with three or more levels of voltage

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 DC to AC converters or inverters (H02P27/05 takes precedence) > with pulse width modulation > with three or more levels of voltage