Adagrad Algorithm based Optimal Slot-pole Selection for Reduced Inductance Harmonics in Concentrated Wound Multiphase PMSM.

Abstract

Fractional slot concentrated windings (FSCW) permanent magnet synchronous machines (PMSM) have high content of space harmonics in the magnetomotive force (MMF) due to which the harmonic inductance is much larger than the magnetizing inductance [1]. These inductance harmonics lead to high torque ripple and low power factor. In case of FSCW, the coils are full pitched and cannot be chorded like in distributed windings to reduce inductance harmonics and also a suitable rotor structure have small impact on reduction of these harmonics. However, the space harmonic content in the FSCW PMSM vary significantly with the choice of slot-pole combination. Thus, the inductance harmonics can be modeled and minimized using an optimal choice of machine phases (m), stator slot numbers (S) and rotor poles (P). State of the art: [2] has presented the selection of slot, pole and phase numbers for reducing harmonic leakage inductance specifically for single layer CW PMSM. In [3], a detailed procedure for slot-pole selection based on inductances for single and double layer windings are provided. However, these are restricted for odd phase numbers and the selection process is time consuming. In this paper, the impact of winding layers, phase belt, slots, poles, and phase numbers on inductance harmonics has been studied. Further, an Adapative gradient (Adagrad) algorithm based approach is implemented to optimally select these parameters with little prior knowledge about the structural data.