Polyphase converter for induction motor control using the stator core saturation

This paper presents a new polyphase converter using saturation of the stator core of the induction motor. In this case, the commutation is performed by the saturation of the stator core even if the magnetic characteristic of the stator core is not of a sharp saturation. In order to compensate the effect of the slow saturation of the stator core, the base currents of the main transistors are supplied by independent dc sources. By changing the voltage of the dc sources, the ratio of the output voltage to the oscillation frequency can be arbitrarily controlled. The oscillation frequency is derived theoretically by idealizing each element of the converter. The phase rotation of the output voltages is determined by a simple R-C network with an auxiliary transistor.