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Multiple torque component single air gap magnetless machine is a kind of novel machine, which exists outstanding fault tolerance. Due to the dual armature winding on both the stator and rotor, it can produce four torque components and can work under different operation situations. However, there are a few researches studying the current distribution on stator and rotor armature windings. This paper proposes a method to settle the problem of stator and rotor current distribution by applying the MTPA control strategy. Firstly, the topology and operation principle of the machine is introduced, then the mathematical model is given. After that, the MTPA control strategy is deduced and analyzed.

This paper presents an adaptive position observer using normalized position error input in wide-speed sensorless interior permanent magnet synchronous motors (IPMSM) drives. The normalized position error observers of saliency-and model-based field orientations method are established, for which the position information can be unified extracted in wide-speed operation. However, this process introduces extra parameter factors and wide-speed operation especially in regeneration mode worsens the dynamic performance of drives. To realize smooth switch between two different drives and fast dynamic response, concept of equivalent control is incorporated into the observer design. The position error dynamic is extended to a third-order model, and the super-twisting algorithm is adopted to estimate high-order total disturbance. The key step is to introduce the corrective terms and the filtered equivalent control term, which forces the error dynamics to approach a finite-time converge second-order differentiator. A rigorous equivalent control stability analysis is set forth, and a convergence analysis of observer states is elaborated. Effective simulation results are included to verify the feasibility of the proposed scheme.

In recent years, the fault-tolerant performance of electric machine systems has received much attention in the fields of electric vehicles, military industries, aerospace. This paper focuses on modeling, and field orientation control (FOC) for a novel dual stator/rotor PM and winding flux modulated PM machine (FMPM). The remarkable characteristic of the machine is that both the stator and rotor have PMs and windings. The particular structure enables the machine to generate multiple torque components, improving torque density and fault tolerance. Firstly, the machine's topology and multiple torque components are illustrated, then the mathematical model of the machine and control system based on the FOC method are investigated. Finally, simulation is carried out in MATLAB, and the simulation results verify the feasibility of the proposed method.

The driving electric machine of high-power flywheel energy storage system (FESS) has the characteristics of high fundamental frequency and low inductance, which lead to high current harmonic content and increases the loss of FESS. To suppress the current harmonics, a compound control scheme is proposed for an innovative hybrid converter in this paper. The mathematical model of the hybrid converter is analyzed and divided into two parts: main voltage source converter (MVSC) and filtering voltage source converter (FVSC). According to the characteristics of MVSC and FVSC in output power and switching frequency, two different regular sampling strategies are described and applied. On this basis, the exact MVSC model in discrete time-domain is established, and the current controller with complex vector decoupling is designed. Similarly, a current controller with feedback decoupling is designed for FVSC in the continuous time-domain. Both the current controllers have excellent robustness and dynamic response ability. Finally, the proposed control strategy in this paper is verified by simulation results.

Hybrid distribution transformer (HDT) has high controllability for the grid current and load voltage, and it is useful for constructing the future active distribution network. To overcome the limitations of the existing HDT control scheme with PI regulators and improve the performance of high-order harmonic suppression of the existing HDT with L-Type converters, a control scheme with quasi-proportional-resonant (PR) regulator is proposed for HDT constructed with LCL-Type converters in this paper. This control scheme is developed based on the single-phase dynamic model of the improved HDT in static coordinate and, hence, has simple block diagram. The dynamic model is constructed according to the equivalent circuit of HDT. In this dynamic model, the grid current and load voltage coupled weakly and, hence, the quasi-PR regulators for the grid current and load voltage control are designed separately. Simulation results validate the effectiveness of the proposed PR control scheme of HDT.

In this paper, an ultra-high torque density flux modulated permanent magnet machine (FMPM) topology is elaborately constructed. Its main structural features are that both stator and rotor parts consist of PMs and armature windings, so that a single air gap and simple structure is kept. Meanwhile, the rotor space is fully utilized. What’s more, both the PMs can interact with both the windings, and produce four torque components, and the output torque on the shaft is the superposition of these four torque components. Consequently, extremely high torque is expected. This paper firstly introduces the topology and the main inverter circuit of the machine. Then taking the proposed machine as an example, the basic operation principle and slot/pole combination equation are illustrated. Finally, the electromagnetic performance including flux density, back electromotive force (EMF), torque quality and power factor are analyzed by FEA and the fault tolerance of a set of windings fault is verified.

