Impacts of Number of Poles and Slots on Armature Reaction and Performance of Ironless Permanent Magnet Motors

Abstract

Armature reaction is considered as one of the challenging problems in on-load permanent magnet (PM) motors. Reducing the undesirable impacts of the armature reaction is necessary to improve the PM motors performance. The ironless stator PM motor is known as an appropriate choice for low armature reaction. Although in these motors, disturbing high-order harmonics of armature reaction are removed, improper winding distribution still causes asynchronous field harmonics. Choosing the number of poles and slots leads to various structures with different armature windings for ironless stator PM motors. Impacts of armature reaction upon the performance of the motors with different structures are addressed in this article. This is done using precisely and quickly by a combined analytical model. This model can model the PMs magnetic fields, the air gap magnets field, and the armature reaction field. The finite element modeling (FEM) results confirm the accuracy of the proposed analytical model. Then, the analytical method and FEM are used to predict the performance of the ironless stator PM motors with the different numbers of poles and slots. This makes it possible to suggest an appropriate number of poles and slots for lower armature reaction, lower disturbed voltage harmonics, lower torque ripple, higher output power, and higher winding distribution factor.

Keywords:

• analytical method
• armature reaction
• finite element method
• ironless permanent magnet motor
• magnetic field

Additional information

Notes on contributors

Morteza Mikhak-Beyranvand

Morteza Mikhak-Beyranvand received the B.Sc. degree from Hadaf University, in 2010, the M.Sc. degrees from Malek-Ashtar University of Technology, in 2013, and Ph.D. degrees from Lorestan University, in 2019, all in electrical engineering (in Iran). He is currently an assistant professor in the department of electrical engineering, Technical and Vocational University (TVU), Iran. His research interests include design and analysis of electrical machines and electromagnetic-thermal modeling of power transformers.

Jawad Faiz

Jawad Faiz received the Ph.D. degree from the University of Newcastle upon Tyne, UK, in 1988 in electrical engineering and at the same year he joined University of Tabriz as faculty member. Since February 1999, he has been a Professor with the School of Electrical and Computer Engineering, College of Engineering, the University of Tehran, Tehran, Iran, where he is currently the Director of the Center of Excellence on Applied Electromagnetic Systems. He is the author of 280 papers in international journals and 290 papers in international conference proceedings. His teaching and research interests include switched reluctance and variable reluctance motor design, design and modeling of electrical machines and drives, transformer modeling and design, and fault diagnosis in electrical machines and electromagnetic-thermal modeling of power transformers.

Javad Khoshtarash

Javad Khoshtarash received the B.Sc. degree from University of Tabriz, Iran, in 2009, and the M.Sc. degrees from Malek-Ashtar University of Technology, Iran, in 2012. His research interests include design and analysis of electrical machines and finite-element modeling.