This paper presents an analytical model for the prediction of the performance in a spoke-type permanent magnet synchronous in-wheel motor with trapezoid magnet accounting for tooth saturation. The impact of magnet shape on modeling is considered. To match the standard boundary conditions, the trapezoid magnet is simplified to sector magnets. According to the invariance principle of the magnetic field created by magnet, the dimension of the sector magnet is calculated with lumped magnetic circuit model. Then the motor is divided into six subdomains, i.e., shaft, inner sector magnet, outer sector magnet, rotor slot, air-gap, and stator slot. Based on the boundary conditions, the magnetic field, back-EMF, and torque are obtained by solving the Poisson's and Laplace's equations. The effect of tooth saturation is considered. The finite element method and experiments are employed to validate the accuracy of the analytical model. In addition, the proposed method can also be used to evaluate the performance of the spoke-type motor with any irregular magnet.

This article investigates the water jacket and slot optimization of a water-cooling permanent magnet synchronous in-wheel motor. The optimization consists of the improvements of the water jacket heat dissipation and slot heat dissipation. In order to reduce the temperature difference between the water and water jacket wall, the impact of the water jacket configuration parameters and shapes are theoretically studied. According to the researches, the method for the water jacket optimization is proposed. A slot thermal model is established to optimize the thermal behavior in slots. The variations of the thermal performances with impregnation materials and slot configuration parameters are analyzed. On the basis of the analysis, this article presents a method for the thermal optimization. The validity of the method is supported by the finite element analysis, computational fluid dynamics and experiments.

Interior permanent magnet (IPM) motors are widely used in electric vehicles (EVs), benefiting from the excellent advantages of a more rational use of energy. For further improvement of energy utilization, this paper presents an analytical method of d- and q-axis inductance calculation for IPM motors with V-shaped rotor in no-load condition. A lumped parameter magnetic circuit model (LPMCM) is adopted to investigate the saturation and nonlinearity of the bridge. Taking into account the influence of magnetic field distribution on inductance, the winding function theory (WFT) is employed to accurately calculate the armature reaction airgap magnetic field and d- and q-axis inductances. The validity of the analytical technique is verified by the finite element method (FEM).

This paper presents an analytical approach for the prediction of no-load stator iron losses in spoke-type permanent-magnet synchronous machines. The influence of bridge saturation is considered. According to the permeability distribution, the bridge is equivalent to fan-shaped saturation region with constant permeability. The magnetic equivalent circuit and iterative method are used to calculate the permeability. The motor is divided into six regions, i.e., shaft, inner saturation region, magnet, outer saturation region, air-gap, and slot. The air-gap magnetic field distribution is first calculated on the basis of Poisson's and Laplace's equations. Then, according to the flux paths, the stator core is divided into tooth and yoke. The magnetic densities of the tooth and yoke are obtained on the basis of the continuity of magnetic flux. Finally, the Bertotti model is employed to calculate the stator iron losses. The validity of the proposed method is verified by the finite element method.

High power density outer-rotor motors commonly use water or oil cooling. A reasonable thermal design for outer-rotor air-cooling motors can effectively enhance the power density without the fluid circulating device. Research on the heat dissipation mechanism of an outer-rotor air-cooling motor can provide guidelines for the selection of the suitable cooling mode and the design of the cooling structure. This study investigates the temperature field of the motor through computational fluid dynamics (CFD) and presents a method to overcome the difficulties in building an accurate temperature field model. The proposed method mainly includes two aspects: a new method for calculating the equivalent thermal conductivity (ETC) of the air-gap in the laminar state and an equivalent treatment to the thermal circuit that comprises a hub, shaft, and bearings. Using an outer-rotor air-cooling in-wheel motor as an example, the temperature field of this motor is calculated numerically using the proposed method; the results are experimentally verified. The heat transfer rate (HTR) of each cooling path is obtained using the numerical results and analytic formulas. The influences of the structural parameters on temperature increases and the HTR of each cooling path are analyzed. Thereafter, the overload capability of the motor is analyzed in various overload conditions.

Accurate and timely fault diagnosis of the rotating rectifier in Wound-Rotor Synchronous Starter-Generator (WRSSG) plays an important role for improving the reliability of the WRSSG system. By analyzing the geometric features of the rotor current trajectory of the main exciter (ME) under health and different fault conditions of the rotating rectifier, a fault diagnosis method for the rotating rectifier based on geometric features of ME rotor current trajectory is proposed in this paper. In this method, ME rotor currents are estimated first, and then the center distance, center angle and length-width ratio of the ME rotor current trajectory are calculated and used to detect fault occurrence, locate the faulty diode, and identify the fault type for the rotating rectifier, respectively. Experimental results verified the feasibility and effectiveness of the proposed fault diagnosis method.