Electricity: electrical systems and devices – Safety and protection of systems and devices – Circuit interruption by thermal sensing
Patent
1985-11-20
1987-07-28
Pellinen, A. D.
Electricity: electrical systems and devices
Safety and protection of systems and devices
Circuit interruption by thermal sensing
361 24, 361 31, H02H 708
Patent
active
046835156
ABSTRACT:
A motor overload protection system (OL) that has a speed of operation fast enough so that it will always trip before the power switch (MC) has had time to operate if the turn-on control means (ON) is operated under overload conditions. In one version, modules (OL1,OL2) are provided having PTC thermistor sensors (PTC1,PTC2) bonded to resistance heaters (H1,H2) connected in the motor power circuit (L1,L2,L3), these sensors being supplied from a current source (CT) and being effective to shunt current to a protective trip device (TR) upon occurrence of an overload condition, there being an ambient temperature compensating PTC themistor (PTC3) in series in the sensor circuit (OLC). In another version, a thermal mass (TM) is preheated above ambient temperature by an ambient temperature compensating PTC thermistor (ATC) operated above its switching temperature level and a sensor PTC thermistor (ST) and a heater (HT) are also thermally coupled to the thermal mass (TM) with a bias resistor (R1) connected to the sensor thermistor (ST) to provide a step voltage output (OUT) on overload. The heater may be a PTC thermistor (HT) having a higher switching temperature for self-shutoff on higher than usual overload or may be a resistance heater (H3) with a PTC thermistor (TP) in series therewith for self-shutoff.
REFERENCES:
patent: 2438495 (1948-03-01), Chatterjea
patent: 2896127 (1959-07-01), Seeley
patent: 3032690 (1962-05-01), Elliot
patent: 3526809 (1970-09-01), Obenhaus
patent: 3697863 (1972-10-01), Kilner
patent: 3794950 (1974-02-01), Kilner
patent: 3909675 (1975-09-01), Hirsbrunner et al.
Baran Michael S.
Beihoff Bruce C.
Judes Avie
Eaton Corporation
Pellinen A. D.
Rowe D. A.
Vande Zande L. G.
Williams Howard L.
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