Jiabei Zhu

This paper investigates the voltage harmonics of dual-armature flux-switching permanent magnet (DA-FSPM) machines under load condition, with particular emphasis on the influence of stator and rotor armature reactions. Firstly, the mechanisms of the generation of even and fractional order coil voltage harmonics are investigated. It reveals that the alternate-SP-wound winding, alternate-RT-wound winding, stator winding distribution factor smaller than 1, and rotor winding distribution factor smaller than 1 cause asymmetrical armature reaction flux distributions in the DA-FSPM machines, thus additional harmonics are generated in the stator and rotor coil voltages under load condition. Furthermore, the elimination of even and fractional order harmonics in phase voltages are realized by means of selecting proper numbers of SP and RT and changing the stator and rotor coil connections. It shows that the torque ripple of the machines are reduced thanks to the reduction of voltage harmonics.

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.

This article presents a novel doubly fed doubly salient permanent magnet machine (DFDSPMM) with armature windings wound around stator and rotor teeth. Compared with the conventional doubly salient permanent magnet machine (DSPMM), this machine locates an extra winding in the rotor slots as armature winding to fully use its rotor slot space, thus leading to an increase in the output torque. The structure and operational principle of the proposed machine are analyzed at first. Then, the feasible stator/rotor-pole number combinations are discussed. Furthermore, the electromagnetic characteristics of the investigated machines are predicted based on the 2-D finite element (FE) analysis. It shows that higher torque density and lower cogging torque can be achieved by the proposed DFDSPMMs with improved stator/rotor-pole number combinations. Moreover, the proposed DFDSPMMs are compared against a surface-mounted permanent magnet machine (SPMM) to reveal comprehensive performance. Finally, the prototype is built and tested to validate the 2-D FE predictions.

The design rules of winding configurations and stator-pole/rotor-tooth (SP/RT) number combinations of doubly-fed flux-switching permanent magnet (DF-FSPM) machines are investigated in this paper based on coil electromotive force (EMF) vectors. The relationships between the components of stator and rotor coil-EMF vector diagrams are unveiled at first, including the numbers of stator and rotor phases, and the numbers of stator and rotor spokes. Then, the SP/RT number combinations are derived considering feasible stator/rotor phase number combinations and different winding configurations. The SP/RT number combinations are optimized considering the winding factors, magnetic field harmonics, unbalanced magnetic forces and machine diameter. It is shown that both of the stator and rotor pitch factors increase when the SP and RT numbers get closer. Furthermore, the influence of winding configurations and SP/RT number combinations on electromagnetic performances of DF-FSPM machines are analyzed by finite-element method. Finally, the analysis results are validated by experiment.

In this paper, a novel dual-armature (DA) flux reversal permanent magnet (PM) machine with halbach array magnets in the stator slot opening is proposed, which is abbreviated as DA-Halbach machine. Besides the stator armature windings, another set of windings is added in the rotor slots to further enhance torque performance via fully utilizing the rotor space. The influences of major geometric parameters on torque performance are investigated. Both DA-Halbach machine and conventional Halbach machine are optimized with the goal of maximum torque under the same copper loss using finite element (FE) method. The electromagnetic performance of two optimized machines are compared, the results show that the proposed DA-Halbach has larger torque and smaller torque ripple than conventional Halbach machine. When compared with surface-mounted PM machines, the proposed DA-Halbach machine still show better torque performance.

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.

Three lumped-parameter magnetic circuit (LMC) models of dual-armature flux-switching permanent magnet (DA-FSPM) machines are proposed and compared in this paper. Firstly, the characteristics of the magnetic flux fields produced by the PM, stator armature reaction and rotor armature reaction flux sources are analyzed, with particular attention paid to the air-gap and slot leakage flux paths. Based on the former analyses, three LMC models are developed, which consider the air-gap and slot leakage permeances in different ways. The electromagnetic performances of the DA-FSPM machines are predicted by the three LMC models and validated by finite-element method, including the flux linkage, average torque, inductance, and power factor. The model accuracy sensitivity to the geometric parameters, copper loss allocation, electric loading, stator pole/rotor tooth number combinations, power level and conductor distributions are analyzed. It shows that appropriate consideration of slot leakage permeance is important to improve the model accuracy.

To enhance the thrust force density and move a part of copper loss from the primary to the secondary of linear switched flux permanent magnet machines (LSFPMMs), this paper proposes a novel kind of doubly-fed LSFPMMs (DFLSFPMMs) by adding another set of armature winding on the secondary of LSFPMMs. The design and working principles of the new winding are analyzed first. It is found that the optimal coil pitch depends on the primary structure. Then, the parameters of DFLSFPMMs with U-core, C-core, E-core, and multi-tooth primary structures are globally optimized, and their electromagnetic performances are investigated by 2D finite element method. The result shows that the average thrust force of U-core DFLSFPMM is 30% higher than that of conventional LSFPMM counterpart, and it is also 23%-29% higher than those of DFLSFPMMs with other three primary structures. Besides, the U-core machine with tubular structure is analyzed for the potential application of electromagnetic shock absorbers, which shows the U-core DFLSFPMM has 10% higher peak-to-peak damping force than linear spoken-type PM machine. Finally, a prototype of U-core DFLSFPMM is manufactured and tested to validate the analysis.

In this paper, a novel doubly-fed flux-switching permanent magnet (DF-FSPM) machine is proposed, whose armature windings are wound on both stator poles and rotor teeth. Different from the conventional FSPM machine in which the armature windings are only located in the stator, the rotor slot area is fully utilized in the DF-FSPM machine to improve the electrical loadings and thus the torque density. Moreover, it has potential of fault-tolerant operation, since it comprises two sets of armature windings which can work individually. The topology and operating principle of the machine is introduced with reference to a 12-stator-pole/10-rotor-tooth DF-FSPM machine. The electromagnetic performances of the optimized DF-FSPM machine and its FSPM counterpart machine are compared, including the induced voltage, inductances, torque capability, flux weakening capability, efficiency and power factor. It shows that the DF-FSPM machine can exhibit about 46.5% higher torque density than the FSPM machine, while its torque production per magnet volume is also improved by about 39.6%. In addition, the efficiency and power factor of DF-FSPM machine are higher than those of the FSPM machine. Finally, experimental validation is conducted on a prototype machine.