracket and a second solenoid coil mounted on the second bracket. The first bracket and the second bracket reduce the leakage flux induced in the EOM by reducing the air gap between the moving plunger and the stationary core at the start of a stroke operation of the EOM.

[0014] According to one embodiment of the present invention, the first bracket and the second bracket are rectangular in shape. The first solenoid coil and the second solenoid coil are formed by winding a copper coil on a non magnetic nylon coil former. The first solenoid coil is energized during the switching ON operation of the circuit breaker. The second solenoid coil is energized during the switching OFF operation of the circuit breaker. The moving plunger is forced to move towards the second bracket due to an axial flux flow between the moving plunger and the second bracket, during the energizing of the second solenoid coil for OFF operation of the circuit breaker. Further, the moving plunger is forced to enter the second bracket due to a radial flux flow between the moving plunger and the second bracket and forms a small air gap between the moving plunger
and the stationary core, during the energizing of the second solenoid coil for switching OFF the circuit breaker.

[0015] According to one embodiment of the present invention, one end of the moving plunger is fixed with a circuit breaker knob connector to connect with a knob of the circuit breaker. The circuit breaker knob connector is provided with a slot to receive the knob of the circuit breaker. The non magnetic rods are made of brass. The moving plunger, the first bracket, the second bracket and the circuit breaker knob connector is made of mild steel. The EOM reduces the flux leakage and improves performance of the solenoid coil. The EOM reduces the coil size of the solenoid and overall size of the EOM. The EOM reduces the force produced by the solenoid coil at the end of the stroke operation of the EOM. The EOM reduces power rating (VA) of the solenoid coil and thereby prevents use of a separate power source for the EOM. The solenoid coils and the stationary core of the EOM provides low reluctance flux path in the EOM.

E) BRIEF DESCRIPTION OF THE DRAWINGS

[0016] 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:

[0017] FIG. 1 illustrates a top perspective view of an Electrical Operating Mechanism (EOM) according to one embodiment of the present invention.

[0018] FIG.2 illustrates a perspective view of the brackets and moving plunger assembly of the EOM according to one embodiment of the present invention.

[0019] FIG. 3 illustrates a sectional view of the Electrical Operating Mechanism (EOM) according to one embodiment of the present invention.

[0020] FIG. 4 illustrates a sectional view of the Electrical Operating Mechanism (EOM) showing axial flux flow in the circuit breaker according to one embodiment of the present invention.

[0021] FIG. 5 illustrates a sectional view of the Electrical Operating Mechanism (EOM) showing axial flux flow and radial flux flow in the circuit breaker according to one embodiment of the present invention.

[0022[ FIG. 6 illustrates a sectional view of the Electrical Operating Mechanism (EOM) showing direction of flow of axial flux, radial flux and total flux flow in the circuit breaker according to one embodiment of the present invention.

[0023] FIG. 7 illustrates a front view showing the arrangement of Moulded case Circuit Breaker (MCCB) on the EOM assembly according to one embodiment of the present invention.

[0024] 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

[0025] 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.

[0026] The various embodiments of the present invention provide an EOM for Moulded case circuit breakers (MCCB) to reduce the leakage flux and improve performance of the solenoid coil. The EOM includes a stationary core, a first bracket and a second bracket fixed on two sides of the housing of the stationary core and at least two non magnetic rods fixed to the stationary core which are provided between the first bracket and a second bracket. The EOM also includes a moving plunger coupled to the at least two non magnetic rods. The moving plunger is movable between the first bracket and the second bracket. Further, the EOM includes a first solenoid coil mounted on the first bracket and a second solenoid coil mounted on the second bracket. The first bracket and the second bracket reduce the leakage flux induced in the EOM by reducing air gap between the moving plimger and the stationary core at the start of a stroke operation of the EOM.

[0027] According to one embodiment of the present invention, the first bracket and the second bracket are rectangular in shape. The first solenoid coil and the second solenoid coil are formed by winding a copper coil on a non magnetic nylon coil former. The first solenoid coil is energized during the switching ON operation of the circuit breaker. The second solenoid coil is energized during the switching OFF operation of the circuit breaker. The moving plunger is forced to move towards the second bracket due to an axial fiux flow between the moving plunger and the second bracket, during the energisation of the second solenoid coil for OFF operation of the circuit breaker. Further, the moving plunger is forced to enter the second bracket due to a radial flux flow between the moving plunger and the second bracket. The movement creates a narrow air gap between the moving plunger and the stationary core, during energizing the second solenoid coil for the switching OFF operation of the circuit breaker.

[0028] According to one embodiment of the present invention, one end of the moving plunger is provided with a circuit breaker knob cormector to connect with a knob of the circuit breaker. The circuit breaker knob connector is provided with a slot to receive the knob of the circuit breaker. The non magnetic rods are made of brass. The moving plunger, the first bracket, the second bracket and the circuit breaker knob connector are preferably made of mild steel.