This paper proposes a drive topology and control strategy for a two-phase DC biased vernier reluctance machine (DCB-VRM) with non-overlapping windings. By analyzing the operating principle of the newly proposed two-phase DCB-VRM, a novel and low-cost drive topology is proposed; by build the mathematical model of the machine, a novel control strategy is proposed. Since a DC current path needs to be reserved in the DCB-VRM drive topology, more power switching devices are needed in theory. To decrease the total cost, in this paper, the drive topology is greatly simplified by combining DC paths. At the same time, because the number of power switching devices required is greatly reduced, the cost of the overall drive system has also been effectively reduced. For the novel drive topology, this paper proposes a novel control strategy. Through effective control of the machine dq0 axis current, maximum torque output can be achieved while reducing losses. In order to verify the effectiveness of the proposed drive topology and control strategy, a model of drive and control system of the machine was established in MATLAB/Simulink. The results of model simulation verify that the proposed drive topology and control strategy can effectively control the two-phase DCB-VRM.

Fractional slot concentrated winding (FSCW) permanent magnet (PM) machines have been promising candidates for industrial applications and domestic appliances due to their outstanding performance. Based on the magnetic field modulation principle, this paper presents an idea for performance improvement of FSCW consequent pole PM machine (FSCW-CPM) by adding PM in the stator slot opening. In this paper, taking one typical slot/pole pair combination of 12/7 as example, the principle of enhanced flux modulation is illustrated firstly. It reveals that multi-harmonics can contribute to torque generation. After that, the electromagnetic performance, including flux-linkage, back EMF, and torque, etc. are analyzed by finite element analysis (FEA). The results validate that the proposal can improve the performance of FSCW machine effectively due to the enhanced flux modulation principle.

High-performance permanent magnet motors can operate reliably at temperatures of $100^{\mathrm{o}}\mathrm{C}$ or more. In hightemperature environments, the temperature has a great impact on the performance of materials such as permanent magnets, cores, and windings. However, according to the test standard, the magnetic properties of magnetic materials are usually measured at room temperature, ignoring the effect of temperature. To accurately design magnetic devices that are used at high temperatures, it is necessary to understand the behavior of several magnetic materials at high temperatures. The purpose of this paper is to analyze and study the effect of temperature on the characteristics and performance of highspeed permanent magnet motor in high-temperature environments.

This paper proposes a novel high-speed permanent magnet synchronous machine (HSPMSM) topology. The characteristics of the proposed machine are: 1) the stator winding is divided into two parts and each part is connected by the end ring at one end, which is helpful to solve the existing shortage of overlong end length in traditional HSPMSM. 2) the stator of the machine is designed with closed slot, which can greatly weaken the eddy current loss and the cogging torque of the machine. 3) the machine is driven by two separate three phase converter, which can improve the fault tolerance. In this paper, the topology, and the corresponding control system is analyzed firstly. After that the electromagnetic performance, including back electromotive force, cogging torque, torque, etc. are analyzed with finite element analysis (FEA). In addition, the losses, including the stator copper loss, the stator iron loss and the eddy current loss of the permanent magnet and sleeve of the rotor, are calculated by FEA. Finally, the mechanical strength of rotor is also checked. The results show the validity of the topology, and it is useful for the further improvement of torque density for HSPMSM.

The fault-tolerant capability of the electrical machine system in the event of certain faults is critical for application in the fields of aerospace, in-wheel vehicle, etc. This paper analyzes the operation modes and control principle of a novel type of machine with multiple electromagnetic torque components. Firstly, the topology and operation principle of the electrical machine are briefly illustrated, and then the mathematical model, and especially the torque component is introduced. After that the control principle considering the characteristics of multi-torque components is analyzed. Finally, the operation modes of the machine under different working conditions are analyzed.

The high-speed electric machine has been widely used in uninterruptible power supplies, wind power plants, rail transits and hybrid vehicles due to the high power density and fast dynamic response. However, the dynamic characteristics of the current loop will deteriorate with the increase of the speed, and it is difficult for sensorless control methods to operate reliably under low frequency modulation index. Therefore, discrete current regulator and super-twisting sliding mode observer (ST-SMO) are proposed in this paper. The directly discrete model of permanent magnet synchronous machine (PMSM) is analyzed firstly in complex-coefficient. On this basis, using the zero point of the current regulator to eliminate the poles of the controlled object, the discrete current regulator is designed with the compensation of the inherent digital delay in controller. Then, the structural equation of discrete ST-SMO sensorless control method is expounded. In addition, a comparison between discrete ST-SMO and continuous ST-SMO is carried out. Finally, the proposed control strategy in this paper is verified by simulation results.

