Patent Application
20100155136
This invention is directed generally to a transformer for a circuit breaker, and, more particularly, to a current transformer housing for routing conductors in a controlled manner.
Electrical current transformers are generally an integral part of some circuit breakers. For example, one type of transformers is included in ground fault circuit breakers, which are commonly used to protect people from electrical shocks due to line-to-ground current flow through a person's body. Ground fault circuit breakers are required to detect current flow between line conductors and ground at current levels on the order of about 5 milliamperes. These low current levels are much below the overload current levels required to trip conventional circuit breakers. In response to detecting of a ground fault current, the circuit breaker is tripped to prevent further flow of current through the protected circuit. Specifically, a movable contact of the circuit breaker is separated from a fixed contact to prevent further current flow.
The primary windings for this type of transformer are the conductors of the distribution circuit being protected. Specifically, the conductors are encircled in a transformer housing core. For example, in a two-pole circuit breaker three conductors are routed through an opening in the transformer housing: two line conductors (i.e., line one and line two) and the neutral conductor. In a three-pole circuit breaker four conductors are routed through the opening: three line conductors and the neutral conductor.
During normal conditions, current flowing in one direction through a line conductor will return in the opposite direction through the neutral conductor. This produces a net current flow of zero through the transformer and, accordingly, a multi-turn winding provides no output. If, however, a fault is established between one of the line conductors and the ground, more current will flow in one direction through the transformer than in the other direction, producing a current imbalance. The current imbalance produces uncancelled flux in the transformer's core, resulting in an output in the multi-turn winding that trips the circuit breaker mechanism.
One problem associated with some transformers is that conductors and/or terminal assemblies cannot be properly routed through the transformer housing. For example, in some transformers the routing of a conductor may be possible only before any terminals or lugs are welded to the conductor. Such assembly restrictions result in difficult and rigid assembly methods, which are likely to increase manufacturing time and cost.
Another problem associated with some transformers, is that the physical position of the conductors and/or terminal assemblies cannot be accurately controlled within the space of the transformer through which they are being routed to achieve a required level of milliamperes sensing. Accordingly, the functionality and/or reliability of the transformer can be greatly reduced.
What is needed, therefore, is a transformer housing for a circuit breaker that addresses the above-stated and other problems.
In an implementation of the present invention, a circuit breaker includes a breaker housing, a transformer housing, and a plurality of conductor locators. The transformer housing is enclosed within the breaker housing and has an opening for receiving a plurality of conductors. The plurality of conductor locators is located adjacent to the transformer housing and is movable between an open position and a closed position. The plurality of conductors is generally centered in the opening of the transformer housing when the conductor locators are in the closed position.
In an alternative implementation of the present invention, a ground fault multi-pole circuit breaker assembly includes a circuit breaker housing for enclosing a multi-pole circuit breaker assembly, and a transformer housing mounted inside the circuit breaker housing. The transformer housing has an internal opening for receiving a plurality of conductors. Each of the conductors has an end fastening component, the end fastening component being attached to the respective one of the conductors prior to the respective one of the conductors being received within the internal opening. A pair of conductor locators is mounted to the transformer housing, each of the pair of conductor locators having a fixed end and movable end. The movable end of the conductors is movable between an open position and a closed position. The conductors are forced in close proximity to each other in a generally centered position of the internal opening when the pair of conductor locators are moved to the closed position, thus providing an improved sensing capability in the milliamp range.
Additional aspects of the invention will be apparent to those of ordinary skill in the art in view of the detailed description of various embodiments, which is made with reference to the drawings, a brief description of which is provided below.
The invention may best be understood by reference to the following description taken in conjunction with the accompanying drawings.
Although the invention will be described in connection with certain preferred embodiments, it will be understood that the invention is not limited to those particular embodiments. On the contrary, the invention is intended to include all alternatives, modifications and equivalent arrangements as may be included within the spirit and scope of the invention as defined by the appended claims.
