Method for reducing switching losses in current-injecting frequency converters

摘要

The current injection of the present pulse converter having a voltage intermediate circuit is implemented by measuring and regulating each individual phase current via 3-point regulators which have hysteresis. Since the switching losses which occur in the power switches (power circuit breakers) during pulsed operation are proportional to the switching frequency, the invention is therefore based on the object of minimising the switching frequency relating to the driving of the power switches, while maintaining the quality of the phase currents governed by the hysteresis band. In particular, the alternating switching which additionally loads the power semiconductors as a result of ringing currents is to be avoided as far as possible. According to the invention, this is achieved by means of range splitting (BAS) and range gating (masking, blanking) (BAT), according to which alternating switching operation is permitted between in each case one upper and one lower switch for only very small currents and, in addition, as a function of the rotation direction, only until the zero crossing of the nominal value. IMAGE