This paper proposes a DC-link voltage controller based on fast super-twisting sliding mode control (ST-SMC) algorithm with linear extended state observer (LESO) and a full-order Luenberger observer based on direct discrete PMSM model for high speed flywheel energy storage system (FESS). The mathematical model of flywheel and the dynamic equation of DC-link during discharge are described. On this basis, a DClink controller combining fast ST-SMC and LESO is proposed. The traditional PI, fast ST-SMC and the proposed algorithm for DC-link are compared in many aspects. For the high speed sensorless control of FESS, the direct discrete complex vector PMSM model is derived firstly. Then the Luenberger observer considering the digital delay in controller is obtained. In addition, the proposed full-order Luenberger observer is compared with the traditional Luenberger based on first-order Euler. Finally, the proposed control strategies in this paper are verified by simulation results.

High-speed permanent magnet synchronous machine (HSPMSM) has been widely used in high speed direct-drive applications due to its high power density and high efficiency. However, the low inductance of the HSPMSM under the condition of low carrier ratio of the motor-drive system, especially in medium and high power systems, results in high current harmonics. This paper proposes a hybrid pulse width modulation (PWM) strategy in full speed range of HSPMSM system based on a hybrid utilization of the space vector PWM (SVPWM) method and the selective harmonic elimination PWM (SHEPWM) method, in addition to having a RLC harmonic filter. The operating principle of the SHEPWM is analyzed firstly, and the structure and working principle of the system are expounded. Then, a comparison between the SHEPWM and SVPWM is carried out considering the current harmonics. Furthermore, the SHEPWM and the RLC filter are combined to achieve a better overall performance. Finally, the dynamic switching technology under different PWM methods is investigated to achieve smooth transition, and the proposed control strategy in this paper is verified by simulation results.

A hybrid sensorless control system for the ironless flywheel machine based on I-F startup strategy and improved full-order sliding mode observer (FSMO) is proposed in this paper. I-F startup method is adopted for the low-speed sensorless control, and the improved FSMO is appropriate for the medium and high speed. In this paper, the principle and dynamic process of I-F startup is analyzed firstly. Then, the FSMO and sinusoidal switching function are carried out using stator current and back electromotive force as state variables, and the estimated rotor position and speed are got through the phase-locked loop. Compared with the traditional sliding mode observer, this method has the advantages of reducing phase delay, weakening system chattering and improving the accuracy of position calculation. Furthermore, the dynamic switching technology is studied and the smooth transition between the two sensorless control methods is achieved. Finally, the effectiveness of the proposed method is verified.

With the continuous requirement for improvement of international motor efficiency standards, the research and exploitation of motor with higher efficiency standards has become an important development trend in the motor industry. Synchronous reluctance machines (SynRMs) with simple rotor construction, no need of permanent magnets and similar price compared to the induction motors are considered to be another promising type of motor in addition to permanent magnet motors that can achieve IE4 efficiency standards. This paper describes the design and optimization of SynRM with different number of poles to achieve IE4 efficiency level. First, the sample data was obtained by the finite-element analysis (FEA), then in order to establish the relationship between the design parameters, saturation effect and the motor performance, such as torque, torque ripple, etc., the optimization model of the SynRMs was established by using extreme learning machine (ELM). Finally, a genetic algorithm (GA) was used to search the best optimization performances and geometrical parameters. FEA proves the effectiveness and validity of the proposed method.

The demand for highly efficient electric machines has been expanded in recent decade due to increase of energy consumption and the improvement of international standards for high efficiency machines. Although the rare-earth permanent magnet machines usually exhibit high performance, rare-earth resources are limited and their cost is high. In this case, this paper studies and compares the performance and cost of 2.2 kW copper-rotor induction machine (CR-IM), synchronous reluctance machine (SynRM), and PM-assisted synchronous reluctance machine (PMASynRM) achieving IE4 efficiency level. A finite-element method (FEM) is used to validate the performance of three machines. The results show that SynRM can achieve IE4 efficiency level with the lowest cost, but the power factor is a big challenge, PMASynRM has the best performance and a competitive cost advantage compared to CR-IM.

