Claims:We Claim:
1. An operating mechanism (1) for restricting trip linkage lifting in withdrawable circuit breaker, the operating mechanism (1) comprising:
a main trip link assembly (4) having linkages including,
a main trip link (5) having a locking rivet (11) mounted thereon for increasing load bearing capacity of the withdrawable circuit breaker, the main trip link (5) further including a slot (15) with a concave profile configured thereon, the main trip link (5) being pivoted on a charging shaft (12), the charging shaft (12) adapted for charging the operating mechanism (1) using compression springs and a follower assembly (13) operatively connected thereto,
a driver link (6) pivotally mounted to the main trip link (5) using a pivot pin (16) mounted thereon, the driver link (6) including a locking profile (6a) with an outward projection (6b) configured at one end thereof for enabling removable engagement within the slot (15) during ON condition of the withdrawable circuit breaker, and
a coupler link (7) operably connected at one end to the driver link (6), the coupler link (7)including a poleshaft assembly (3) attached thereto at other end thereof;
wherein in response to switching ON the withdrawable circuit breaker in the spring discharged condition, the main trip link assembly (4) moves due to spring action enabling rotation of the poleshaft assembly (3) to cause movement of moving contacts (poles) connected thereto thereby facilitating closing operation of the withdrawable circuit breaker in response thereof, and
wherein in response to movement of the main trip link assembly (4), the driver link (6) rotates around the pivot pin (16) such that the locking profile (6a) of the driver link (6) operatively engages within the slot (15) whereas the outward projection (6b) of the driver link (6) rests on the locking rivet (11) of the main trip link (5), and thereinafter positioning an auxiliary trip link (10) resting on a trip D- shaft (9) onto the main trip link (5) results in latching of the operating mechanism (1) for restricting any further movement thereof, such that the driver link (6) resting on the locking rivet (11) creates a counter torque (T2) about the pivot pin (16) on the charging shaft (12) in response to a reaction torque (T1) generated from the moving contacts (14) during faulty condition to form a couple effect for restricting lifting of the main trip link assembly (4) and increasing load bearing capacity of the withdrawable circuit breaker thereby preventing immediate opening of the moving contacts (14) of the withdrawable circuit breaker resulting into damage thereof in response to a short circuit condition.

2. An operating mechanism (1) as claimed in claim 1, wherein the operating mechanism (1) is charged using the charging shaft (12) and the cam follower action of the follower assembly (13) of the withdrawable circuit breaker.

Dated this 30th day of March 2017

Prafulla Wange
(Agent for Applicant)
IN-PA/2058 , Description:OPERATING MECHANISM FOR RESTRICTING TRIP LINKAGE
LIFTING IN CIRCUIT BREAKERS

