OPERATION CONTROL UNIT OF INDUCTION MOTOR

摘要

PROBLEM TO BE SOLVED: To provide an overvoltage protecting device of high reliability at a low cost, related to an overvoltage protecting device of a speed control unit connected with the secondary circuit of a wound rotor induction motor. SOLUTION: An overcurrent protecting fuse 3 is fused by a short-circuit current which flows, when a surge absorber 5 operates. A transient overvoltage is shared by a resistor 4 and the surge absorber 5. The speed control unit 6 is always protected by an operating voltage of the surge absorber.