Cogging torque in SPM machine with segmented stator

• Published in: Compel Vol. 35; no. 2; pp. 641 - 654
• Main Authors: Shen, Jian-Xin, Cai, Shun, Yuan, Jian, Cao, Shuai, Shi, Cen-Wei
• Format: Journal Article
• Language: English
• Published: Bradford Emerald Group Publishing Limited 07-03-2016
• Subjects: Air gaps; Cogging; Design engineering; Electrical & electronic engineering; Electrical engineering; Electromagnetic fields; Engineering; Finite element analysis; Finite element method; Flux density; Infrared radiation; Joining; Magnetism; Manufacturing; Mathematical analysis; Mathematical models; Motors; Permanent magnets; Segmentation; Segments; Stators; Studies; Torque; Cogging torque; Analytical model; Finite element method (FEM); Surface-mounted permanent magnet (SPM); Segmented stator core
• ISSN: 0332-1649; 2054-5606
• DOI: 10.1108/COMPEL-02-2015-0101

Purpose
– The purpose of this paper is to evaluate the cogging torque in a surface-mounted permanent magnet (SPM) machine with both uniformly and non-uniformly segmented stator cores and to find out the optimal solution of stator core segmenting.
Design/methodology/approach
– The cogging torque with segmented stators is synthesized from a single slot model, and analytical prediction is given to analyze the cogging torque with both uniformly and non-uniformly segmented stators. Finite element method (FEM) is used to figure out the electromagnetic field and validate the analytical prediction. Moreover, models with various shapes and positions of connecting tongues between the stator core segments are explored to achieve the optimal design.
Findings
– The cogging torque is found to be greatly related to the number of segments and the electrical angle between adjacent additional air gaps caused by the tolerance of stator segments. Different shapes of the connecting tongues are tested and proved to be of great importance to the flux density, both radial and tangential, and therefore affect the cogging torque. Finally, position of the connecting tongues is perceived to have little influence on the performance of machine.
Practical/implications
– By utilizing analytical prediction and FEM calculation, the optimal solution is discussed to minimize the cogging torque in the SPM machine from the perspective of the stator core segmentation.
Originality/value
– This paper establishes formula of cogging torque with segmented stators and predicts the variation of cogging torque with analytical method. Besides, different combinations of segments are compared and measures to reduce the cogging torque produced by the segmentation are proposed.