In this article, a novel electric machine having permanent magnets (PMs) in both stator and rotor parts, and fed with dc biased phase current is proposed. The innovative characteristic of the proposed machine is that it contains multiple field excitation sources including stator PM, rotor PM. and dc component in the phase current. Thus, the exciting field can be greatly strengthened. What is more, the exciting field is flexible and adjustable thanks to the variable dc component. Therefore, the proposed machine is expected to exhibit high torque density, wide constant power operation range. This article first illustrates the basic operation principle, slot/pole combination equation, and the topology. Then, performance of six machines with different slot/pole combination is analyzed. After that, effects of several key design parameters on machine performance are researched theoretically and by finite-element method and genetic algorithm. And neural network is applied to verify the correctness of torque and torque ripple. Finally, the electromagnetic performance including flux density, back electromotive force, torque quality of an optimized machine is illustrated.

Dual three-phase permanent magnet synchronous machines (PMSMs) are widely used in the applications which require high power density and high reliability. Inductance calculation for these dual three-phase windings of this machine type is a key issue for further performance analysis and controller design. This paper attempt to use the winding function approach to establish an analytical model for computing the inductance of the dual three-phase PMSM type with symmetrical winding configuration. With this method, a complete analytical expression of self and mutual inductances between phases has been obtained. Finally, simulation and experimental results have been implemented to verify the accuracy of calculation results.

This paper deals with the analysis of two interior permanent magnet (IPM) machines with different winding type for electric vehicle (EV) application. The performances, such as torque, cogging torque, power factor, efficiency, flux weakening capacity, losses, radial force and vibration of 12-slot 10-pole IPM machine with FSCW and 24-slot 10-pole IPM machine with the coil-pitch of two slot-pitches winding is detailed discussed by finite-element analysis (FEA) method.

This paper takes 12-slot/10-pole axial flux permanent magnet synchronous machine (AFPMSM) with fractional-slot-concentrated-windings (FSCW) as the research object, comparative analysis of iron loss density and B-H magnetizing curves of four typical iron materials are studied. In addition, measured BH hysteresis loops of silicon steel and soft magnetic composite (SMC) are obtained by magnetizing and measuring equipment to validate iron core per mass. The 3D finite element method (FEM) is used for eddy-current loss calculation in PMs considering radial segmentation. Finally, an AFPMSM prototype of the 12-slots/10-poles combination is manufactured adopting the yokeless-and-segmented armature (YASA) topologies and segmented PM rotor. Tests shows that 12-slots/10-poles combination can significantly reduce the core and PM losses, and improve the power density.

This paper proposes a three-phase four-leg drive for dc-biased sinusoidal current vernier reluctance machine (DC-VRM). By adding an asymmetrical neutral leg to the conventional three-phase inverter, the dc field excitation current can be generated. Compared to the open-winding inverter (conventional drive topology), the three-phase four-leg inverter greatly reduces the number of power devices, and the asymmetrical neutral leg does not have short-circuit straight-through risk. The topology ensures that the stator current can flow in both directions and maximum torque per copper loss can be obtained in DC-VRM. Equivalent carrier-based pulsewidth modulation (PWM) strategy is proposed to produce the dc-biased sinusoidal current and maximize the dc bus utilization. The proposed carrier-based PWM has several different equivalent methods. Compared to the conventional DC-VRM drive, the power loss of the proposed drive with equivalent space vector PWM (SVPWM) can be reduced significantly and can be further reduced by discontinuous PWM minimum (DPWMMIN) in the rated condition. The proposed drive has the characteristics of low cost, high power density, and high efficiency compared to the conventional DC-VRM drive.

In DC-biased sinusoidal current vernier reluctance machines (DC-biased-VRMs), the DC exciting winding and AC armature winding are integrated into one single winding. Therefore, the copper loss can be reduced with torque density increasing, and only one set of power electronic converter is demanded. This paper is to propose a DC-biased-VRMs drive with asymmetrical power electronics devices and corresponding control strategy. In order to make the power dissipation and temperature rise of each devices more balanced, the asymmetrical H-bridge inverter with both higher current capacity devices and lower ones is designed as well as simulated. The proposed asymmetrical H-bridge can reduce the cost of power electronics devices effectively due to the use of lower current capacity IGBTs and diodes without unipolar current constraint. The simulation and experimental results verify that the proposed drive system is feasible for DC-biased-VRMs driving.

