Gradual Electronic Pole Changing Technique to Minimize the Circulating Currents During Pole/Mode Transition in Induction Motor Drive

This paper proposes a control strategy for the electronic pole changing (EPC) induction motor drive (IMD) for the transition between 3-ϕ,12-pole mode to 9-ϕ,4-pole mode. The proposed control strategy employs a gradual electronic pole changing (GEPC) technique which linearly demagnetizes the IMD winding from 3-ϕ,12-pole and magnetizes progressively to 9-ϕ,4-pole mode. The proposed GEPC technique is also compared with the instantaneous EPC technique for its performance. The proposed GEPC solution eliminates the issue of the circulating current, which exists in the instantaneous EPC technique and is responsible for negative torque generation during pole transition from 3-ϕ mode to 9-ϕ mode. Apart from eliminating the circulating current, the proposed GEPC strategy also sorts out various typical issues which exist in instantaneous EPC technique during pole/mode transition. The various issues in the instantaneous mode transition are (i) absence of interlocking between stator and rotor fields, (ii) oscillations in the flux between the 12-pole (3-ϕ) and 4-pole (9-ϕ), (iii) strengthening and weakening 4-pole formations in stator and rotor, (iv) distorted flux and pole formations, (v) dip in speed, and (vi) high oscillations/ripple content in torque and speed. Ansys simulation is done using Maxwell 2-D integrated with Twin-builder for EPC IMD for instantaneous and proposed GEPC techniques. Further, the paper presents the experimental results to validate the simulation studies.