[0029] FIG. 1 illustrates a top side perspective view of the Electrical Operating Mechanism (EOM) according to one embodiment of the present invention. With respect to FIG. 1, the EOM includes a stationary core 101. The EOM assembly further includes a first bracket 102a and a second bracket 102b fixed on two sides of the housing of the stationary core 101 and two non-magnetic rods fixed to the stationary core 101 which are provided between the first bracket 102a and a second bracket 102b (as shown in FIG.2). The EOM also includes a moving plunger 104 coupled to the two non magnetic rods 103 which is movable between the first bracket 102a and the second bracket 102b. Further, the EOM includes a first solenoid coil 105a mounted on the first bracket 102a and a second solenoid coil 105b mounted on the second bracket 102b. One end of the moving plunger 104 is provided with a circuit breaker knob connector 106 to connect with a corresponding knob of the circuit breaker. The moving plunger 104 and the circuit breaker knob connector 106 are made of mild steel. The first solenoid coil 105a and the second solenoid coil 105b are formed by winding a copper coil on a non magnetic nylon coil former. The first solenoid coil 105a is energized during ON operation of the circuit breaker. The second solenoid coil 105b is energized during OFF operation of the circuit breaker.

[0030] FIG.2 illustrates an isometric view of the brackets 102a, 102b and moving plunger 104 assembly of the EOM according to one embodiment of the present invention. With respect to FIG. 2, a first bracket 102a and a second bracket 102b are fixed on the two sides of the housing of the stationary core 101. Two non magnetic rods 103 are fixed to the stationary core 101 which are provided between the first bracket 102a and the second bracket 102b. At least one end of the two non-magnetic rods is coupled to the moving plunger 104. The moving plunger 104 is adapted to move between the first bracket 102a and the second bracket 102b. The circuit breaker knob connector 106 is provided with a slot to receive the knob of the circuit breaker. The non magnetic rods 103 are made of brass. The moving plunger 104, the first bracket 102a, the second bracket 102b and the circuit breaker knob connector 106 is made of mild steel.

[0031] FIG. 3 illustrates a sectional view of the Electrical Operating Mechanism (EOM) according to one embodiment of the present invention. The EOM includes a stationary core 101. A first bracket 102a and a second bracket 102b are fixed on two sides of housing of the stationary core 101 and two non magnetic rods 103 are fixed to the stationary core 101 which are provided between the first bracket 102a and a second bracket 102b. The EOM also includes a moving plunger 104 coupled to the two non magnetic rods 103 which is movable between the first bracket 102a and the second bracket 102b. Further, the EOM includes a first solenoid coil 105a mounted on the first bracket 102a and a second solenoid coil 105b mounted on the second bracket 102b. The non magnetic rods 103 are made of brass. The moving plunger 104, the first bracket 102a, the second bracket 102b and the circuit breaker knob cormector 106 is made of mild steel. The first solenoid coil 105a and the second solenoid coil 105b is formed by winding copper coil on a non magnetic nylon coil former. The first solenoid coil 105a is energized during the switching ON of the circuit breaker. The second solenoid coil 105b is energized during the switching OFF operation of the circuit breaker.

[0032] FIG. 4 illustrates a sectional view of the Electrical Operating Mechanism (EOM) showing an axial flux flow in the circuit breaker according to one embodiment of the present invention, The axial flux flow is directed along the axis of with respect to the central stationary core of the EOM during a OFF operation of circuit breaker according to one embodiment of the present invention. With respect to FIG. 4, at an initial stage, the moving plunger 104 is moved towards the first solenoid coil 105a within the first bracket 102a indicating an ON operation of the circuit breaker. During a fault condition, the second solenoid coil 105b is energized. Further, considering a long stroke operation of the EOM, the movement of the moving plunger 104 is divided into two halves. During the first half stroke of operation, the moving plunger 104 is forced to move towards the second bracket 102b due to an axial flux flow induced between the moving plunger 104 and the second bracket. The direction of flow of the axial flux is as indicated by the arrow shown in the FIG. 4.

[0033] FIG. 5 illustrates a sectional view of the Electrical Operating Mechanism (EOM) indicating an axial flux flow and radial flux flow in the circuit breaker according to one embodiment of the present invention. The energizing of the second solenoid coil 105b during the switching OFF operation of the circuit breaker initiates the axial flux flow and the radial flux flow through the circuit breaker.

[0034] With respect to FIG. 5, the moving plunger 104 is shifted towards the second solenoid coil 105b within the second bracket 102b indicating the switching OFF the circuit breaker. During fault condition, the second solenoid coil 105b is energized. Further, the movement of the moving plunger 104 is divided into two halves during a long stroke operation of the EOM. During the first half stroke of operation, the moving plunger 104 is forced to move towards the second bracket 102b due to an axial flux flow induced between the moving plunger 104 and the second bracket 102b. The direction of flow of the axial flux is as shown in the FIG. 4 and FIG 5. In second half stroke of operation, the moving plunger 104 is forced to enter the second bracket 102b due to a radial flux flow between the moving plunger 104 and the second bracket 102b. This movement creates a small air gap between the moving plunger 104 and the stationary core 101. The direction of flow of the radial flux is as indicated by the directional arrows shown in the FIG. 5. The moving plunger 104 on entering into the second bracket 102b, a minimal uniform air gap between the moving plunger 104 and the second bracket 102b is maintained with help of the non-magnetic rods 103. The moving Plunger 104 does not come in contact with the second bracket 102b and hence a reduced radial air gap is maintained throughout the long stroke operation of the EOM. Due to reduced air gap, the leakage flux within the EOM is reduced. Moreover, due to the reduction of the air gap, the ampere turns required for the operation of the solenoid coils is reduced. Furthermore, the size of the EOM and power (VA) required for operation of the EOM is reduced.

