Current measuring system for use in voltage source inverter for measuring current of induction motor, has resistor for determining inverter module output current from determined alternating current portion and intermediate circuit current

摘要

The system has a load sided alternating current motor (2) with a resistor (7) for determining direct voltage intermediate circuit current (Idc) and phase current (Ie) of a bridge section of an inverter module (1). Another resistor (8) determines alternating current portion of determined emitter current and determines output current of the inverter module from the determined alternating current portion and the determined circuit current. A sigma delta converter (10) is connected to an integrator electrically parallel to a negative bus bar (5).