using AC supply for both the rotor and the stator circuits, the frequency of supply to at least one circuit being variable

Full Title

Arrangements or methods for the control of AC motors characterised by the kind of supply voltage (of two or more motors H02P5/00; of synchronous motors with electronic commutators H02P6/00; of DC motors H02P7/00; of stepping motors H02P8/00) > using variable-frequency supply voltage, e.g. inverter or converter supply voltage > using AC supply for both the rotor and the stator circuits, the frequency of supply to at least one circuit being variable