Thermal override for static trip circuit breakers
AssigneeGeneral Electric Company
InventorStephen F. Gillette
Life of this patent
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Abstract
A flux shifting type trip device, which is electrically activated under the control of a static trip unit to mechanically initiate tripping of a circuit breaker automatically in response to an abnormal current condition in a protected circuit, is equipped with a thermal responsive element operative to directly, mechanically activate the trip device and thereby initiate circuit breaker tripping automatically in response to an excessive ambient temperature condition within the circuit breaker enclosure.
Claims10
For incorporation in an electromechanical trip device including a permanent magnet for developing a holding flux to create a magnetic force on a plunger sufficient to hold the plunger in a retracted position against the bias of a spring and an electromagnet for selective electrical energization to develop flux in opposition to the holding flux, whereby the magnetic holding force on the plunger is diminished to the extent that the spring becomes overpowering, whereupon the plunger is propelled by the spring to an extended circuit breaker trip initiating position, a thermal trip override comprising a thermal-mechanical element acting to exert a force on the plunger aiding the spring force such as to overpower the magnetic holding force when the temperature becomes excessive whereupon the plunger is propelled to its extended, circuit breaker trip initiating position by the spring.
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 exert a force on said plunger aiding said spring whereby the magnetic force on said plunger is overpowered, enabling said spring to propel said plunger to its extended position.
Dependencies are inferred from the claim text.