With development of electrical machines, traditional machine theory can no longer explain the operation principles of some new type machines, such as vernier machine, stator PM machine, etc. The principle of flux-modulation (FM) provides an important direction for development of machine theory. This study overviews the development of the FM machine regarding its principle and topology. According to the studies on FM effect of different types of electrical machines, it can be found that FM principle is universal in electrical machines. However, the researches of FM principle are still limited to some specific machines at present and it leads to the fragmentation of theory. A new general air-gap FM theory is introduced and it can be expected to be the unified theory for electrical machines. To verify the correctness of the new theory, some electrical machines, including induction machine and non-salient pole machine, are analyzed by the general air-gap FM theory. In addition, the design and engineering application of FM machine and theory is analyzed. To verify the inherent unity of electrical machine, the topology evolutions of FM machine are also discussed. Based on the new general air-gap FM theory, the innovative methods of topology can be summarized while the development prospects of FM machine are subsequently discussed.

The multiphase receiver for more steady output is proposed in this paper. The conventional power supply rail with multipole such as I-type has a main drawback: the induced voltage of the double-D coil of receiver has a sinusoidal fluctuation. The multiphase receivers are proposed to solve the problem. The fluctuation factor, effective value of induced voltage and mutual inductance, cost and loss of different numbers of phase in different connection modes are analyzed and compared. The applicable conditions of different types are given. The structural size of single-phase coil is optimized to achieve larger coupling coefficient. The influence of distance between phases on fluctuation factor and induced voltage are calculated and the design principle of the distance between phases is determined. Design guideline is proposed including the constraints of installation environment and the distribution of different phases. The structural size of single-phase coil and the distance between phases are optimized to improve the coupling coefficient and reduce cost, loss and voltage level of resonator. A four-phase receiver of 10kW DWC system is designed and constructed. In the dynamic 10kW experiment, the fluctuation factor is reduced to 0.146 from 0.3 of two-phase receiver and 1.0 of single-phase receiver.

This paper investigates and compares the torque-generating capabilities and electromagnetic performance of advanced non-overlapping winding induction machines (AIM), conventional induction machines (CIM), and interior-permanent magnet (IPM) machines for electric vehicle (EV) applications. All investigated machines are designed based on the specifications of the Toyota Prius 2010 IPM machine. The steady-state and flux-weakening performance characteristics are calculated by employing the 2D finite element method and MatLab, and the obtained results are quantitatively compared. Furthermore, the torque-generating capabilities of three machines are investigated for different electric loadings, and the machine having the highest torque-generating capability is determined as AIM. Moreover, the major parameters affecting the torque-generating capability, such as magnetic saturation and magnet demagnetization, are examined in depth.

Coaxial Magnetic gears (CMGs) have attracted increasing attention in recent years. The field modulation effect arising from modulating ring is considered as the reason why CMG can realize torque transmission between its two rotors. However, the magnetic torque interaction among modulating ring and two rotors is rarely investigated. Therefore, the purpose of this paper is to figure out the detailed torque distribution on the modulating ring, which plays a crucial role as the force/torque medium between the inner rotor and the outer rotor. Firstly, the conceptual model, the operating principle, and the practical configurations of CMGs are introduced. Secondly, theoretical derivation of torque distribution on each surface of modulating rings with different connecting bridges is conducted by using Maxwell stress tensor method. The calculation results match very well with those obtained from the traditional "holistic analysis method" which is widely used in previous publications, and this validates our proposed "detailed analysis method". Thirdly, how the connecting bridges affect the torque distribution on modulating rings is presented intuitively. Finally, three CMGs with inner bridge, outer bridge and double bridge, respectively, are built for experimental verification.

This article proposes a straightforward and effective control strategy to reduce the periodic speed ripple of the permanent-magnet synchronous motor. The control strategy can be described as injecting current harmonics whose amplitude and phase can be adjusted automatically to compensate for periodic speed ripple. Compared with the resonant controller with the Tustin transform, the method proposed in the article can track speed ripple frequency without frequency displacement, realizing no steady-state error. Besides, the system stability is analyzed, and the phase compensation scheme is proposed to increase the phase stability. Moreover, the equivalence between the harmonic injection module and the resonant controller has been analyzed, which provides a simple way to understand the phase compensation of the resonant controller. The theoretical analysis and experimental results are presented to verify the feasibility of the proposed harmonic injection method.

In this article, a design of bipolar nonsalient pole (BNSP) transmitter, which originates from motor theory, for high-power EV dynamic wireless power transfer (DWPT) system is proposed. To analyze and evaluate BNSP transmitter in aspect of principle, characteristic, and performance, the existing I-type, S-type, and N-type transmitters in DWPT application are classified as bipolar salient pole (BSP) transmitter, which establishes a reference for comparing. The design parameters and other contrast conditions of BNSP and BSP transmitters are given. Coupling flux and leakage flux of BNSP transmitter are analyzed by comparing the magnetic models and the finite-element models of BNSP and BSP transmitters. Based on the modular design in practical application, the sensitivity of coupling performance to the module gap in BNSP and BSP transmitters is analyzed and compared in simulation. All theoretical results are verified by contrast experiments. The maximum effective mutual inductance of BNSP transmitter is about 31.0% larger than that of BSP transmitter, and the efficiency of the system with output power of 10 kW is 93.5% with BNSP transmitter, about 2.4% higher than that with BSP transmitter. Besides, BNSP transmitter needs 5.9% shorter Litz wire and 53.1% smaller volume of cores, which makes it smaller in size.