A Control Method of an Inverter- Fed Six- Phase Pole Change Induction Motor for Electric Vehicles

Abstract

In attempt to improve the constant power operation properties of the induction motor (hereafter, IM) for electric vehicles, we have developed a six- phase pole change IM (hereafter, six-phase PCIM). The six- phase PCIM can expand the constant power operation range without increasing the volume and current of IM. This advantage is realized by making use of the difference of the IM's maximum torque in the dissimilarity in the number of poles.
This paper can be summarized as follows:
A six- phase PCIM which can be operated as 4-pole and 8-pole is smaller than a 4-pole IM with the same rating.
The method of vector control based on the six- phase to two pairs of rotational d- q axis transformation is established.
When a six-phase PCIM is operated with a six-phase inverter, a mechanical contactor to change the number of poles is not necessary and the pole change is carried out automatically at the proper speed.
The pole change can be done smoothly without the large torque variation by the technique of controlling the flux levels of both modes independently.
The characteristics of the proposed control method are shown through the simulations and experimental results, and the usefulness of this control method for the electric vehicle drive system is made clear.