This paper introduces a novel linear vernier permanent magnet machine (H-LVPMM) with high force density and low force ripple. The permanent magnets (PMs) on secondary uses Halbach array, which can provide a larger flux density in the air gap than that of the conventional surface-mounted PMs configurations, and the primary is composed of three modules, which are separated by two flux barriers. Moreover, the three-phase winding connections and the length of the two flux barriers are specially designed to minimize the cogging force and the ripple force. In order to show the superiority of the H-LVPMM, a conventional linear vernier permanent magnet machine using surface-mounted PMs (S-LVPMM) is built and compared to the proposed machine in terms of back electromotive force (back-EMF), cogging force, average thrust force, thrust force ripple, etc.

DC-excited vernier reluctance motors are usually fitted into two sets of stator windings: DC current winding for generating magnetic field and armature winding for producing rotating magnetic flux. However, two separated sets of stator windings require larger motor size and complex winding structure. Two sets of power electronics converters are required to drive both the excited and rotational windings. This paper investigates DC-biased sinusoidal current vernier reluctance motors with single stator winding compared with traditional structure. Furthermore, the structure of power electronics inverter for supplying the stator currents with DC-biased component is proposed, due to unipolar direction of current flow. The proposed inverter can reduce the quantity of power electronics devices by 50%. Also, the half-bridge structure of the proposed drive can avoid DC-bus shoot-through failure physically. A prototype of the DC-biased sinusoidal current vernier reluctance motor has been developed together with the proposed drive and controller. Finally, the experimental results verify that the proposed inverter configuration can be effectively applied in DC-Biased sinusoidal current vernier reluctance motor drives.

Recently, a novel hybrid excited vernier permanent magnet machine (HE-VPM) is proposed. The proposed machine is with stator located PMs, and concentrated armature windings. The current waveforms of the armature windings are sinusoidal with DC bias, as the injected DC biased current can weaken or enhance the exciting fields at high/low speed. Due to the characteristics of double salient structure, a massive amount of back-EMF harmonics in phase windings will appear when the machine is operating, and the DC flow path will lead to current waveform distortion in phase windings, result in torque ripple and influence the efficiency of the motor. By analyzing the mathematical equations in dq0-axis, a harmonic current suppression control strategy for HE-VPMs is proposed. The control strategy produces the corresponding voltage compensation in dq-axis, counteract with the back-EMF harmonics to achieve the purpose of eliminating the circulating harmonic current. Finally, the experimental results verified that the proposed control strategy can suppress the harmonic current in phase windings effectively.

This paper propose the stainless retaining cage of the FSCW-SPM servo motors for retaining the PM. Compared to the FSCW-SPM servo motors with normal stainless sleeve, there is low rotor eddy current losses by using the retaining cage. In this paper, the structure strength of the stainless retaining cage is analyzed and proven having the enough reliability.

Recently, stator dc current excited vernier reluctance machines (dc-VRMs) which have concentrated field and armature windings in stator, are gaining more and more research interest due to their features of robustness rotor structure, low cost, and easy heat dissipation. This paper proposes a novel field winding connection for dc-VRMs. Taking the stator/rotor slots of 12/10 machine as an example, the electromagnetic performance including back electromotive force (EMF), pulsating torque, and capability are analyzed using the theoretical and finite element analysis. The results show that compared with the previous machine having the same stator/rotor slots, machine with the proposed field winding connections exhibits a doubling back EMF, and 60% higher torque density.

Flux modulated machines (FMMs) are well known for their features of high torque density. In this paper, the DC currents are innovatively injected into the armature coils which are arranged in a specific way in FMMs, and the electromagnetic performance are analyzed by the finite element analysis (FEA). The results show that the electromagnetic torque contains not only the pre-existing PM torque, but also the additional torque produced by the DC current interacted with the AC armature current. What is more, it is found that the torque is improved under the constant copper loss compared with when fed with regular pure sinusoidal current. Besides, the flux weakening capability is greatly enhanced since the exciting field can be easily adjusted by the injected DC current, therefore, it can be inferred that the constant power speed range is extended.

