The rotor eccentricity fault will cause the electric vehicle (EV) drive machine to generate unbalanced magnetic pull (UMP) and torque fluctuation. It may induce more complex rotor dynamics behavior and endanger the safe and reliable operation of the drive system. In this article, three spoke-type interior permanent magnet synchronous machines (IPMSMs) with different armature winding structures, which are integer-slot double-layer distributed winding, fractional-slot double-layer concentrated winding, and fractional-slot four-layer concentrated winding with star–delta (Y– $\Delta$ ) connection, are introduced. The armature magnetomotive force (MMF) analytical models of the three IPMSMs are built. Also, the air-gap permeability is analyzed when static eccentricity, dynamic eccentricity, and mixed eccentricity faults occur in IPMSMs. Furthermore, electromagnetic characteristics of the three IPMSMs under different rotor eccentricity faults are studied. Effects of static eccentricity and dynamic eccentricity faults on cogging torque, back electromotive force (EMF), radial electromagnetic force, electromagnetic torque, loss, and efficiency of the IPMSMs with three different winding structures are compared and analyzed. Research shows that the IPMSMs with integer-slot distributed winding and fractional-slot concentrated winding have different performances under rotor eccentricity faults.

Electromagnetic torque model is built in this paper for permanent-magnet synchronous machine (PMSM) with non-sinusoidal back electromotive force (back-EMF) and current. Electromagnetic torque is divided into four parts depending on the different combinations of fundamental and harmonic component. Effects of current harmonic order, amplitude and initial angle on average torque and torque ripple are investigated based on the mathematic model. Desired harmonic parameters are obtained from the analysis, in order to suppress the torque ripple as much as possible. Further, a method for reducing the 5^th and 7^th harmonic components of torque ripple is proposed, according to the characteristics of back-EMF harmonic distribution. The proposed method is greatly simplified and more feasible by only injecting 5^th and 7^th harmonic currents. The theoretical analysis validity has been proved by finite element (FE) simulation, and the FE results show that torque ripple would be more effectively reduced by injecting proper harmonic current than weakening it merely.

Two kind of nonuniform slot distribution models, the unit machine shift model (Model 1) and the single slot shift model (Model 2), are proposed for reducing cogging torque of surface-mounted permanent magnet(SPM) machines. Further, based on exact subdomain model and Maxwell stress tensor, an analytical model is further built for calculating cogging torque in SPM machines with nonuniformly distributed stator slots. Its accuracy and feasibility have been validated by finite element (FE) method. With the analytical model, effects of slot shift angle on cogging torque are investigated for an 8-pole/12-slot SPM machine. Meanwhile, coupling relationships between shift angle and other design parameters (slot/pole number, pole arc coefficient and slot opening) are analyzed. In addition, influences of slot shift on back-EMF and electromagnetic torque are also studied. Conclusions are drawn from the analysis and indicate that Model 1 is much better than Model 2 in improving the performances of SPM machine.

The design and analysis of a novel salient-pole surface-mounted permanent magnet synchronous machine (SSPMSM) are presented in this paper for wide-speed range applications. In this machine, iron teeth are placed in the d-axis on the surface of rotor core to increase armature inductance and enhance the effect of d-axis armature reaction. But torque ripple is also increased since the rotor teeth increase the saliency of the machine. So segmented Halbach magnetization is applied to reduce the electromagnetic torque ripple. In order to investigate the characteristics of SSPMSM, four finite element (FE) models with different rotor cores and magnetizations are built. Flux-weakening/enhancing characteristics, no-load characteristics and load characteristics are obtained and compared. The results show that SSPMSM has better magnetic field adjustment ability than traditional surface-mounted permanent magnet synchronous machine (SPMSM).

Medium-voltage cables in hydropower plants are typically arranged in multi-circuit configurations to ensure reliability, yet their exposure to harsh operational conditions accelerates insulation degradation and increases partial discharge risks. Traditional fault localization methods, such as the traveling wave method using wavelet transform to process fault signals, suffer from wavefront distortion due to inter-line reflections and noise interference in multi-circuit systems, because wavelet-based techniques are limited by preset basis functions and environmental noise. To address these challenges, a fault localization method for multi-circuit parallel cables based on the Teager–Kaiser Energy Operator (TKEO) is proposed in this paper. First, the fault signal is decoupled using Clarke transformation to suppress common-mode interference, obtaining the α component. Subsequently, the α component is subjected to wavelet transform to obtain the high-frequency components, which are then optimized using the TKEO. The TKEO is applied to optimize the wavelet-transformed signal, enhancing transient energy variations to precisely identify the arrival time of the fault wavefront at measurement points, thereby enabling accurate fault localization. The results of the four types of fault experiments indicate that the use of the TKEO to optimize the wavelet transform of the traveling wave method improved the accuracy of fault localization.