This paper reviews the current state of the art of condition monitoring and fault diagnosis techniques for permanent magnet (PM) machines. It also takes into account the past research on this subject as appropriate. The discussion in the paper includes issues related to common abnormalities and specific faults in permanent magnet machines and drives, such as magnet damage and demagnetization, rotor eccentricity, unbalanced magnetic pull, open and short-circuit windings, and switch faults. In this paper, a detailed review is present on the sources of these faults, their analytical model and fault detection tools. Finally, an integrated methodology for condition monitoring of PM machines is discussed.

Torque ripple reduction has been one of the main consideration in the optimal design of traction motors such as permanent magnet assisted synchronous reluctance motors (PMa-SynRMs). Several design techniques including optimal slot/ pole combination, stator slot and rotor magnet skewing, shape optimization of rotor flux barriers have been studied intensively to reduce the torque pulsations in the internal rotor reluctance motors. However, internal rotor reluctance motors involve power train complexity and space constraints in the traction application. On the other hand, outer rotor motors can be designed optimally to eliminate these drawbacks and in addition, produce higher power density. In such outer rotor reluctance motor designs, torque ripple plays crucial role as the in-wheel motor is under duress of consistent rotational forces. Furthermore, optimization of outer rotor in-wheel motors needs to be thoroughly investigated to reduce the torque ripple and to generate higher torque density. In this study, a novel rotor shape optimization based on design of notches and rotor flux barrier is presented. Detailed optimization process in adjunct to analytical and simulation results comparison is presented. Finally, optimal designs are fabricated and tests are conducted on the 3.7kW prototypes to validate the proposed design-optimization theory.

This article proposes a two-layer overlapping winding–based three-phase wireless vehicle charging system with a coil span of 180°. This coil structure offers higher coupling and balance inductance matrices between the transmitter and receiver and improves system efficiency. The system performance improvement has been validated through detailed analysis and simulation results and compared with the benchmark for the same electrical parameters, air gap, and coil volume. Finite element analysis–based simulation results were presented for a 7.7-kW wireless power transfer (WPT) over a 200-mm air gap. An experimental prototype of the proposed system is developed operating at the resonant frequency of 86 kHz with a 200-mm air gap between the coils to validate the design. Both the simulation and experimental results showed a significant increase in efficiency and coupling compared to the conventional WPT systems.

Miniaturized and power-efficient ULF/VLF (0.330 kHz) transmitters are desirable for underground and undersea wireless communications. Transmitters based on rotating permanently-polarized dipoles are promising for such applications. This paper proposes a power-efficient data modulation scheme for such mechanical transmitters based on continuous-frequency FSK (CF-FSK). Theoretical analysis and simulations show that 8-ary CF-FSK is optimal since it minimizes average mechanical torque for a given bit rate. Model predictive control (MPC) of a permanent magnet (PM) motor is proposed for robust implementation of the data modulation scheme. Preliminary results from an experimental prototype are also presented.

The prediction of the maximum operating temperature in electric machines is very important to ensure that the machine can produce the required power safely. Accurate thermal modeling is required to predict the heat transfer coefficient (HTC) of walls between coolant and heat sources and estimate the temperature in the machine. Analytical calculation of HTC is difficult for sophisticated geometric bodies since the dimensionless correlations are only available for simple geometries. To reduce the effort required to develop a thermal model of the cooling system of an electric machine, a two-way hybrid multiphysics approach using finite-element analysis (FEA) and computational fluid dynamics (CFD) to determine the HTC and evaluate the thermal performance of a liquid-cooled electric machine is presented in this article. In this study, a 60-kW switched reluctance machine (SRM) is used as an example model to evaluate its thermal performance. In the hybrid multiphysics approach, using the HTC estimated by CFD and heat generation in the machine as the inputs, the FEA is used to determine the maximum steady-state temperature in the machine. An analytical approach is also implemented to determine the HTC of the example SRM to correlate with the HTC obtained using a hybrid approach. The analytical HTC is used in FEA to obtain the temperature distribution in the machine. The temperature obtained from hybrid and analytical approaches is compared. The SRM considered in this study is built and tested for different operating points. The machine is tested for a long time to record the steady-state temperature at different operating points. Results obtained from the hybrid approach are validated with the experimental temperature data.

An axial flux permanent magnet (AFPM) motor can be considered one of the optimal motor designs due to its higher torque density and compact sizing. The majority of the AFPM models to date adopted surface mounted and spoke type rotor designs for various applications. However, these designs provide poor protection for the magnets. On the other hand, magnets in an AFPM can be placed inside well-designed flux barriers to guard against harsh conditions. This paper describes the design, optimization and prototype development of a double stator single rotor (DSSR) axial flux interior permanent magnet (AFIPM) motor with a novel “H” shaped flux barrier. At first, a preliminary design of the AFIPM with the flux barrier has been developed based on requirements and design equations. A multi-stage optimization method including Taguchi orthogonal array, multivariate regression analysis and the genetic algorithm has been used to calculate the optimal design parameters of the motor. Detailed electromagnetic finite element simulations have been carried out to compare the performance of the optimized model with the baseline design. Finally, a prototype of AFPIM has been developed and experimental results have been verified with simulation data.