Static frequency converter for three=phase async. machine - has input rectifier and two parallel output static inverters only one of which operates for low output currents

摘要

The static frequency converter, for supplying an asynchronous 3-phase machine, has a maions commutated rectifier, a d.c. coupling circuit and a self-commutating static inverter with capacitor/diode commutation. The static inverter (3) consists of 2 or more parallel sub-inverters (4, 5) connected together on the d.c. side and the a.c. side. At small output currents only one of the parallel sub-inverters is operated. The advantage lies in avoiding damaging voltage spikes at the thyristors and in reducing the max. operating frequency.