Current sensing protector system for A. C. motors

Details Current sensing protector system for A. C. motors Current sensing protector system for A. C. motors

1974-04-25

1976-01-13

Trammell, James D.

317 33SC, 317 46, H02H 7085

Patent

active

039327892

ABSTRACT:
The specification discloses a system for preventing current overload in a three phase dual speed A. C. motor in both high and low speed modes. The system includes current transformers for sensing the current level in each of the three phases applied to the motor. Circuitry is provided to detect the occurrence of a current level above each of a plurality of levels depending upon the speed of the motor. Circuitry is responsive to the detection of an overload current level in order to operate a switching transistor to terminate conduction of a triac in order to terminate the current flow through the phases. A light emitting device is connected to the switching transistor to emit light upon the occurrence of the overload condition. A light sensor senses operation of the light emitting device and initiates a timing cycle by a timing circuit during which the triac may not be rendered conductive.

REFERENCES:
patent: 3368129 (1968-02-01), Chausse et al.
patent: 3379939 (1968-04-01), Obenhaus
patent: 3696288 (1972-10-01), Carman
patent: 3742302 (1973-06-01), Neill
patent: 3742303 (1973-06-01), Dageford

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