Induction motor with two independent stator windings - has windings supplied from fixed and variable frequency sources for speed control

摘要

The cage type induction motor is built with two independent three phase stator windings (9,10). One winding is supplied at mains frequency, the other is connected to a variable frequency supply. By constructing the machine in this manner, the power output of the necessary frequency converter can be reduced and consequently the overall efficiency increased. The motor speed is determined by the sum of the frequencies, and the number of poles. The stator windings may be in adjacent cores or be made with one winding over the other. If the variable frequency winding is connected for the opposite rotation to that of the fixed frequency one speed control down to standstill can be achieved. Start up is normally on fixed frequency.