FAULT DETECTOR FOR SECONDARY CIRCUIT IN WOUND-ROTOR TYPE INDUCTION MOTOR

摘要

PURPOSE:To reduce the cost of a wound-rotor type induction motor and to simplify the insulator between a secondary circuit and a secondary circuit fault detector by employing a current transformer for detecting the secondary current of the motor. CONSTITUTION:A signal proportional to the secondary current of a wound- rotor type induction motor 1 in each phase is produced by a current transformer 10, and the signal is rectified and smoothed via a peak value detection type rectifying and smoothing circuit 11. Since the production of the secondary current with the transformer 10 is not performed by a conductor connection such as a shunt, but is performed by the connection of the terminal to the terminal, the insulator between the terminals can be simply formed. The output of the circuit 11 is compared by a comparator 6, and when either one of the outputs of the comparator 6 becomes at least higher than the prescribed value, a relay 8 is operated.