New Optimized Fractional Slot Concentrated Winding Design for Torque Ripple Minimization in Permanent Magnet Machine

Abstract

This paper presents a new optimized fractional slot concentrated winding (FSCW) design for torque ripple minimization in permanent magnet motors through space harmonic reduction. The proposed design offers the minimum total harmonics distortion in the magnetomotive force (MMF) produced by the winding whereas winding factor of the working harmonic component is set to the maximum value. A detailed mathematical derivation of the winding function is presented for general symmetrical FSCW using Fourier series expansion. The optimization methodology presented for the new optimized FSCW design results in optimal number of conductors at optimal slot positions while keeping slot pitch equal in the core design. The harmonic analysis of various examples of FSCW is presented which shows a significant reduction in the non-working harmonics in the proposed optimized design. A 24-slot 22-pole permanent magnet synchronous motor is designed and analyzed using the two-dimensional finite element method. The magnetic analysis of motors shows that the non-working harmonics in the air-gap flux distribution are minimized in the case of proposed design as obtained from the analysis of winding functions. The dynamic analysis shows a substantial improvement in the performance of proposed FSCW machine over the conventional machine.

Keywords

• finite element analysis
• harmonic analysis
• optimization
• permanent magnet motors
• torque