Search

This article takes 12-slot/10-pole axial flux permanent magnet (PM) synchronous machine (AFPMSM) with fractional-slot concentrated windings and yokeless and armature (YASA) topology as the research object. Winding magnetomotive force (MMF) of three-phase double-layer layout is analyzed by three kinds of methods, which are star diagram method, winding function method, and holographic spectrum method. The analysis results of finite-element method (FEM) show that the three methods are effective and consistent in analyzing winding MMF. Comparative analysis of iron loss density and B–H magnetizing curves of four typical iron materials are studied. B–H hysteresis loops of silicon steel sheet and soft magnetic composite are measured by magnetizing and measuring equipment to validate iron core per unit mass. The three-dimensional FEM is used for analyzing eddy-current loss in PMs considering radial segmentation. Finally, an AFPMSM prototype is manufactured adopting YASA topology and segmented PM. Load experiments show that solid–liquid coupling computational fluid dynamics model can precisely predict temperature distribution of AFPMSM. Improved cooling jacket is beneficial to afford large current load.

Multiphase machines have been attracting more and more attentions in high-reliability-required applications due to their inherent fault-tolerant capability. Postfault control strategies with-standing open-circuit faults (OCFs) for several multiphase machine types, like five-phase, symmetrical six-phase (S6) and asymmetrical six-phase (A6) machines, have been widely investigated in recent literatures. However, fault-tolerant control for symmetrical dual three-phase (D3) machines have rarely been studied so far. To fill the gap, this paper addresses key issues in postfault decoupling modeling and field orient control (FOC) for the dual three-phase surface-mounted permanent magnet synchronous machine (SPMSM) with isolated neutrals under single-phase OCF. To do so, a postfault decoupling model with reduced-order transformation is established for D3 machines. Postfault current references are reconfigured with two main-stream criteria: minimum-loss (ML) and maximum-torque (MT). Furthermore, third harmonic flux linkage/back-EMF are taken into account in modeling and control, since it causes third harmonic currents and hence torque ripples under single-phase OCF. Proportional-resonant controllers are employed to decrease the third harmonic currents and torque pulsations. The validity of the postfault control strategies is proved by experiments.

This paper proposes a fault-tolerant control strategy of the open-winding inverter for dc-biased vernier reluctance machines (dc-biased VRMs), aiming to maintain the output capability after the open-circuit fault occurs in the inverter switches. DC-biased VRMs are with integrated winding current for both dc component for field excitation and ac component for torque generation. The torque generation is not associated with the current direction, making the full-bridge inverter be divided into two groups of devices. The proposed fault-tolerant control strategy is based on the regular full-bridge inverter for each open winding and can control the motor in the fault-tolerant mode with one group of devices. When an open-circuit fault of a device appears in the normal mode, the controller will switch to the fault-tolerant mode. After a short transient period, the motor will be able to work. Moreover, in the fault-tolerant mode, a pulsewidth modulation driving method is proposed to reduce the current ripple. The proposed method does not require any additional components, and the reliability of the drive control system with the open-winding inverter is improved. Experimental results verify the validity and feasibility of the proposed fault-tolerant control strategy.

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.

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.

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 distorted back electromotive force (EMF) waveforms of dc-biased vernier reluctance machines result in stator current distortion, torque ripple, and efficiency reduction. For the purpose of eliminating the harmonic currents and optimizing the phase current, a new optimal current control strategy is proposed by utilization of accurate fundamental and harmonic voltage equations. Each harmonic component is decoupled in the multilevel synchronous rotating coordinate. The interactions between the multiple harmonic currents are avoided, and it assures a strong robustness. The harmonic currents can be suppressed significantly both in steady-state and dynamic operation, and it has a positive effect on the efficiency and torque ripple. Furthermore, a modified maximum torque per ampere curve considering inductance nonlinearity is achieved by adjusting the dc–ac current ratio under different phase currents, aiming to maximize the output capacity. Finally, the effectiveness of the proposed optimal current control strategy is validated experimentally for a prototype machine.

The effects of multi-phase and multi-layer windings of the 12-slots 10-poles surface-mounted permanent magnet synchronous machines (SPMSMs) on eddy current losses in permanent magnets (PMs) are mainly investigated using the 3-D finite element analysis in this paper. Eddy current losses in PMs considering its axial segmentation are also analyzed. It is demonstrated that dual three-phase four-layer (DTP-FL) winding layout has the minimum value of eddy current losses in PMs, when segmentation number $N = 4$ . It is because DTP-FL winding has smaller magnitude of high-order magnetomotive force harmonics relative to other four winding layouts. The average torque and torque ripple changing with multi-phase, multi-layer, and axial segmentation are also studied. Finally, the no-load and load experiment platform for an axial flux integrated-starter generator with DTP-FL winding and radial segmented PM are established in order to validate the proposed method under power generation mode.