This paper proposes a novel hybrid excitation vernier permanent magnet machine (HE-VPM). The characteristics of the proposed machine are: 1) The PMs are embedded in the stator teeth, which is helpful for heat dissipation; 2) the rotor is salient structure without PMs and windings, which ensures the reliability of high speed running; 3) The non-overlapping concentrated winding shortens the end-winding, and improves the torque density, 4) Only half of the stator teeth possess PMs, and the total amount of PMs are decreased; 5) The DC current are injected to the armature coils, therefore, the exciting field can be adjusted flexibly. In this paper, the electromagnetic performance, including back-EMF, torque, etc. are analyzed with finite element analysis (FEA). The results show that the proposed machine exhibits flexible field adjustment capability, which may be suitable for applications requiring wide speed range operation. Besides, it is found that, compared with fed with the existing pure sinusoidal phase current, higher torque can be obtained with DC-biased phase current under constant stator copper loss.

This paper proposes a novel vernier permanent magnet (VPM) machine for hybrid electric vehicle (HEV) applications. The main features of the proposed machine are concentrated armature windings with short and non- overlapping end-winding, and the permanent magnets (PMs) are on both sides of rotor and stator. Unlike conventional motors, this machine operates with flux modulation principles, and the electromagnetic torque is produced by the interaction between the armature magneto motive force (MMF) and the exciting fields by stator and rotor PMs. In this paper, the electromagnetic performance is simulated by the finite element analysis (FEA). The results show that the torque density is about 33% higher than an existing interior permanent magnet (IPM) machines.

Stator DC winding Excited Vernier Reluctance Machines (DC-VRMs) are a kind of novel machines, which are investigated more and more owing to absence of expensive permanent magnet material. However, DC-VRMs are found to have large torque ripple if they are not carefully designed. There are a lot of existing methods to reduce the cogging torque in permanent magnet (PM) machines, but the design techniques for DC-VRMs have only been mentioned recently in few papers. In this paper, some new methods are proposed including shifted rotor tooth, stepped rotor skewing with multiple modules, T-shape rotor tooth, various rotor tooth arc, rotor tooth-chamfering, different length of air gap, and these methods are based on the techniques for PM machines to reduce torque ripple. The influence of the proposed methods on torque ripple is examined by using Finite Element Analysis (FEA) and it is found that the torque ripple can be reduced significantly.

In this paper, a novel class of hybrid excitation, stator vernier permanent magnet (VPM) machines (HE-VPM) are proposed. The proposed machines are with salient rotor structure, stator located PMs, and concentrated armature windings. Therefore, the superiority of the proposed machine is robust rotor structure, short and non-overlapping end-winding, and easy heat dissipation. Besides, a novel DC-biased sinusoidal current, which contains an alternating current (AC) component and a direct current (DC) component, is applied, with this novel current, a novel hybrid excited VPM machines without additional field windings are obtained. The simulation results shows that the proposed machines exhibit higher torque density, power factor, and efficiency, Also, the constant power operation range is broadened, as the injected DC biased current can weaken or enhance the exciting fields at high/low speed. Finally, a prototype has been designed and under built, and the corresponding experiments will be added later.

The recent novel DC biased sinusoidal current reluctance machines (DC-biased VRMs) are similar to switched reluctance machines (SRMs) in terms of structure, as they both adopt the doubly salient structure and concentrated windings. However, the special characteristic of DC-biased VRMs is that their phase currents have both DC current and AC current. Therefore, it can be inferred that the vibration and noise can be much smaller than SRMs as the phase current waveform is smooth. Besides, compared with variable flux reluctance machines with specialized field windings, DC-biased VRMs exhibit better performance such as fewer copper loss and higher torque density. In this paper, the stator/rotor slot combinations and armature winding configurations with different pole pairs of the DC-biased VRMs are deeply investigated. Firstly, relationships among stator/rotor slots and armature winding pole pairs are given based on the working principles. Then, several feasible stator/rotor slot combinations are obtained, and the electromagnetic performances are compared by the finite element analysis (FEA). The results show that the 8-rotor-slot, 5 armature pole pair machine exhibits highest torque in rated load, but with highest torque density, the 10-rotor-slot, 4-armature pole pair machine shows highest torque in over load condition, and the 12/11 and 12/13 machine presents the minimum pulsation torque.

