JPS6426369A - Abnormality detecting device for inverter circuit - Google Patents

Abstract

PURPOSE:To form a device in small size and light weight by constituting a commutation detecting circuit of a differentiating circuit and a current detecting circuit and providing a commutation abnormality decision logical circuit which logically calculates an output of this detecting circuit in accordance with an operating condition of an inverter. CONSTITUTION:An inverter circuit is constituted of a three-phase transistor inverter circuit 20 and a capacitor 21 or the like. An abnormality detecting circuit of the inverter circuit is provided with a main circuit commutation detecting circuit 25 and a commutation abnormality decision logical circuit 31, constituting said detecting circuit 25 of a differentiating circuit 26 and a current detecting circuit 27 and said logical circuit 31 of a NOR circuit 32, NOT circuit 33, D type flip flops 34-35, AND circuit 36, OR circuit 37 and an edge detecting pulse generator circuit 38. Thus a potential change in an AC terminal, generated in the time of commutation and arc-through abnormality, is detected as a differential signal to be compared with a commutation instruction signal ; it is detected whether or not both the signals are inconsistent within a fixed time limit. As the result, the abnormality of commutation can be detected in good reliability.