Field of the invention
The present invention relates to the field of switchgears and circuit breakers. More particularly the present invention relates to the operating mechanism for restricting trip linkage movement in circuit breakers.
Background of the invention
Circuit breakers are electrical devices that are installed in an electrical circuit to allow the connection and disconnection of the circuit from the power source. Circuit breaker are commonly known as interrupters that opens and closes to stop and start the flow of electrical current to the electrical circuit.
Circuit breakers are used to safeguard the electrical equipment from over current situations caused or short current situations in equipment. On flow of fault current conditions, the electrical contacts within the circuit breaker will open and it stops the flow of electrical current through the circuit breaker to the equipment. In case of fault generation, circuit breakers are expected to withstand fault current before opening the contacts.
The operating mechanism of a circuit breaker having a moving contact and a stationary contact is switched ON (closed) or OFF (tripped) by using energy stored in a compressed or stretched spring. When the circuit breaker is closed, energy is stored in the contact springs. This energy is locked with latching arrangement through a set of linkages. When the latching arrangement is de-latched by moving the linkages, the energy stored in the springs is released to trip the breaker.
When the circuit breaker is ON (closed) condition, the circuit is complete and current flows. The electrodynamic strength of the circuit breaker results from the action of the contact pressure springs on the multiple fingers of the poles and of the compensated contacts. While closing the breaker, a set of linkages of operating mechanism gets rotated due to the force transmitted by the compressed springs. Linkage movement rotates the Poleshaft connected to the moving contacts and thus the breaker is closed. The linkages get latched in order to prevent nuisance tripping of the breaker.
In existing breakers, the operating mechanism has a combination of links which drive the moving contacts for closing and opening the breaker. When high fault current is present a high mechanical reaction torque is being transferred on to the mechanism linkages, the toggle links gets lifted due to which the Poleshaft gets rotated leading to undesirable opening of contacts without withstanding the fault current leading to breaker failure.
Therefore, there exists a need to provide a modified operating mechanism for restricting the linkage movement in high fault current condition. There is a need to provide a modified operating mechanism which overcomes the above mentioned drawbacks of the existing systems.
Objects of the invention
The primary object of present invention is to prevent lifting of linkages during high fault conditions in withdrawable circuit breaker.
Another object of present invention is to increase the load bearing capacity of the linkages and thus restricting the linkage movement in high fault current conditions of the withdrawable circuit breaker.
Yet another object of present invention is to allow the withdrawable circuit breaker to withstand higher fault current by providing an operating mechanism for restricting the trip linkage movement in high fault occurrence.
Summary of the invention
The present invention provides an operating mechanism for restricting trip linkage lifting in withdrawable circuit breaker. The operating mechanism comprises of a main trip link assembly having linkages including a main trip link, a driver link and a coupler link. The main trip link is pivoted on a charging shaft. The main trip link includes a locking rivet and a slot with a concave profile configured thereon. The locking rivet is adapted for increasing load bearing capacity of the withdrawable circuit breaker. The charging shaft is adapted for charging the operating mechanism using compression springs and a follower assembly connected thereto. Particularly, the operating mechanism is charged using the charging shaft and cam profile action of the follower assembly. The driver link is pivotally mounted to the main trip link using a pivot pin. The driver link includes a locking profile with an outward projection configured at one end thereof for enabling removable engagement within the concave profile of the slot during ON condition of the withdrawable circuit breaker. Particularly, the locking profile engages/rests within the slot of the main trip link whereas the outward projection engages around the locking rivet of the main trip link during ON condition of the withdrawable circuit breaker. The coupler link is operably connected at one end to the driver link. The couple link includes a poleshaft assembly attached thereto at other end thereof.
When the withdrawable circuit breaker is switched ON, the main trip link assembly moves due to spring action thereby enabling rotation of the poleshaft assembly connected to the coupler link. Movement of the poleshaft assembly causes movement of moving contacts connected thereto thereby facilitating closing operation of the withdrawable circuit breaker. In ON condition of the withdrawable circuit breaker, upon movement of the main trip assembly, the driver link rotates around the pivot pin such that the locking profile of the driver link operatively engages with the slot whereas the outward projection rests on the locking rivet of the main trip link. The mechanism is latched in this condition by the auxiliary trip link resting on the Trip shaft. When the fault occurs, a high mechanical reaction torque (T1) is being transmitted on to the mechanical linkages. The driver link resting on the locking rivet creates a counter torque (T2) about the pivot pin on the charging shaft thus reducing the torque effect which leads to lifting of the main trip link assembly. Thus, as the counter torque (T2) is generated, a couple is created thus reducing the linkage lifting and thus preventing the opening of the moving contacts in fault condition without withstanding the fault and leading to the withdrawable circuit breaker failure.
Brief description of the drawings
Figure 1 shows an overview of Operating Mechanism of withdrawable circuit breaker, in accordance with the present invention;
Figure 2 shows an Operating Mechanism with Modified Main trip link assembly in main spring charged and withdrawable circuit breaker OFF Condition, in accordance with the present invention;
Figure 3 shows an Operating Mechanism with Modified Main trip link assembly in main spring discharged and withdrawable circuit breaker ON Condition, in accordance with the present invention;
Figure 4 shows a detailed view of the modified main trip link assembly in the withdrawable circuit breaker OFF Condition, in accordance with the present invention;
Figure 5 shows a detailed view of the modified main trip link assembly in the withdrawable circuit breaker ON Condition, in accordance with the present invention;
Detailed description of the invention
The foregoing objects of the invention are accomplished and the problems and shortcomings associated with the prior art techniques and approaches are overcome by the present invention as described below in the preferred embodiment.
