Design Considerations for an Active–Reactive Induction Motor for Medium-Voltage Applications

The active-reactive induction motor (ARIM) has been introduced in the literature as a low-cost and high-efficiency alternative to the synchronous motor in load commutated inverter (LCI) fed drives. ARIM is a squirrel cage machine with two sets of dissimilar three-phase stator windings. While one winding is rated for high voltage and power, the other winding is rated for a lower voltage and power. The low-voltage winding fed from a voltage source inverter (VSI) supplies only reactive power to the machine such that a leading power factor appears at the high-voltage terminals, enabling LCI-fed operation at this winding. Since the ARIM is fundamentally an induction motor, the conventional induction machine design process is applicable. However, due to the nonconventional arrangement of stator windings and being intended specifically for an LCI-fed topology, this new class of induction machines requires some critical design considerations. It is shown in this article that the leakage inductances play a pivotal role in determining the ratings of the low-voltage windings and the VSI. Therefore, an iterative design procedure to obtain the correct ratings for the flux winding and the low-voltage components is proposed. It is also required to know the correct value of the leakage inductance in order to design the control loops for reliable operation. This article proposes experimental methods to determine these leakage inductances. The proposed methods are validated by designing a 3.3-kV, 75-kW prototype and experimental results are presented.