Electricity: electrical systems and devices – Safety and protection of systems and devices – Motor protective condition responsive circuits
Patent
1978-10-02
1981-05-05
Salce, Patrick R.
Electricity: electrical systems and devices
Safety and protection of systems and devices
Motor protective condition responsive circuits
361106, H02H 708, H02H 504
Patent
active
042662575
ABSTRACT:
A motor overheating protection circuit includes an enabling circuit which responds to a trigger signal provided by a reset circuit upon application of power to the protection circuit to enable a motor drive circuit to effect energization of the motor. A temperature sensing circuit provides a control signal indicative of the temperature of the motor, and should the control signal exceed the set point of a threshold detecting circuit of the enabling circuit, indicative of overheating of the motor, the enabling circuit inhibits the motor drive circuit deenergizing the motor. Once the motor has been deenergized as the result of an overheating condition, the reset circuit maintains the enabling circuit locked out until the protection circuit is deactivated and then reactivated. If the sensor or its input leads are open, then the control signal provided by the temperature sensing circuit will exceed the detection threshold of the threshold detecting circuit and the enabling circuit will maintain the motor deenergized. If the sensor or its input leads are short circuited, then the control signal provided by the temperature sensing network will be less than the threshold level for a minimum voltage detector circuit of the enabling circuit and the enabling circuit will maintain the motor deenergized.
REFERENCES:
patent: 3457460 (1969-07-01), Buiting et al.
patent: 3794858 (1974-02-01), Squiers
patent: 3909675 (1975-09-01), Hirsbrunner et al.
patent: 4028593 (1977-06-01), Newell
patent: 4075674 (1978-02-01), Squiers et al.
"I.C. Timer Plus Thermister Can Control Temperature" by Donald Dekold Electronics, Jun. 21, 1973, pp. 128 and 129. _
Johnson Controls Inc.
Salce Patrick R.
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