| Abstract |
The paper deals with a new circuit for induction motor speed control which has an invertor capable to produce reactive
power. The circuit comprises of a 3-phase thyristor bridge and a chopper in the dc circuit. Forced commutation is performed by means of one capacitor and six auxiliary thyristors. The firing pulses are synchronized with the supply voltage. Only one synchronizing transformer is used. The capacitor voltage is monitored and used for switching on thyristors. The system is controled by two parameters, phase shift and chopper conducting angle. Consequently several modes of operation and designing philosophies are possible. The most significant features of the new system are: full range of regulation and direct starting with minimal size of the transformer, improved power factor, and generation reactive power which can be regulated independently of speed-control in some range of regulation. The latter feature justifies to consider the invertor as a two-function convertor. Some of the operating strategies have been discussed. |