[0035] FIG. 6 illustrates a sectional view of the Electrical Operating Mechanism (EOM) indicating the direction of flow of axial flux, radial flux and total flux flow while energizing second solenoid coil for OFF operation of circuit breaker according to one embodiment of the present invention. With respect to FIG. 6, the moving plunger 104 is moved towards the second solenoid coil 105b. The movement of the moving plunger 104 towards the second bracket 102b while energizing the second solenoid coil 105b for OFF operation of the circuit breaker is as illustrated in FIG. 4 and FIG. 5. Long stroke operation of the EOM is complete through flow of the axial flux 401 and the radial flux 501 within the EOM. The direction of flow of the axial flux is as indicated by the arrow 401, the arrow 501 indicates the radial flux flow and the arrow 601 indicates the flow of the total flux.

[0036] FIG. 7 illustrates a front view of the EOM assembly showing an arrangement of the circuit breaker knob according to one embodiment of the present invention. With respect to FIG.7, the knob of circuit breaker is connected to Moulded Case Circuit B reaker (MCCB) knob cormector 106 of an EOM assembly. With respect to FIG.7, the EOM 701 is connected to the MCCB 702 through the MCCB knob connector 106. The MCCB knob cormector 106 is provided with a slot to receive the knob 703 of the MCCB. The knob 703 of the MCCB is fixed into the slot of the MCCB knob connector 106 to make or break the MCCB 702 by energizing one of solenoid coils provided in the EOM 701. The MCCB knob connector in turn is fixed to the plunger as shown in FIG. 7.
The MCCB knob and MCCB knob connector are connected such that the MCCB knob is moving inside the slot provided in the MCCB knob connector.
G)

ADVANTAGES OF THE INVENTION

[0037] The various embodiments of the invention provide an Electrical Operating Mechanism (EOM) for circuit breakers. The EOM reduces the leakage flux and improves the performance of the solenoid coil. The EOM reduces the coil size of the solenoid and overall size of the EOM. The EOM reduces the force produced by the solenoid coil at the end of the stroke operation of the EOM. The EOM reduces power rating (VA) of the solenoid coil and thereby prevents the use of a separate power source for the EOM. The solenoid coils and the stationary core of the EOM provides low reluctance flux path in the EOM.
[0038] 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.
[0039] 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 all the statements of the scope of the invention which as a matter of language might be said to fall there between.

CLAIMS

What is claimed is:
1.An electrical operating mechanism (EOM) for circuit breakers, the mechanism comprising:

a stationary core;

a first bracket arranged on a housing of the stationary core;

a second bracket arranged opposite to the first bracket in the housing;

at least two non magnetic rods provided between the first bracket and the second bracket;

a moving plunger coupled to the at least two non magnetic rods;

a first solenoid coil mounted on the first bracket; and

a second solenoid coil mounted on the second bracket;

Wherein the first bracket and the second bracket reduces leakage flux by reducing an air gap between the moving plunger and the stationary core at an
start of a stroke operation.

2. The EOM of claim 1, wherein the first bracket and the second bracket are rectangular in shape.

3. The EOM of claim 1, wherein the first solenoid coil is energized during ON operation of the circuit breaker.

4. The EOM of claim 1, wherein the second solenoid coil is energized during OFF operation of the circuit breaker.

5. The EOM of claim 1, wherein the moving plunger is arranged so as to drift between the first bracket and the second bracket.

6. The EOM of claim 1, wherein an axial flux flow between the moving plunger and the second bracket drifts the moving plunger towards the second bracket during an energisation of the second solenoid coil for OFF operation of the circuit breaker.

7. The EOM of claim 1, wherein a radial flux flow between the moving plunger and the second bracket forces the moving plunger to be in contact with the second bracket thereby creating an air gap between the moving plunger and the stationary core.

8. The EOM of claim 1, wherein one end of the moving plunger is fixed with a circuit breaker knob connector to connect with a knob of the circuit breaker.

9. The EOM of claim 9, wherein the circuit breaker knob connector is provided with a slot to receive the knob of the circuit breaker.

10. The EOM of claim 10, wherein the circuit breaker knob and the circuit breaker knob connector are connected such that the circuit breaker knob moves inside the slot of the circuit breaker knob connector.

11. The EOM of claim 1, wherein the non magnetic rods are made of brass.