Multilayer Fractional Slot Pole-Phase Modulated Induction Motor Drives for Traction Applications

Abstract

With the advantage of pole-phase modulation (PPM), the multiphase induction motor drives facilitate the enriched range of speed-torque characteristics with a higher number of pole-phase combinations. In order to achieve this, a higher number of stator slots are required. For a wide range of medium and low power applications, having high number slots may not be possible because the number of slots decides the volume and weight of the drive. For addressing this slot dependency on the number of pole-phase combinations in PPM, a fractional-slot multilayer winding (FSMLW) is proposed in this article. For designing FSMLW, the number of layers per slot is a vital constraint and thus, in this article, the generalization of PPM is revised. For validating the proposed FSMLW concept in this article, a 15-Φ winding is designed with 36 slots, which is capable to run at three different pole-phase combinations, i.e., 1:3:5 speed ratios that make it suitable for electric vehicles and locomotive applications. In high pole mode, because of the less phase order, the magnitude of space harmonics will increase which results in high torque ripples. A carrier phase shifted sinusoidal pulsewidth modulation is used along with phase grouping concept for improving the harmonic profile of the air gap magneto motive force (MMF) as well as torque profile. The proposed FSMLW concept has been validated by using Ansys 2-D finite-element method or finite-element method (FEM) analysis as well as by performing the experiment on a laboratory prototype of 36 slot, 5hp 15-Φ multiphase induction motors drive.