This article investigates the influence of design parameters on average torque and compares the electromagnetic performances of novel dual-armature flux-switching permanent magnet (DA-FSPM) machines with different stator core shapes. Firstly, the topology of novel E- and C-core DA-FSPM machines are proposed and their operating principles are introduced. Secondly, the influence of design parameters on average torque of U-, E- and C-core DA-FSPM machines are analyzed in detail, including the stator to rotor copper loss ratio, split ratio, magnet arc, stator tooth arc, stator yoke thickness, rotor tooth arc and rotor yoke thickness. Then, the key parameters of the machines are sequentially optimized to maximize the average torque. It shows that the optimal parameters of the DA-FSPM machines are no longer the same as their FSPM counterpart machines. Furthermore, the electromagnetic performances of the optimized DA-FSPM machines and their FSPM counterpart machines are compared, including the phase back-EMF, electromagnetic torque, overload capability, inductances, power factor, efficiency, and unbalanced magnetic force. Finally, the finite-element analyses are validated on two prototype machines.

Due to additional armature windings on the secondary, dual-armature linear switched flux permanent magnet machines (DALSFPMMs) exhibit higher force densities than conventional LSFPMMs. Nevertheless, the existing DALSFPMMs suffer from larger secondary phase numbers because of the prime secondary pole numbers. This article proposes more optional primary/secondary pole number combinations with fewer phase numbers for DALSFPMMs. The machine topology is introduced first, followed by the analysis of phase numbers, which indicates the DALSFPMMs with 8/9 primary/secondary poles (8p/9s) and 9p/8s have fewer phase numbers and need fewer power electronic devices. Then, the operation principle of DALSFPMM is analyzed from the perspective of air-gap field. After that, the electromagnetic performances of four DALSFPMMs with 8p/9s, 9p/8s, 6p/7s, and 6p/5s are investigated by 2-D finite element method, showing the 8p/9s and 9p/8s machines have higher average thrust forces, lower thrust force ripples, and higher thrust force to permanent magnet (PM) volume ratios than the 6p/7s and 6p/5s counterparts. Finally, a prototype machine is manufactured for the experimental validation.

In this paper, the mathematical model of a novel 12-stator-pole/10-rotor-tooth doubly-fed flux-switching permanent magnet (DF-FSPM) machine employing 3-phase stator winding and 5-phase rotor winding is established and analyzed. Firstly, the stator and rotor winding inductance waveforms are analyzed in stator reference frame and modeled as the functions of rotor position considering major harmonic contents. Then, the inductances are transformed from the stator reference frame into the rotor reference frame using two Park transformation matrices, all of which become constants after the transformation. Thereafter, the voltage equation, power equation, torque equation are derived step by step. It shows that the magnetic coupling between stator and rotor windings causes the phase voltages to be affected by both stator and rotor currents. However, the reluctance torque and the torque produced by the magnetic coupling between stator and rotor windings are negligible. Further, the flux weakening capability of the machine is predicted from the voltage and torque equations. The power factors are analytically calculated and compared with the finite-element analysis, which indicates that both the stator and rotor of DF-FSPM machine exhibit high power factors. Finally, experimental validation is carried out on a prototype machine.

It has been proved that dual-armature permanent magnet (PM) machines have higher power density than conventional PM machines under the same copper loss. However, the thermal conditions of these machines are different. This paper makes a fair comparison between a dual-armature linear switched flux PM machine (DALSFPMM) and a linear surface-mounted PM machine (LSPMM) by considering both electromagnetic performances and thermal conditions. First, the topologies of two machines and platform are introduced. Then, the 2D and 3D finite element (FE) models are employed for the electromagnetic and thermal analyses, respectively. During the machine optimization, the thermal analysis is used to determine the copper loss under the fixed machine dimensions, while the electromagnet analysis is used to optimize the machine dimensions under the fixed copper loss. After iterations, two machines are optimized and their performances are compared. Under the limitations of 80 maximum PM temperature and 120 maximum winding temperature, the DALSFPMM can exhibit 38% higher thrust force density for the continuous duty and up to 43% higher thrust force density for the short-time duty. Finally, a prototype machine of DALSFPMM is tested to validate the analyses.

Electrically-excited flux-switching machines are advantageous in simple and reliable structure, good speed control performance, low cost, etc., so they have arouse wide concerns from new energy field. However, they have much lower torque density/thrust density compared with the same type PM machines. To overcome this challenge, electromagnetic-thermal coupled analysis is carried out with respect to water-cooled electrically-excited flux-switching linear machines (EEFSLM). The simulation results indicate that the conventional fixed copper loss method (FCLM) is no longer suitable for high thrust density design, since it is unable to consider the strong coupling between the electromagnetic and thermal performance. Hence, a multi-step electromagnetic-thermal joint optimisation method is proposed, which first ensures the consistency between the electromagnetic and thermal modelling and then considers the effect of different field/armature coil sizes. By using the proposed joint optimisation method, it is found that the combination of relatively large size of field coil and relatively low field copper loss is favourable for achieving high thrust force for the current EEFSLM design. Moreover, the thrust force is raised by 13-15% compared with using the FCLM. The electromagnetic and thermal performance of the EEFSLM is validated by the prototype test.