JPS5783190A - Operation system of induction motor - Google Patents

Abstract

PURPOSE:To compensate faults in each system by combining two systems of a power converter relying on power source commutation to pursue alternating operation. CONSTITUTION:In the low speed region where a signal level of a speed setting device 12 is lower than a reference value of any of changeover level setting units 14 and 14', both comparators 15 and 15' do not output any signal whereas a signal PL is generated from a switching signal generator 16. With this constitutes connection of a major part main circuit constitutes a single-phase half- wave type cyclo converter. Next, when a motor speed reaches about one third of the mains frequency corresponding to the upper limit of the cyclo converter, the output of the speed setting device 12 becomes larger than the output of the switching level setting unit 14, the comparator 15 operates, and the switching signal generator 16 generates a signal PM. As a result, the connection of a major part main circuit constitutes a star connection triac type primary voltage control circuit mode. Moreover, when it has reached a fixed speed around the upper limit, a switching signal generator 16' generates a signal PH, and the connection of the major part main circuir constitutes a delta connection triac type primary voltage control circuit mode.