Variable frequency drives with two-speed asynchronous electric motors

The paper considers the issues of enhancing immunity of the variable frequency electric drives (VFDs) c to short-term power supply interruptions. It proposes the concept of electric drives of the frequency converter-two-speed asynchronous motor system with switching structures. It is proved that development of VFDs with supply from two inputs is reasonable as they almost exclude simultaneous failures of power supply. Electric drive with two frequency converters, high and low speed windings supplied from independent inputs and electric drive with the frequency converter featuring two DC links are considered. The paper provides the VFD distinctive feature of which is switching the frequency converter from the high speed winding to the lowspeed one (and vice versa) dependent on the unit performance. It represents results of experimental research of the developed VFDs.