The present invention provides an operating mechanism for restricting trip linkage lifting in withdrawable circuit breaker. The operating mechanism generates an equal opposing torque to minimize the torque effect leading to linkage lifting. The operating mechanism, in faulty condition, generates opposing counter torque (T2) thus reducing the linkage lifting and thus preventing the opening of the moving contacts in fault condition without withstanding the fault and leading to the withdrawable circuit breaker failure.
This present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description.
Referring to figures 1 to 5, disclosed is an operating mechanism (1), (hereinafter referred to as “the operating mechanism (1)”) for restricting trip linkage lifting in withdrawable circuit breaker.
Referring to figure 2, shown is the operating mechanism (1) of the withdrawable circuit breaker in charged OFF condition. The operating mechanism (1) comprises of a main trip link assembly (4) having linkages including a main trip link (5), a driver link (6) and a coupler link (7). The main trip link (5) is pivoted on a charging shaft (12). The main trip link (5) includes a locking rivet (11) and a slot (15) with a concave profile configured thereon. The locking rivet (11) is adapted for increasing load bearing capacity of the withdrawable circuit breaker for fault clearance. The charging shaft (12) is adapted for charging the operating mechanism (1) with the help of compression springs and a follower assembly (13) connected thereto. Particularly, the MTL assembly (4) is pivoted on the charging shaft (12). More particularly, the operating mechanism (1) is charged using the charging shaft (12) and cam profile action of the follower assembly (13). The driver link (6) is pivotally mounted to the main trip link (5) using a pivot pin (16). The driver link (6) includes a locking profile (6a) with an outward projection (6b) configured at one end thereof for enabling removable engagement within the concave profile of the slot (15) during ON condition of the withdrawable circuit breaker. Particularly, the locking profile (6a) engages within the slot (15) of the main trip link (5) whereas the outward projection (6b) engages around the locking rivet (11) of the main trip link (5) during ON condition of the withdrawable circuit breaker. The coupler link (7) is operably connected at one end to the driver link (6). The coupler link (7) includes a poleshaft assembly (3) attached thereto at other end thereof. The circuit breaker is in ready to close condition. The profile of the driver link (6) is modified for achieving higher load bearing capacity.
Referring to figure 3, shown is the operating mechanism (1) in spring discharged and the withdrawable circuit breaker ON condition. When the withdrawable circuit breaker is switched ON, the main trip link assembly (4) including the linkages move due to spring action thereby rotating the poleshaft assembly (3) connected to the coupler link (7). The poleshaft assembly (3) is further connected to the moving contacts (poles) (14). Thus, movement of the poleshaft assembly (3) causes movement of the moving contacts (14) connected thereto thus closing the withdrawable circuit breaker. In ON condition of the withdrawable circuit breaker, upon movement of the main trip link (MTL) assembly (4), the driver link (6) rotates about the pivot pin (16) and rests on the slot (15) provided on the main trip link (5). In an embodiment, the locking profile (6a) of the driver link (6) operatively engages/rests within the slot (15) whereas the outward projection (6b) rests on the locking rivet (11) of the main trip link (5). The mechanism is latched in this condition by an auxiliary trip link (10) resting on a trip D- shaft (9). When the fault occurs, a high mechanical reaction torque (T1) is being transmitted on to the mechanical linkages of the main trip link assembly (4). The driver link (6) resting on the locking rivet (11) creates a counter torque (T2) about the MTL pivot pin (16) on the charging shaft (12) thus reducing the torque effect which leads to lifting of the main trip link assembly (4).
Referring to figure 4, shown is detailed view of the main trip link assembly (4) in OFF condition of the withdrawable circuit breaker with the main trip link (5), the driver link (6), and the locking rivet (11).As can be seen in figure 4, the driver link (6) is with changed profile. The driver link (6) is pivoted with the main trip link (5) and the coupler link (7). The locking rivet (11) is mounted on the main trip link (5).
Referring to figure 5, shown is detailed view of the main trip link assembly (4) in ON condition of the withdrawable circuit breaker with the main trip link (5), the driver link (6), and the locking rivet (11). The driver link (6) rests on the slot (15) on the main trip link (5) with one end resting on the locking rivet (11). Figure 5 also shows the Couple created due to the reaction torque (T1) from the poles (14) and the counter Torque (T2) by the locking rivet (11). As the counter torque (T2) is generated, a couple is created thus reducing the linkage lifting and thus preventing the opening of the moving contacts (14) in fault condition without withstanding the fault and leading to the withdrawable circuit breaker failure. Thus, an improved and efficient performance of the operating mechanism (1) of withdrawable circuit breaker is being achieved.
Thus, the present invention provides the operating mechanism (1) with modified main trip linkages for increasing the load bearing capacity and thus restricting the linkage movement in high fault current condition. The modified profile of the driver link (6) rests on the locking rivet (11) mounted on the main trip link (5) when the withdrawable circuit breaker is in ON condition. In case of fault generation, due to the modified profile resting on the locking rivet (11), a counter torque is being generated creating a couple and thus reducing the torque effect and preventing the lifting of the trip linkages and allowing the withdrawable circuit breaker to clear the fault.
Advantages of the present invention
1. The present invention provides efficient and improved Operating mechanism (1) with increased load bearing capacity.
2. Arrangement of the Main Trip Link (MTL) Assembly (4) with modified profile helps in increased load bearing capacity.
3. Locking rivet (11) Arrangement helps in counter torque generation.
4. Lifting of Linkages prevented.
5. The present invention provides the withdrawable circuit breaker with efficient operating mechanism (1) for clearing high fault current.
6. The present invention providing sufficient counter torque for restricting the lifting of mechanism linkages in case of fault occurrence.
7. Clearance of fault with withstanding higher current.
8. Restriction of the Poleshaft assembly (3) movement.
9. Contact opening prevention in case of withstanding fault current.

The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiment. Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system (100), structure, or matter. The embodiments of the invention as described above and the methods disclosed herein will suggest further modification and alterations to those skilled in the art. Such further modifications and alterations may be made without departing from the spirit and scope of the invention.