Ambient temperature responsive trip device for static trip circuit breakers
AssigneeGeneral Electric Company
InventorEdward K. Howell
Life of this patent
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Abstract
A flux shifting circuit breaker trip device includes a permanent magnet for developing a holding flux to create a magnetic force on a plunger sufficient to hold it in its retracted position in opposition to a spring. An electromagnet energized under the control of a static trip unit develops flux in opposition to this holding flux, whereupon the spring becomes overpowering and propels the plunger to its extended position effecting a circuit protective trip function. Temperature responsive means are also included to increase the reluctance in a region of the holding flux path in response to an excessive ambient temperature condition within the breaker enclosure, whereupon the spring becomes empowered to motivate a thermal override trip function.
Claims13
In an electromagnetic trip device including a plunger reciprocally mounted for movement between a retracted position and an extended position, a spring biasing the plunger to its extended position, a permanent magnet developing a holding flux in a holding flux path including the plunger, the holding flux providing sufficient magnetic holding force on the plunger to hold the plunger in its retracted position against the bias of the spring, and an electromagnet selectively electrically energized to develop flux in the flux path opposing the holding flux whereby the magnetic holding force is diminished to the extent that the spring becomes overpowering and thus acts to propel the plunger to its extended position effective in initiating tripping of a circuit breaker, a thermal trip override comprising a temperature response element acting in response to an excessive ambient temperature condition within a circuit breaker enclosure to increase the magnetic reluctance of the holding flux path at a predetermined location therein, thereby to reduce the magnitude of the holding flux flowing in the plunger and thus reduce the magnetic holding force exerted thereon to the extent that the spring becomes overpowering and the plunger is propelled by the spring to its trip initiating, extended position.
A thermal trip override device operative to trip a circuit breaker in response to a high ambient temperature within the circuit breaker enclosure, said device comprising, in combination:
- A. a plunger of high magnetically permeable material mounted for movement between a retracted position and an extended position;
- B. a spring biasing said plunger to its extended position effective in initiating tripping of the circuit breaker;
- C. a permanent magnet for developing holding flux flowing in a magnetic circuit including said plunger, said holding flux developing sufficient magnetic force to hold said plunger in its retracted position against the bias of said spring;
- and
- D. temperature responsive means acting in response to a high ambient temperature condition within the breaker enclosure to insert a high magnetic reluctance in said magnetic circuit, whereby to reduce the holding flux flowing in said plunger to the extent that said spring becomes empowered to propel said plunger to its extended position.
Dependencies are inferred from the claim text.