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Purpose The purpose of this paper is to present an improved winding function theory (IWFT) for performance analysis of surface mounted permanent magnet (SMPM) motors, which can precisely and simultaneously consider the impacts of stator slotting, the winding distribution, the magnetic flux density within PMs because of the armature reaction, the PM magnetization angle and the magnetic saturation,. Design/methodology/approach To obtain this improved analytical model, the conformal mappings (CMs) are introduced to calculate the relative complex permeance of slotted air-gap, which is used to obtain the function of slotted air-gap length. The equivalent magnetizing current model is used to extract the equivalent winding function for each PM pole. For retaining the basic assumption of WFT, the magnetic saturation is also considered by a proper increase in the air-gap length in the front of the stator teeth. Findings A new hybrid analytical model (HAM) based on WFT is presented in this paper, which can simultaneously and accurately consider the effects of slotting, the magnetic saturation, the variation of PM operating point and the winding distribution. In fact, IWFT removes all the drawbacks of the conventional WFT. Moreover, IWFT is more user-friendly and faster than other analytical and numerical techniques. Practical implications The obtained HAM can be used for design, optimization and fault diagnosis in electric machines. Originality/value This paper presents a new HAM for accurate modeling the SMPM motors, which includes different considerations of electromagnetic modeling. This new HAM can also be used for modeling the other electric motors.

Purpose The purpose of this paper is to present a new optimal design for integral slot permanent magnet synchronous motors (PMSMs) to shape the air-gap magnetic field in sinusoidal and to reduce the cogging torque, simultaneously. Design/methodology/approach For obtaining this new optimal design, the influence of different magnetizations of permanent magnets (PMs), including radial, parallel and halbach magnetization is investigated on the performance of one typical PMSM by using the conformal mapping (CM) method. To reduce the cogging torque even more, the technique of slot opening shift is also implemented on the stator slots of analyzed PMSM without reduction in the main performance, including the air-gap magnetic field, the average torque and back-electromotive force (back-EMF). Findings Finally, an optimal configuration including the Hat-type magnet poles with halbach magnetization on the rotor and shifted slot openings on the stator is obtained through the CM method, which shows the main reduction in cogging torque and the harmonic content of air-gap magnetic field. Practical implications The obtained optimal design is completely practical and is validated by comparing with the corresponding results obtained through finite element method. Originality/value This paper presents a new optimal design for integral slot PMSMs, which can include different design considerations, such as the reduction of cogging torque and the total harmonic distortion of air-gap magnetic field by using the CM method.

An enhanced analytical technique based on winding function theory (WFT) is developed in this paper, which can be used for accurate electromagnetic modeling of the induction motors. The enhanced winding function theory (EWFT) acts based on the calculation of inductance matrix of stator and rotor windings while accurately consider the air-gap length function and the magnetic saturation in iron parts, simultaneously. By using the conformal mappings (CMs), a modified air-gap length function is presented for a typical wound rotor induction motor (WRIM), which considers the slot effect on flux tubes in slotted air-gap. The finite element method (FEM) is used to confirm the accuracy of air-gap length function obtained through EWFT. Compared to conventional WFT, EWFT is also redefined to consider the magnetic saturation by using the equivalent virtual winding functions. In real, the magneto motive force (MMF) drops in iron parts of stator and rotor obtained through magnetic equivalent circuit (MEC) are replaced with a virtual winding. In this paper, by using EWFT, a 3-D lookup table is prepared in advance for elements of inductance matrix and their derivative, and it is then used to model the startup and steady-state conditions of WRIM under different load torques. To confirm the accuracy of EWFT, the some corresponding results of EWFT, FEM, and experiment setup are finally compared.