1. Field
The disclosed concept relates generally to electrical switching apparatus and, more particularly, to electrical switching apparatus, such as circuit breakers. The disclosed concept also relates to secondary trip mechanisms.
2. Background Information
Electrical switching apparatus, such as circuit breakers, provide protection for electrical systems from electrical fault conditions such as, for example, current overloads, short circuits, abnormal voltage and other fault conditions. Typically, circuit breakers include an operating mechanism, which opens electrical contact assemblies to interrupt the flow of current through the conductors of an electrical system in response to such fault conditions as detected, for example, by a trip unit. The electrical contact assemblies include stationary electrical contacts and corresponding movable electrical contacts that are separable from the stationary electrical contacts.
Among other components, the operating mechanisms of some low and medium voltage circuit breakers, for example, typically include a poleshaft, a trip actuator assembly, a closing assembly and an opening assembly. The trip actuator assembly responds to the trip unit and actuates the operating mechanism. The closing assembly and the opening assembly may have some common elements, which are structured to move the movable electrical contacts between a first, open position, wherein the movable and stationary electrical contacts are separated, and a second, closed position, wherein the movable and stationary electrical contacts are electrically connected. Specifically, the movable electrical contacts are coupled to the poleshaft. Elements of both the closing assembly and the opening assembly, which are also pivotably coupled to the poleshaft, pivot the poleshaft in order to effectuate the closing and opening of the electrical contacts.
It is important to that sufficient tripping force is provided to ensure the circuit breaker does, in fact, trip in response to a trip condition.
There is, therefore, room for improvement in electrical switching apparatus, such as circuit breakers, and in secondary trip mechanisms therefor.
These needs and others are met by embodiments of the disclosed concept, which are directed to a secondary trip mechanism for an electrical switching apparatus, such as a circuit breaker. Among other benefits, the secondary trip mechanism cooperates with the poleshaft to ensure the electrical switching apparatus properly trips in response to a trip condition.
As one aspect of the disclosed concept, a secondary trip mechanism is provided for an electrical switching apparatus. The electrical switching apparatus includes a housing, separable contacts enclosed by the housing, and an operating mechanism for opening and closing the separable contacts. The operating mechanism comprises a poleshaft, a latch assembly, and a trip D-shaft structured to unlatch the latch assembly in response to a trip condition. The secondary trip mechanism comprises: a trip D-shaft assembly structured to be disposed on the trip D-shaft; and a link assembly comprising a linking member, the linking member including a first end and second end disposed opposite and distal from the first end, the first end being structured to cooperate with the poleshaft, the second end cooperating with the trip D-shaft assembly. When the poleshaft moves in response to a trip condition, the linking member is structured to transmit movement of the poleshaft into movement of the trip D-shaft assembly.
The trip D-shaft assembly may include a hub having a recess, wherein the second end of the linking member cooperates with the shaft hub at or about the recess. The poleshaft may include an interlock pin, and the first end of the linking member may include a barb. The barb may be structured to interlock with the interlock pin. When the barb interlocks with the interlock pin, the linking member may be structured to move with the poleshaft.
The link assembly may further comprise a biasing element including a first end and a second end disposed opposite and distal from the first end of the biasing element. The first end of the biasing element may structured to be coupled to the housing of the electrical switching apparatus and the second end of the biasing element may be coupled to the linking member to bias the linking member into engagement with the poleshaft.
The housing of the electrical switching apparatus may further include a side plate assembly comprising a side plate. The side plate assembly may further comprise a cam action pin, wherein the cam action pin extends laterally outwardly from the side plate toward the linking member. The linking member may further comprise a cam surface, wherein the cam action pin is structured to cooperate with the cam surface to move the second end of the linking member into and out of engagement with the D-shaft.
An electrical switching apparatus including the aforementioned secondary trip mechanism is also disclosed.
A full understanding of the disclosed concept can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:
Directional phrases used herein, such as, for example, clockwise, counterclockwise, left, right, upward, downward and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein.
As employed herein, the phrase “toe touch position” refers to a position of an electrical switching apparatus (e.g., without limitation, circuit breaker) corresponding to an arcing contact portion (commonly referred to in the art as a “toe”) of a movable contact of the circuit breaker engaging a corresponding portion of a stationary contact of the circuit breaker.
As employed herein, the term “trip condition” refers to any abnormal electrical condition which could cause a circuit breaker or other electrical switching apparatus to trip expressly including, without limitation, an overcurrent condition, an overload condition, an undervoltage condition, or a relatively high level short circuit or fault condition.
As employed herein, the statement that two or more parts are “coupled” together shall mean that the parts are joined together either directly or joined through one or more intermediate parts.
As employed herein, the term “number” shall mean one or an integer greater than one (i.e., a plurality).
Continuing to refer to
As shown in
The interaction of the linking member 106 with the D-shaft 14 will now be described in greater detail. That is, the second end 110 of the linking member 106 includes a protrusion 118 having a first edge 120. The aforementioned shaft hub 112 includes a second edge 122 disposed at or about the recess 114 of the hub 112. It will, therefore, be appreciated that the linking member 106 is movable between a first position (
As best shown in
In the example shown and described herein, the circuit breaker housing 4 includes a side plate assembly 20, which in addition to the aforementioned first side plate 22, further includes a second side plate 24 extending outwardly from the housing 4 opposite and distal from the first side plate 22, and cam action pin 30. The cam action pin 30 extends laterally outwardly from the first side plate 22 toward the linking member 106 and, in particular, a cam surface 140 thereof. The cam action pin 30 cooperates with the cam surface 140 to move (e.g., without limitation, upward and downward from the perspective of
In the example shown and described herein, the operating mechanism 8 of the circuit breaker 2 further includes a poleshaft tripper pivot 150, which is movably disposed within an opening 160 of the linking member 106. The opening 150 is disposed between the first and second ends 108,110 of the linking member 106, as shown in
Accordingly, the disclosed secondary trip mechanism 100 provides a convenient and efficient mechanical link for interfacing with the circuit breaker poleshaft 10 to ensure sufficient additional tripping force is applied to effectuate tripping operation of the circuit breaker 2 in response to a trip condition.
While specific embodiments of the disclosed concept have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the disclosed concept which is to be given the full breadth of the claims appended and any and all equivalents thereof.