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In recent years, with developing technology in the field of electrical machines, more efficient and high power density electric motors have been produced. The use of high energy efficiency motors gains importance due to the increase in global energy demand. The main purpose of this study was to design an Axial Flux Induction Motor (AFIM) with the same efficiency class as the Radial Flux Induction Motor (RFIM) in premium efficiency (IE3) class which is used commonly in industrial applications. Various AFIMs are designed with different rotor slot numbers and performance analyses as efficiency and torque ripple changes are investigated. It is known that torque ripple is one of the key parameters in electrical machine design which should be kept as low as possible without decreasing efficiency and torque. Accordingly, AFIMs’ rotor slots are skewed considering the stator and rotor slot numbers. The use of a Soft Magnetic Composites (SMC) material in design is also investigated. As a result of the analyses, many premium efficiency classes for AFIMs are obtained. In addition, using SMC material and skewing the rotor slots provides that torque ripples be reduced.

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Purpose – Due to high electromagnetic torque at low speed, vernier machines are suitable for direct-drive applications such as electric vehicles and wind power generators. The purpose of this paper is to present an exact sub-domain model for analytically predicting the open-circuit magnetic field of permanent magnet vernier machine (PMVM) including tooth tips. The entire field domain is divided into five regions, viz. magnets, air gap, slot openings, slots, and flux-modulation pole slots (FMPs). The model accounts for the influence of interaction between PMs, FMPs and slots, and radial/parallel magnetization. Design/methodology/approach – Magnetic field distributions for slot and air-gap, flux linkage, back-EMF and cogging torque waveforms are obtained from the analytical method and validated by finite element analysis (FEA). Findings – It is found that the developed sub-domain model including tooth tips is very accurate and is applicable to PMVM having any combination of slots/FMPs/PMs. Originality/value – The main contributions include: accurate sub-domain model for PMVM is proposed for open-circuit including tooth-tip which cannot be accounted for in literature; the model accounts the interaction between flux modulation pole (FMP) and slot; developed sub-domain model is accurate and applicable to any slot/FMP/PM combinations; and it has investigated the influence of FMP/slot opening width/height on cogging torque.

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