The high current ripple and torque ripple are the main drawbacks of the switched reluctance motor (SRM) since the nonlinearity and double saliency, which limits its applications. In order to eliminate the current variation and torque ripple, an optimized pulse width modulation (PWM) control is presented in this paper. The voltage ratio duty is able to be predicted precisely according to the information of the motor running parameter. Based on torque sharing functions (TSFs), the current profile is pre-computed and four regions are defined according to the reference current profiles. The three modes, excitation, demagnetization and freewheeling, are flexibly chosen according to the characteristic of the current profile. It is indicated that it is better than that of conventional PWM modulation in terms of current ripple and the current tracing performance is improved without increasing the switching frequency or changing the hysteresis band. The current ripple is defined as the peak-to-peak value dividing the average value and it is reduced by 40%. A comparison in terms of the torque ripple and copper loss is also carried out: the torque ripple is significantly reduced via the proposed scheme under both magnetic linear and saturation conditions. The torque ripple and copper loss are reduced by about 70% and 12%, respectively. The validity and effectiveness of the proposed control strategy is verified by simulation and experimental results.

Conventionally, the nonadjustable air-gap flux density generated by the permanent magnet (PM) of PM machine would cause large core loss during the standby operation state of flywheel energy storage system (FESS), which would reduce the energy conversion ratio of system. To suppress the no-load core loss, a mechanically modulated PM homopolar inductor machine (MM-PMHIM) is proposed. However, the MM-PMHIM has intrinsic three-dimensional (3-D) flux density distribution, which would be time-consuming to analyze the no-load electromagnetic performance by the finite element method, especially in the initial design stage. Addressing this issue, an analytical method based on magnetic equivalent circuit (MEC) considering the different flux weakening states of the MM-PMHIM is proposed in this article. First, the special topology and operation principle of the MM-PMHIM are analyzed. Second, the MECs of this machine under different flux weakening states are established, and the detailed building processes are presented. Third, several main electromagnetic performance indexes, including flux density distribution, flux linkage, back-electromotive force (back-EMF), etc., are fully analyzed. Finally, the no-load electromagnetic performance of the proposed MM-PMHIM under different flux weakening states is evaluated and the effectiveness of the MEC models are proved by finite-element method (FEM) and prototype test. The result shows that the proposed analytical method can quickly and accurately analyze the no-load performance of the MM-PMHIM.

Cryogenic motors, as one of the key components of submerged liquefied natural gas (LNG) pumps, have gradually attracted the attention of researchers with the vigorous development of LNG industry. In this paper, the design, performance analysis, and experiment of a submerged cryogenic permanent magnet synchronous motor (PMSM) are investigated. Considering the effect of cryogenic temperature on material properties, the cryogenic temperature design method is proposed, and on this basis, an 18.5-kW cryogenic PMSM is designed. Then, the finite-element method is used to analyze the motor performance. The analysis is focused on the comparison of electromagnetic characteristics at two different cryogenic temperatures. A multiphysical field model coupling with electromagnetic, fluid, thermal, and stress is established and simulated, and the analysis results proved the rationality of the design. Finally, a prototype was fabricated and tested, providing measurement results that show a stable operation of the motor, which validated the theoretical design and analysis.

Cogging torque (CT) would cause the vibration and noise of the permanent magnet homopolar inductor machine (PMHIM), which should be suppressed. However, the unipolar air-gap flux density and the dual-segment stator and rotor cores of PMHIM make the characteristics of CT unclear, which leads to a lack of theoretical basis for suppressing the CT. Addressing this issue, the CT of PMHIM is investigated and suppressed. Firstly, the model of CT of PMHIM with integer and fractional slot configurations is developed, and the factors affecting the CT are revealed. Then, the methods for suppressing the CT are proposed based on changing rotor parameters. The influences of different rotor parameters on electromagnetic performance, including back electromagnetic force (EMF), output torque, current and efficiency are fully analyzed. In addition, the characteristics of the proposed method are highlighted by comparing the performance of the method proposed in this paper with the global optimization method in terms of CT suppression. Finally, the theoretical analyses are validated by experiments. The results show that the CT of PMHIM can be effectively suppressed by the proposed method in this work.

For electrified transportation (eTransportation) systems, multi-phase motors can provide higher performance and reliability than three-phase ones, but also bring more challenges in their optimal design and control. In this article, a set of high reliable electric drive system based on dual three-phase permanent magnet synchronous motor (DTP PMSM) is developed for auxiliary systems in eTransportation field. A digital collaborative develop process is proposed with the support of multiple software tools. Design, manufacture, and bench testing stages of the DTP PMSM, the two-level six-phase inverter, and the control algorithm are efficiently incorporated. A prototype of the multi-phase electric drive system is fabricated and tested. Comparison of the simulation analysis and experimental results confirms the effectiveness of the collaborative develop progress. Control algorithms based on dual d-q model and vector space decomposition model are both verified and compared via the bench test. Operation mode switching from six-phase mode to three-phase mode is also realized with the prototype system, verifying its capability in fault-tolerant and potential in efficiency optimizing.

In order to better adapt to the load unbalance in the operation of counter-rotating propeller (CRP), a novel counter-rotating axial-flux hybrid-excitation permanent magnet machine (CR-AFHEPMM) is proposed in this paper, which combines the high torque density of the axial-flux permanent magnet machine (AFPMM) and the flexible flux adjustment of the hybrid excitation machine. The DC field windings are installed near the inner diameter of the SMC stator core with a special structure, enabling reverse adjustment of the air-gap magnetic field on both sides. Unbalanced load operation of two rotors can be realized without increasing the machine volume. Firstly, the structural features and operation principle of the CR-AFHEPMM are presented. Then, the influence of slot-pole combination, permanent magnet (PM) arrangement and key structural parameters on the stable operation, output torque and load unbalance range are studied. Finally, an optimal structure of the Halbach array consequent-pole PM rotor is further proposed and analyzed. The results show that the proposed CR-AFHEPMM is a promising candidate for the application of CRP.