Temperature protective circuit for protecting electric motor from overheating

摘要

The circuit includes a series circuit of PTC thermistors with stepped rated temperatures. The thermistor(s) having low rated temperature is bridged by electrical components to maintain the total resistance of the circuit constant, up to the rated temperature of the thermistor with the next highest temperature rating. The thermistor (2) with low rated temperature is bridged by a resistor (R1) so that switch-off is not triggered until the rated temperature of the thermistors (1,1',1'') with the highest rated temperature is reached.