Referring to
A test button 106 also protrudes through the circuit breaker housing 102. The test button 106 can be pressed to perform, for example, self-diagnostics tests related to a microprocessor of the circuit breaker 100.
The circuit breaker housing 102 can include several housing elements. For example, the circuit breaker housing 102 can include a housing base 108a, a housing enclosure 108b-108d for each of the three poles of the circuit breaker 100, and a housing cover 108e. In alternative embodiments, any number of housing elements can be used to form the circuit breaker housing 102.
Referring to
The conductor locators 114a, 114b are pivotable between an open position (as illustrated in
The conductor wires 112a-112c include respective power terminals 122a-122c, which are welded on one end of the conductor wires 112a-112c prior to insertion of the conductor wires 112a-112c through the opening 116. The conductor wires 112a-112c further include respective power contacts 124a-124c, which are welded on another end of the conductor wires 112a-112c prior to insertion of the conductor wires 112a-112c through the opening 116.
Referring to
In the open position, the conductor locators 114a, 114b are positioned outwards, away from the opening 116, such that they do not obstruct the opening 116. The conductor wires 112a-112c are easily inserted through the opening 116 when the conductor locators 114a, 114b are in the open position. The illustrated opening 116 is large enough to permit insertion of the conductor wires 112a-112c and the power terminals 122a-122c or the power contacts 124a-124c. In other words, the opening 116 can be referred to as an “oversized” opening that is dimensioned such that a gap can be present between the conductor wires 112a-112c and the diameter of the opening 116 after the conductor wires 112a-112c have been inserted through the opening 116.
Referring to
The right conductor locator 114b has been pivoted in a counter-clockwise direction to place it in the closed position. Similar to the left conductor locator 114a, the right conductor locator 114b is also secured in the closed position via the locking element 120.
In the closed position, the conductor wires 112a-112c have been moved in close proximity to one another. In fact, the conductor wires 112a-112c are now in contact with each other and are centrally positioned in the opening 116.
The centering mechanism of the conductor locators 114a, 114b provides increased flexibility during manufacturing and assembly of the circuit breaker 100. The opening 116 is large enough to permit the insertion of the conductor wires 112a-112c together with the power terminals 122a-122c or the power contacts 124a-124c. However, because of the relatively large size of the opening 116, the conductor wires 112a-112c are now most likely to remain in positions too far away from each other to properly sense changes in current, e.g., a five milliamp change in current between a power conductor and a neutral conductor. The centering mechanism of the conductor locators 114a, 114b provides a solution to the positioning problem. After insertion of the conductor wires 112a-112c, the conductor locators 114a, 114b are instrumental in positioning the conductor wires 112a-112c close enough to each other such that the required current change can be adequately sensed.
Referring to
Providing two pairs of conductor locators, instead of a single pair, is likely to increase the distance over which conductor wires 212a-212c are in close proximity with each other and centered in the transformer housing 210. For example, if a single pair of conductor locators is used, the conductor wires 212a-212c may likely only be in close proximity with each other near the single pair of conductor locators. Having two pairs of conductor locators increases the likelihood that the conductor wires 212a-212c are in close proximity with each other for at least the entire distance separating the two pairs of conductor locators 214a, 214b and 215a, 215b. Thus, based on the increased distance over which the conductor wires 212a-212c are properly positioned, the sensing performance of the transformer is likely to increase.
Referring to
The conductor locators 314a, 314b include, respectively, a locator tab 317a, 317b. The locator tabs 317a, 317b can be grasped by an operator to pivot the conductor locators 314a, 314b between the open and closed positions.
According to other alternative embodiments, the conductor locators can move in any manner between the open position and the closed position. For example, the conductor locators can slide (instead of pivoting) between the open position and the closed position.
While particular embodiments, aspects, and applications of the present invention have been illustrated and described, it is to be understood that the invention is not limited to the precise construction and compositions disclosed herein and that various modifications, changes, and variations may be apparent from the foregoing descriptions without departing from the spirit and scope of the invention as defined in the appended claims.