The recent novel dc-biased sinusoidal current reluctance machines (dc-biased VRMs) adopt a doubly salient structure and concentrated windings, which is similar to that of switched reluctance machines (SRMs). The special point is that the phase current is in the form of an ac component superimposed with a dc component. Some literary works show that these machines would have better performance than the existing SRMs and variable flux reluctance machines. In this paper, the slot/pole combinations and winding configurations of the dc-biased VRMs are deeply investigated. First, relationships among slots/poles are given based on the operation principles. Then, several feasible slot combinations are obtained, and the electromagnetic performances including magnetizing inductance, virtual back electromotive force, torque quality, and losses are compared by the finite element analysis. Finally, the correctness of the proposed analysis is validated by the experiment on two 12/10 prototypes.

This paper presents a comparative study of harmonic current suppression control strategies for dc-biased vernier reluctance machines (dc-biased-VRMs). The back electromotive force waveforms of dc-biased-VRMs contain low-order harmonics. It leads to harmonic currents in phase windings. To eliminate the low-order harmonic currents, two types of representative architectures, namely closed-loop current control with proportional integral and resonant regulators and specific order harmonics compensation algorithm in multilevel rotating reference frame, are theoretically analyzed. The performance of the two architectures is compared in terms of accuracy, complexity, and dynamic performance for harmonic current suppression. The experimental results obtained are presented. It verifies that the two strategies have their specific advantages.

This paper addresses the design and investigation of an improved torque density dc-biased Vernier reluctance machine (dc-biased-VRM), which is characterized by salient rotor structure, and merely one set of concentrated windings in stator. First, a 12-stator slot, 10-rotor slot dc-biased-VRM is designed. Then by analyzing the magnetic flux distribution with finite-element analysis, it is found that the flux always doesn’t flow across half of the stator teeth. Therefore, these teeth are removed and a novel 6/10 dc-biased-VRM with 20% higher torque density is obtained. Besides, by optimizing the stator/rotor tooth width combination and tooth shape, the torque ripple is lowered. Finally, a prototype is manufactured and experimental results show good agreement that is observed between the simulation and test data for the proposed motor.

DC-biased sinusoidal current vernier reluctance machines (dc-biased VRMs) have 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, low vibration and noise due to smooth current, compared with switched reluctance machines, and robust rotor structure. Besides, its achievable high slot fill factor can improve the torque density further. In this paper, based on the flux modulation principles, the torque production mechanism of dc-biased VRMs is analyzed, and two slot combinations of 12/8 and 12/10 are proposed. First, the machine topology and inverter main circuit are illustrated. Second, the torque production mechanism is explained. Furthermore, the inductance characteristic, optimal current configuration for maximum torque and lowest torque ripple are analyzed theoretically and by the finite-element analysis. Finally, one prototype was designed and built, and the proposed analysis is validated by the experimental results.

Stator permanent magnet (PM) machines are gaining more research interest in recent decades. Since the permanent magnets (PMs) are moved from the rotor side to the stator side and the salient rotor structure is adopted, it is claimed that the stator permanent magnet machines exhibit several promising features, such as simple and robust rotor, and good ability of heat dissipation as the main losses are located in the stator. On the other hand, to improve the shortcomings of the inherent limited magnetic field adjustment ability, and the low efficiency and power factor of stator dc current excited machines, hybrid excitation PM machines with additional field windings are proposed. However, the complexity of the machine structure is increased inevitably. At present, it is found that both the stator PM and the stator dc current excited Vernier machines operate with the flux modulation principle, and generally, the armature windings of the stator PM machines are fed with pure sinusoidal current. In this paper, a novel hybrid excitation stator PM Vernier machine is analyzed. In addition to the features of the salient rotor structure, stator located PMs, and concentrated armature windings, the novelty of this machine is dc-biased sinusoidal phase current, which contains an ac component and a dc component. The fundamental theories of stator PM machines fed with dc-biased current are researched, operation principle and slot/pole combination is concluded, and the optimal current configuration is studied theoretically and by finite element analysis. Finally, a prototype was designed and manufactured; the experimental tests were done to validate the proposed analysis.

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 the heat dissipation; 2) the rotor is salient structure without PMs and windings, which ensures the reliability of high-speed operation; 3) the nonoverlapping concentrated winding shortens the end-connection, and improves the torque density, 4) only half of the stator teeth possess PMs, and the total amount of PMs are decreased; and 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 electromotive force, torque, etc. are analyzed with finite element analysis. 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 the existing pure sinusoidal phase current, higher torque density can be obtained with dc-biased phase current under constant stator copper loss.

