Electricity: magnetically operated switches – magnets – and electr – Electromagnetically actuated switches – Automatic circuit-interrupting devices
Patent
1974-04-29
1976-03-16
Broome, Harold
Electricity: magnetically operated switches, magnets, and electr
Electromagnetically actuated switches
Automatic circuit-interrupting devices
335174, H01H 7348
Patent
active
039449530
ABSTRACT:
A current limiting circuit breaker having for each pole, a pair of main contacts separable upon operation of a thermally and electromagnetically operable tripping device and a pair of auxiliary contacts for current limiting in series with the main contacts and in parallel with a transformable resistor having a positive temperature coefficient of resistance. The auxiliary contacts are separable when an electromagnet is energized by a fault current which simultaneously energizes a field magnet to produce a transverse magnetic field across the auxiliary contacts and the arc formed between them when separating. This simultaneous action of electromagnet and field magnet coacting for rapid contact separation and lengthening of the arc upon flow of a fault current serves to increase arc voltage almost instantaneously to that of the source, about which time the fault current is totally shunted into the resistor. The tripping device for the main contacts includes a main trip lever for latching engagement with an armature, releasable upon energization of a magnetic core due to a fault current. It also includes a second trip lever normally latched by a rotatable trip bar, which is rotated to unlatching position by a bimetal when deflected due to prolonged overload conditions. When the second trip lever is unlatched, it strikes the armature thereby releasing it from latching engagement with the main trip lever allowing the tripping device to open the main contacts.
REFERENCES:
patent: 3032629 (1962-05-01), Uecker
patent: 3068379 (1962-11-01), Cole
patent: 3136921 (1964-06-01), Dorfman et al.
Broome Harold
Kettelson Ernest S.
Rathbun Harold J.
Square D Company
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