RETARDER

PURPOSE: To set the actual temperature of a rotor accurately by correcting the output from a temperature sensor depending on the r.p.m. of the rotor. CONSTITUTION: In a control section 7, a correction magnification value table is provided for a correction means 10 and a temperature detected through a temperature sensor 2 is multiplied by a correction magnification value depending on the r.p.m. of the rotor detected through a rotation detecting means 9 thus detecting an actual temperature of a rotor. An AC voltage generated from an exciter 5 is rectified through a rectifier circuit 6 and applied to a switching element 8. Based on an actual temperature of rotor obtained by correcting a temperature detected through the temperature and information from a current sensor 3, the switching element 8 is subjected to PWM control at the control section 7 and a constant current is fed to a main winding 4. When the actual temperature of rotor exceeds a predetermined level and when a current higher than a predetermined level is detected through the current sensor 3, the control section 7 delivers a signal for turning the switching element 8 OFF to interrupt current supply to the main winding 4 thus preventing temperature rise of the rotor.