© 1965-2012 IEEE. This paper introduces a temperature-dependent hysteresis model based on a vectorial elemental operator with temperature-sensitive spontaneous magnetization and biaxial anisotropy for the soft ferrites. Detailed analysis of the temperature-dependent magnetic properties of one elemental operator has been presented thereafter. With the help of the proposed vector elemental operator and the 2-D Gaussian distribution function, the temperature-dependent magnetic hysteresis of soft ferrites can be simulated. This model is validated by the substantial agreement between the simulated and measured major hysteresis loops of a soft ferrite sample Siemens 4C65 at different temperatures with slight acceptable error.

Flux modulated machine (FMM) comprises three parts: a conventional stator with armature winding, a rotor with permanent magnet, and iron flux modulation pole. Thanks to the inherent magnetic gearing effect, FMMs have been gaining more attention for their features of high torque density. So far, the windings of existing FMMs are fed with pure sinusoidal current. In this paper, to further improve the torque density using the magnetic gear principle, dc-biased sinusoidal current is innovatively injected into the armature coils which are arranged in a specific way, and the electromagnetic performance is analyzed by the finite element analysis. The results show that the electromagnetic torque contains not only the preexisting 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 with the proposed dc-biased current, the torque density is improved under the constant copper loss compared with the existing pure sinusoidal current. Besides, the flux adjustment ability is greatly enhanced since the exciting field can be easily adjusted by the injected dc current.

Stator dc field winding excited vernier reluctance machines are increasingly attracting research interest recently due to their low cost and highly reliable rotor structure. In this paper, the design of these machines is studied systematically using both theoretical equations and finite element analysis (FEA). First, the general structures of these machines and their operation principles are discussed. Second, based on the operation principle, the back electromotive force, torque, and power factor expressions are deduced in terms of the geometrical variables. Several key design parameters are defined, including stator/rotor slot/pole combinations, air gap, split ratio, field/armature coil turn ratio, and stator/rotor tooth arc combination. Third, the deduced theoretical expressions are verified by the FEA. Finally, a prototype is designed and tested to verify the analysis 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.

In this paper, a novel vernier reluctance fully superconducting (FSC) low-speed direct-drive synchronous generator for a wind power application is proposed. The proposed superconducting (SC) generator is with an external rotor, and both the SC armature and SC dc field windings are in the inner stationary stator. Thus, compared with the existing FSC synchronous generators (FSCSGs), the slip ring is removed, and the cryostat and related refrigerate systems are stationary and greatly simplified. In addition, both the field and armature windings are single tooth-wound concentrated windings with very short end-windings. Compared with the regular FSCSGs, the usage of the SC material is greatly reduced in this proposed topology, as with the total cost. Furthermore, the torque ripple is much lower than that in a regular FSCSG. All these features are evaluated by the finite-element simulations.

Stator dc winding excited Vernier reluctance machines (DC-VRMs) are one novel kind of Vernier reluctance machines, and have doubly salient structure and additional dc field windings in their stators to generate the exciting field. These machines advantages include a wide speed range, due to the flexible exciting field by the dc winding and a robust rotor structure without permanent magnets or windings. In this paper, the nature and principles of DC-VRMs are first illustrated theoretically with winding function and harmonic theories. First, by considering the permeance modulation function, the equations and harmonics of the exciting field are obtained. Next, based on these results, the stator/rotor pole combinations and armature winding configuration methods are proposed. Additionally, the expressions for the self-inductance, mutual inductance, the back electromotive force (back-EMF) of armature windings are summarized with the winding function theories. Also, the effects of permeance, field, and armature winding harmonics on inductance harmonics are analyzed. The equation for electromagnetic torque is also given, and the design parameters that may influence the machine's torque are provided. Finally, the inductances and torque in synchronous reference frame are analyzed. All the analytical results are validated by finite element analyses and some experimental results are also given to validate the theoretical analysis.

The Cobb-Douglas production function is often used to estimate the benefit of water use and the value of water; however, this is an incorrect application. A typical example of the inapplicability is that a negative output elasticity of water resources may be reached when empirical data is collected from the United States, Japan and the city of Beijing in China, where economic growth still increases when the quantity of water use decreases. It is counter-factual that the benefit of water use or the value of water resources are negatively associated with economic production as estimated by the Cobb-Douglas production function. In the case of a positive output elasticity of water resources, the Cobb-Douglas production function cannot be used either. The main reason is that the elasticity of water resources, as an input factor, reflects only part of its total contribution to economic output. In other words, the contribution of water resources to total economic growth, to a great extent, are embodied in total factor productivity, which refers to the portion of output that cannot be explained by the amount of water resources input in the Cobb-Douglas production function. For example, many technological and socio-economic inputs such as the investment on water saving technologies and the optimization of water use structure, surely embody the value of water and account for total economic output, yet these factors are not reflected by the economic output elasticity of water resources in the Cobb-Douglas production function.

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.

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.