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This article explores enhancing spoke-type flux-intensifying permanent magnet (SFI-PM) motor performance by strategically placing flux barriers (FBs) in the asymmetric rotor. Integrating multi-FBs into the conventional spoke-type PM (CSPM) rotor topology elevates the d-axis inductance ( $L_{d} \gt L_{q}$ ), intensifying flux density and improving output torque while posing challenges like increased cogging torque, torque ripple, and harmonic distortion. An asymmetric rotor design is proposed to mitigate these issues by strategically placing a higher number of FBs along the forward direction (FD) of the spoke magnet axis (q-axis). Analysis reveals that this configuration reduces torque ripple and enhances output torque. A multi-objective genetic algorithm (MOGA) is applied to optimize this asymmetric design considering mechanical constraints. The analyses are validated by manufacturing and testing a 5-kW asymmetric SFI-PM machine with a higher number of FBs along the FD of the spoke magnet axis.

This contribution elucidates the impact of the fillet radius (FR), a geometric feature of rectangular insulated wires not commonly considered, on the partial discharge inception voltage (PDIV) in low-voltage machine turn-to-turn winding insulation. Initial PDIV tests involve edgewise-insulated wire samples with a reference FR. These measurements are performed under constant conditions: 30 °C temperature, 35% relative humidity (RH), and atmospheric pressure (1000 mbar). These tests are carried out under ac 50-Hz excitations, following IEC 60034-18-41 guidelines for inverter-fed motor insulation system qualification. Subsequently, a probabilistic PDIV predictive model is developed based on Schumann’s streamer inception criterion (SCSIC). This expanded model then analyzes and forecasts the impact of the FR on PDIV and its associated dispersion level, within the context of the two-parameter Weibull distribution and the given environmental conditions. Furthermore, a novel method is presented to understand partial discharge (PD) phenomenology and its destructive potential in rectangular insulated wires with varying fillet radii. This approach employs SCSIC-derived streamer inception parameters (SIPs): critical field line length (CFLL), air effective ionization coefficient ( $\alpha _{\text {eff}}$ ), PD inception field ( ${E}_{\text {inc}}$ ), and firing voltage ( ${V}_{\text {firing}}$ ). The developed probabilistic predictive model enables the selection of an optimal FR value, facilitating the creation of a reliable insulation system with maximum PDIV and minimal PD-related damage.

This contribution develops the partial discharge inception voltage (PDIV)-finite-element method (FEM)-based model based on Schumann’s streamer inception criterion (SCSIC) with respect to thermal aging time (TAGT) or the insulation lifetime for the turn-to-turn insulation of coil winding made by rectangular insulated wires. The accelerated thermal aging is performed at 250 °C, which is 50 °C higher than the thermal class, with aging intervals of 156 and 312 h. PDIV measurements are conducted at a constant temperature of 25 °C, 40% relative humidity, and atmospheric pressure (1013 mbar). The measurements are done under ac 50-Hz excitations, following IEC 60034-18-41 guidelines for inverter fed motor insulation system qualification. Furthermore, this study analyzes streamer inception parameters such as critical field line length (CFLL), effective ionization coefficient ( $\alpha _{\text {eff}}{)}$ , partial discharge (PD) inception field ( ${E}_{\text {discharge}}{)}$ , firing voltage ( ${V}_{\text {firing}}{)}$ , and its correlation with PD charge amplitude as a function of TAGT or the insulation lifetime.

Most industrial applications concern output torque, rotor mass, and utilization of rare Earth permanent-magnet (PM) material of electrical machines. Generally, it is challenging to improve these aspects simultaneously. The objective of this article is to propose a novel concentrated-flux-type PM machine with irregular magnets and iron poles (CPMIP). The configuration has following advantages. First, the employment of quasitrapezoid magnets with opposite magnetization direction and large cross-section helps to enhance the flux-focusing effect and thus the torque generation. Second, the quasitriangular iron poles can improve the magnetic self-shielding effect well, and thus the rotor yoke can be removed completely and the rotor mass could be reduced significantly. Third, due to the reduction of PM volume and the improvement of torque output, the PM utilization ratio of electrical machine can be increased greatly. The schematic structure and pole patterns of the proposed electric machine are presented. Subsequently, the equivalent magnet circuit is established to validate the performance improvement of the CPMIP machine. Then, the design improvement with offset iron-pole arc is proposed to suppress torque ripple and balance torque output and PM utilization ratio capability well. Following that, an electrical machine with the irregular magnets and iron poles is designed. Then, the electromagnetic characteristics of the proposed pole designs are compared with those of the electric machines with conventional radial, Halbach, and consequent-pole patterns. Finally, the research prototype is developed, and experiments are conducted to verify the design concept and analysis of CPMIP machine.

For a five-phase permanent magnet synchronous machine (PMSM), the third-order harmonic back EMF is increased by changing the shape of the permanent magnet for increasing average torque in healthy operation. Additionally, in the open-circuit (OC) and short-circuit (SC) faults, the effect of injected third-order harmonic back EMF also needs to be considered. Therefore, this paper proposes a fault-tolerant control method with original transformation matrixes and coefficients reconfiguration in fundamental and third-order harmonic subspaces for both single-phase OC and SC faults. Fault tolerance can be applied by reconfiguring the relative coefficients after an OC or SC fault occurs, depending on the type of fault. Besides, the proposed method aims to optimize the OC fault tolerance strategies and effectively solve the single-phase SC fault, considering the influence in the third-order harmonic back EMF. According to experimental results, the torque fluctuation after applying the proposed method is similar to that in the healthy stage and much lower than that using most fault-tolerant control methods without considering the third-order harmonic back EMF.

The automotive intelligence and electrification require the braking system to cooperate with the controller to achieve regenerative and active braking functions. Hence, the range and driving safety of the electric vehicles are improved. Electromechanical brake (EMB) systems completely abandon the fluid and hydraulic elements and replace the traditional hydraulic braking system with a wire harness and electromechanical parts. The braking torque adjustment is achieved entirely by controlling the four-wheel EMBs. At present, reliability and fault tolerance are the key technical issues associated with EMBs. To eliminate the need of any clamping-force sensor due to its vulnerability and high cost, in this article, a switching extended state observer (SESO) is presented to provide rapid force estimation with higher precision. The substrates of the internal linear and nonlinear structures have been unified into a single form by using an equivalent gain method. The SESO is effective to detect the initial contact between the braking disk and pad by estimating the load torque. It is experimentally verified that the developed force sensorless control strategy is accurate and superior to the existing techniques.