Patent Application
20160141137
The subject matter disclosed herein relates to circuit breakers and, more particularly to a magnetic trip latch mechanism for circuit breakers for tripping the circuit breaker in the event of a short circuit condition.
Circuit breakers are used to protect equipment from overcurrent situations caused, for example, by short circuits or ground faults in or near such equipment. In the event an overcurrent condition occurs, electrical contacts within the circuit breaker will open, stopping the flow of electrical current through the circuit breaker to the equipment. Circuit breakers may be designed for high quiescent currents and high withstand currents. To maintain a high withstand current rating, the contacts must be clamped closed at the current withstand rating. On the other hand, at the short circuit current level, the contacts must be capable of opening quickly. The drawback of having the contacts clamped close is that the contacts may not be able to open quickly at the short circuit current level.
According to one aspect of the invention, a magnetic trip mechanism for a circuit breaker includes an electrically conductive strap having a first wall portion and a second wall portion that define an interior space there between. Also included is a flux block disposed at least partially within the interior space, and rotatable in response to a short circuit condition of the circuit breaker. Further included is a trip lever operatively coupled to the flux block. Yet further included is a trip latch moveable between a latched condition and an unlatched condition with a handle, wherein movement of the trip lever occurs in response to the short circuit condition and causes movement from the flux block to actuate the trip latch to the unlatched condition.
According to another aspect of the invention, a circuit breaker includes a rotatable contact arm having a moveable contact operatively coupled thereto. Also included is an electrically conductive strap and a fixed contact operatively coupled to the electrically conductive strap. Further included is a flux block at least partially surrounded by the electrically conductive strap, wherein rotation of the flux block is actuated during a short circuit condition of the circuit breaker. Yet further included is a trip lever operatively coupled to the flux block. Also included is a trip latch moveable between a latched condition and an unlatched condition with a handle, wherein movement of the trip lever occurs in response to the short circuit condition and causes movement from the flux block to actuate the trip latch to the unlatched condition.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
Referring to
The circuit breaker 10 includes a magnetic trip mechanism 20 configured for sensing a predetermined high withstand current in the circuit breaker 10 and maintaining contact between contact structures (not illustrated) during the predetermined high withstand current. The magnetic trip mechanism 20 is also configured for sensing a predetermined short circuit current and quickly tripping an operating mechanism that the handle 14 is configured to operate in order to separate the contact structures in response to the short circuit current. In particular, the handle 14 is configured to manipulate a rotatable contact arm 24 having a moveable contact operatively coupled to an end of the rotatable contact arm 24. The load strap 16 includes a fixed contact operatively coupled thereto. The fixed contact is configured to be in contact with the moveable contact of the rotatable contact arm 24 to allow electrical current to flow from the line strap to the load strap 16.
Referring now to
The flux block 26 is formed of a material (e.g., steel) that concentrates magnetic flux during a short circuit condition. The concentration of the magnetic flux imparts movement of the flux block 26 during a short circuit condition. In one embodiment, the interior space 38 of the load strap 16 is configured to allow rotation of the flux block 26 (
As the flux block 26 is moved, whether translationally, rotationally or both, the flux block 26 imparts movement of a trip lever 40 to which the flux block 26 is operatively coupled to. The operative coupling of the trip lever 40 and the flux block 26 may be a directly coupled arrangement or may include one or more intermediate coupling elements, such as the coupling element 42 illustrated in FIGS. 4-6. Although a single trip lever is described herein for purposes of simplicity, it is to be understood that an additional trip lever is operatively coupled to the flux block 26 at an opposite side of the flux block 26. The trip lever 40 extends from a first end 44 to a second end 46. The operative coupling of the trip lever 40 to the flux block 26 is made proximate the second end 46 in the illustrated embodiment, however, other locations are contemplated, such as closer to a midpoint of the trip lever 40.
As the trip lever 40 is rotated and/or translated, the first end 44 interacts with a trip latch 48 (
At this point, it should be appreciated that the magnetic trip of the circuit breaker 10 is solely facilitated by the magnetic trip mechanism 20. Advantageously, an instantaneous override is provided to achieve current limiting at lower fault levels. By clearing the fault quickly with simply magnetic flux-initiated movement, less damage to contacts is observed.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