DC-biased sinusoidal current vernier reluctance machines (DC-biased-VRMs) are with a doubly salient structure, and their phase currents contain an alternating current (AC) component and a direct current (DC) component. Hence, their main features are one set of concentrated windings compared with variable flux reluctance machines (VFRMs), low vibration and noise due to smooth current, compared with switched reluctance machines (SRMs), and robust rotor structure. Besides, its achievable high slot fill factor can improve the torque density further. However, the existing DC-biased VRMs, whose stator/rotor slots of 6/4 and 6/8 have high torque ripple. In this paper, based on the flux modulation principles, the torque production mechanism of DC-biased VRMs are analyzed and two slot combinations of 12/8 and 12/10 are proposed. Firstly, the machine topology and inverter main circuit is illustrated. Secondly, the stator armature pole pairs/rotor pole relationship and pole ratio is given. Furthermore, the inductance, optimal current configuration for maximum torque and lowest torque ripple are theoretically analyzed and by the finite element analysis (FEA). Finally, one prototype has been designed and under built, and the experimental results will be then given.

In this paper, a novel vernier reluctance fully superconducting synchronous generator (FSCSG) with low temperature superconductors (LTS) for wind power application is proposed. The feature of this superconducting generator is an external rotor structure, and both the superconducting armature windings and DC field windings are in the inner stationary stator. Thus, compared with the existing FSCSFGs, the cryostat and related refrigerate system of the proposed generator is greatly simplified. Besides, the results shows that the torque density is about 37% higher and the torque ripple is as low as 6.9% without any optimization and skewed.

This paper analyzes the conventional windings, detached windings and alternative windings for vernier reluctance dual-stator axial flux machines. The connection of winding configurations is firstly given, followed by a comprehensive comparison in aspects of no load flux linkage, cogging torque, rotor unbalanced axial force, torque, torque ripple and iron loss.

Stator wound field synchronous machines (SWFSMs) are gaining more and more research and application interest recently due to the absence of expensive rare earth magnet materials. These machines are characterized by a doubly salient structure, and both the DC field winding and the three phase armature windings are located in the stator. In this paper, taking the basic structure of stator DC excited vernier reluctance machine, which is one type of SWFSM, the design of SWFSMs are studied in detail semi-analytically, by finite element analysis (FEA), and also validated by experiment. First, the effects of stator/rotor slot combinations on performances, including cogging torque, torque and torque ripple, voltage fluctuation of the DC winding are analyzed and compared. Then, the back-EMF, torque and power factor expressions in terms of the geometrical variables are proposed. Also, a 12-stator-slot, 11-rotor-slot machine as an example, the design parameters, including the split ratio, the air gap length, the proportion of the armature and field coil turns in one stator slot, and the stator/rotor tooth arc combination are optimized. The optimization results show that these design parameters have a various influence on electromagnetic performance, and the designers should select the design parameters comprehensively.

Stator DC-excited vernier reluctance machines (DC-VRMs) are vernier reluctance machines equiped with additional DC field winding in stator to generate the exciting field, a rotating field similar to synchronous reluctance machines (SynRMs). This paper compares the electromagnetic performance of two non-PM reluctacne machines including DC-VRMs and SynRMs. First, the basic operation principle of DC-VRMs and SynRMs are briefly reviewed. Then, four machine models, two DC-VRMs and two SynRMs are designed and optimized for comparison. For a fair comparison, the phase current, current density, slot fill factor and dimensions including the stator outer diameter, air gap and stack length are designed the same. The electromagnetic performance including flux density, torque quality, overload capacity, power factor and losses are compared in detail.

The novel vernier reluctance machines with DC field winding in stator (DC-VRMs) have the advantages of wide speed range due to the flexible exciting field by DC winding, robust rotor structure thanks to no PMs or windings on rotor similar to doubly salient machines[1-3]. In this digest, the effect of ratio of rotor poles to stator armature winding poles on the electromagnetic performance, such as back-EMF, torque and torque ripple and so on are researched based on six machines, which stator/rotor slot number are 12/7, 12/10, 12/11, 12/14, 12/16, 12/17, respectively and the corresponding pole ratio are 7/1, 10/4, 11/5, 14/4, 16/2 and 17/1, respectively. It is found that, the average torque is mainly determined by the ratio of rotor poles to stator armature winding poles in a certain region. For torque ripple, it is mainly affected by the least common multiple (LCM) of the number of stator and rotor slots. For example, 12/17 exhibits the lowest (1.4%) while the 12/16 is largest (80%).