Patent ID: 6927549

Claim:
An electric motor control unit mounted in an automotive vehicle comprising: a motor used for driving a cooling fan of a radiator, the motor being supplied with electrical power from a battery, the motor having a variable rotational speed; a temperature sensing element disposed at a position of the motor control unit where abnormal heat is generated as a result of overcurrent supplied to the motor; and a rotational speed control means for reducing the rotational speed of the motor without stopping the motor based on detection of abnormal heat generation by the temperature sensing element, wherein the rotational speed control means has a plurality of relays arranged between the battery and the motor, and at least one of the relays permits a switching operation based on detection of abnormal heat generation to control electrical power supplied to the motor so as to reduce the rotational speed of the motor, and wherein the temperature sensing element is a thermistor, one end of which is grounded and the other end of which is connected to the one of relays, the thermistor having a resistance which varies with its temperature, and the one of the relays performs switching operation in response to the thermistor resistance varied with abnormal heat generation of the motor.