FAIL-SAFE CIRCUIT FOR MULTI-ROTOR MOTOR SYSTEM

PURPOSE:To employ a simple single stage fail-safe circuit for the control of a plurality of motors. CONSTITUTION:Target values of torque TA*, PB* to be born are determined at the operating stages of induction motors 23A, 23B for a torque input command T* and then flux current commands ithetaAD, ithetaBD and torque current commands ideltaAD, ideltaBD are operated based on the TA*, TB*. These commands are subjected to D/A conversion at a two-phase/three-phase converting section 33 and then converted through a coordinate converter 38 into a three-phase AC signal for driving each motor through an inverter 22. An adder 14 adds the torque currents ideltaA, ideltaB for each motor. When the difference between the sum and the torque input command T* is larger than a decision criterion, a fail-safe signal is delivered to shut down the contactor 24 for each inverter 22. This circuit can detect a case where a value difference from a torque input command is operated due to the abnormality of a microcomputer constituting an operating stage positively while simplifying the circuitry.