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 paper proposes a novel dual-permanent-magnet-excited (DPME) machine. It employs two sets of permanent magnets (PMs). One is on the rotor, the other is on the stator with PM arrays. When compared with the existing DPME machines, not all of the PMs are located in the slots formed by the iron teeth. Specifically, the radially magnetized PMs in the arrays are located under the short iron teeth, while the tangentially magnetized PMs are located in the slots formed by the long stator iron teeth and the radially magnetized PMs. Each long stator iron tooth is sandwiched by two tangentially magnetized PMs with opposite directions, thus resulting in the flux strengthening effect. The simulation analysis indicates that the proposed machine can offer large back EMF with low THD and large torque density with low torque ripple when compared with Machine I from a literature. Meanwhile, by comparison, the proposed machine has great potential in improving the power factor and efficiency.

The dual-permanent-magnet-excited (DPME) machine employs permanent magnets (PMs) both on the stator and the rotor. It relies on the bi-directional field modulation effect (BFME) to achieve stable electromechanical energy conversion. Therefore, this new type of machine is capable of offering much higher torque capability than its traditional counterparts. This paper is devoted to investigating the optimum design method for improving the BFME of DPME machines, so as to further improve their produced electromagnetic torques. Response surface methodology is engaged to investigate the impacts of shape factors of the stator and rotor slots on the torque capability of the DPME machine, and the fitted models are built up by using both the finite element method (FEM) and the least-squares method. After that, the optimum shape factors are obtained from the fitted models. The results estimated by using both two-dimensional (2D)-FEM and three-dimensional (3D)-FEM demonstrate that the pull-out torque of the optimum case is 24.5% larger than that of the initial case, while the usage of PM material of the optimum case is 8.9% less than that of the initial case.

This paper presents a novel transverse flux permanent magnet disk generator (TFPMDG) for wind power generation. The main features of its structure are the modular H-shaped stator cores and two simple rotor disks. What is different from the structures introduced in the references is that each H-shaped stator core is formed by two T-shaped iron cores and a permanent magnet (PM) rather than a complete H-shaped core, which makes the manufacturing simpler and easier. Each rotor disk consists of a rotor holder and several rotor bars, resulting in high robustness and reliability. Moreover, two circular coils in the H-shaped stator cores together with the stator disk are sandwiched by the two rotor disks, which improves the utilization of PMs. In this paper, the proposed TFPMDG is investigated in detail. Firstly, the structure and operating principle are introduced. Then, the magnetic circuit method is used to analyze the TFPMDG. Next, the three-dimensional (3D) finite element method (FEM) is employed to compute the magnetic field distribution and EMF at no load. According to the calculation result, the other three TFPMDGs with different shapes of rotor cores are proposed and analyzed for better back EMF, and then a generator with good performance is selected for load analysis. Finally, a prototype is fabricated and tested, and the simulated results are compared with the measured ones, which proves the rationality of the simulated results.

In this paper, a novel electric vehicle powertrain system is proposed. In the system, a coaxial magnetic gear (CMG), an electromagnetic clutch, a lock, and two electric machines (EMs) are adopted to achieve the power-split by controlling the states of the clutch and the lock, which enables electric vehicles (EVs) to work in four operation modes. The configuration, power flow paths and operation modes are depicted in detail. A dynamic model is established to help determine the parameters and build simulation models. The simple control strategy is adopted to achieve flexible power-splits. How to determine the relevant parameters to meet the drive requirements in the powertrain system is also elaborated. A dynamic simulation using MATLAB/Simulink is performed to take into account the control strategy and New European Drive Cycle. Finally, the simulation results demonstrate, in theory, the rationality of the determined parameters and the feasibility of the operation modes as well as the control strategy.

This paper proposes a dual-stator high-temperature-superconducting modular linear vernier motor (DS-HTS-MLVM), suitable for long stroke applications. The dual stators are two pure slotted-cores, and staggered by half the stator pole-pitch. The mover adopts a modular structure, installed with HTS excitation windings and copper armature windings. The cryostats for HTS windings also adopt a modular structure. In space, the HTS windings and the copper windings are perpendicular to each other, and in different slots. The main merits of the proposed motor are that: 1) the staggered stators with simple structure help to significantly suppress force ripple; 2) the distribution of the two sets of windings can eliminate the conflict of slot space; 3) the modular mover, and the modular cryostats for HTS windings reduce the installation difficulty; 4) the excitation field and air-gap flux can be flexibly adjusted by controlling the DC. In this paper, the structure and the working principle of the proposed motor are elaborated. With the help of finite element method, the electromagnetic performance of the proposed motor is analyzed, and compared to a DS-HTS-MLVM with two stators aligned. The results show that the proposed motor can significantly improve the thrust force density and power density and suppress the force ripple.