TEMPERATURE PROTECTION CONTROL METHOD AND DEVICE THEREON FOR MOTOR STARTER

PROBLEM TO BE SOLVED: To make the fan of the overheat protection control device of a motor starter operate only when it is necessary and protect the whole equipment effectively and securely. SOLUTION: An ambient temperature sensor 36 supplies an ambient temperature signal in a motor starter 12. Pole temperature sensors 30, 32 and 34 generate temperature signals of respective output poles 22, 24 and 26. A microprocessor 28 is connected to the temperature sensors 30, 32, 34 and 36 and controls the motor starter 12 in accordance with the inputted temperature. Temperature signals are monitored periodically and compared with a fan-on reference value. When the temperature signal exceeds the reference value, a fan is turned on. The ambient temperature and pole temperatures are monitored and, if one of them exceeds a maximum temperature reference value, the motor starter is shut down unless override is set. If the motor starter is shut down, a time necessary for cooling down the motor starter is pursued and, if the time is too long, a maintenance flag is set to indicate the necessity of maintenance.