Vernier Machine Research Articles

Design and Analysis of a Permanent Magnet Vernier Machine with Non-Uniform Tooth Distribution

To improve the torque performance of the permanent magnet vernier machine in the direct-drive system for Unmanned Aerial Vehicle (UAV), this paper proposes the topology of non-uniform tooth distribution. This distribution, considering the additional flux harmonics, aims to contribute to torque improvement, whereas the cogging torque also increases at the same time. A phasors method is proposed to solve the issue caused by the non-uniform structure, adjusting the mechanic angle of each tooth reasonably to restrict the cogging torque. In addition, the non-uniform design is illustrated in detail, which includes the method of grouping the teeth, considering the factors of series pole ratio and winding layout. By using the three-dimensional finite element method, torque is significantly increased without additional torque ripple, which satisfies the desired design target.

A Novel Consequent-Pole Modular-Mover Linear Permanent Magnet Vernier Machine for Thrust Ripple and Cost Reduction

Recently, linear permanent magnet vernier machine (LPMVM) is attracting more and more attention due to its high thrust density, high efficiency, and simple structure at low-speed operation, which makes it a preferable solution for direct-drive linear motion applications. In order to further reduce the thrust ripple and the cost of LPMVM, a novel consequent-pole modular-mover LPMVM (CM-LPMVM) is proposed and analyzed in this article. Due to the dual-flux-modulation effect, the proposed CM-LPMVM can exhibit a low thrust ripple (∼3.2% of the average thrust) and high thrust density (∼387 kN/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ) at a low current density of 3 A/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , as well as reduce nearly half of the PM usage at the same time. The performance improvement of the proposed CM-LPMVM is verified by the comparison to a regular modular-mover LPMVMs, using the finite-element method. Finally, three prototypes are built and tested. The experimental results match well with the analytical data, showing the superiority of the proposed CM-LPMVM.

Design and Analysis of an Outer Mover Linear-Rotary Vernier Machine

Design and Analysis of an Outer Mover Linear-Rotary Vernier Machine

Design and Realization of a Hybrid Excited Flux Switching Vernier Machine for Renewable Energy Conversion

This paper presents the design of a hybrid excited flux switching Vernier machine. This machine is designed to serve in renewable energy conversion applications, such as a wind turbine generator, or tidal turbine generator. After introducing this original structure, a design based on finite element models is conducted. The specifications correspond to relatively low power direct drive wind or tidal turbine applications. The rated power is set to 10 kW, with a rated speed of 300 rpm. Mainly the electromagnetic design is presented. Aspects related to the realization of a prototype are also presented, and an experimental study is included.

A Novel DC-Biased Current Dual PM Vernier Machine

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.

Robustness optimization of fault-tolerant permanent magnet vernier machine under multimode operation

<p indent=0mm>To enhance the electromagnetic torque of permanent magnet vernier machine parameters, a multi-objective optimization method considering the parameter uncertainty is proposed under multifault tolerant control modes. The proposed method solves the problem of uncertain parameters, which affects this machine. First, according to different open-circuit conditions under the fault-tolerant control mode, the optimization objectives and constraints are set up. Second, the torque and its ripple under different fault-tolerant operation modes are optimized using a deterministic genetic algorithm. Finally, the robustness of the machine is optimized using the 6<italic>σ</italic> quality optimization method. The results showed that the optimized permanent magnet vernier machine has excellent torque performance under multimode operation and significantly improved robustness.

Analysis and detection of turn‐to‐turn short circuit fault in a permanent magnet Vernier generator based on modified winding function

Operation of Vernier machines is based on flux modulation. They have some advantages including maintaining the rated torque in motor applications and the rated output power in generator applications at low speeds, high torque density and relatively low torque ripple due to their magnetic gear property and fault-tolerance. In recent years, the motor with various topologies has been developed for different applications. Therefore, analysing and monitoring different faults is essential in the design and implementation stages. This study has two main purposes. First, to introduce an accurate frequency index independent of load variations for detecting the turn-to-turn short circuit (TTSC) faults in the stator windings of a permanent magnet Vernier machine. Second, modelling the machine in a healthy condition and in the presence of TTSC faults to investigate its effect on machine performance and output characteristics. An analytical model is presented using the modified winding function theory under the TTSC fault by taking into account the effect of stator slots which enhances the accuracy of the air-gap permeance function estimation. In the process of calculating the fault index, frequency components of the output characteristics of the machine are obtained from the mathematical equations of the magnetic field. It is shown that the proposed indicators are robust against load variations.

Study of the Influence of the Armature Number of Phases on the Electromagnetic Torque Quality in PM Vernier VRM

This paper aims at dimensioning and studying three examples of PM Vernier machines with different number of armature phases to analyze, under the same conditions, the influence of the number of phases on the electromagnetic torque quality. An analytical energy model is first introduced along with the pre-design procedure which leads to a first three phase prototype (VRM_1). The performance of the latter is then studied using analytical approach and numerical modeling based 2 D FEM. Two other prototypes of 5 and 7 phases are sized using the same procedure and constraints as the first machine. Their performances are studied using the same approaches and the electromagnetic torques of the three structures are compared.

Analysis and Design of a Fault-Tolerant Permanent Magnet Vernier Machine With Improved Power Factor

This article aims to analyze and design a fault-tolerant permanent magnet Vernier (FTPMV) machine with improved power factor. Different from the existing FTPMV machine with uniform distributed split-teeth stator, hybrid stator and multiple working harmonics designs are adopted in this proposed machine. With these designs, the proposed machine can obtain not only improved power factor but also higher torque and good fault-tolerant performance. First, the topologies, fault-tolerant design and working principle of the proposed machine are introduced. Then, accurate permeance and equivalent magnetic circuit analytical models are established for investigating the mechanism of power factor improvement. And the influences of some key design parameters on power factor and torque of the proposed machine are analyzed by finite element analysis. Finally, a FTPMV prototype is manufactured and tested to validate the designs and analyses.

Design and Analysis of Fractional Pole-Pair Linear Permanent Magnet Machine

A novel concept of fractional pole-pair linear permanent magnet machine (FP-LPM) has been proposed recently. It is found that using fractional pole-pair number in linear permanent magnet machine(LPM) could effectively reduce slot cogging force as well as back EMF unbalance. Thus thrust ripple is curtailed which improves its thrust quality and enhances its application potential. However, some issues of FP-LPM still remain unsolved, such as phase split, current phase adjustment, plus structure optimization is different from the traditional topology due to extra auxiliary tooth, etc. This paper contributes to giving a detailed designing methodology including winding arrangement, regulations of choosing slot/pole combination and effective end optimization method of FP-LPM. Thus, this paper can give helpful guidance in designing FP-LPM to satisfy different application demands. Finally, an 18slots/29poles fractional pole-pair linear permanent magnet vernier machine (FP-LPMVM) is designed and constructed using the proposed method and the test results verifies the research conclusions.

Design and Analysis of a Dual Airgap Radial Flux Permanent Magnet Vernier Machine with Yokeless Rotor

This paper presents a novel topology of dual airgap radial flux permanent magnet vernier machine (PMVM) in order to obtain a higher torque per magnet volume and similar average torque compared to a conventional PMVM machine. The proposed machine contains two stators and a sandwiched yokeless rotor. The yokeless rotor helps to reduce the magnet volume by providing an effective flux linkage in the stator windings. This effective flux linkage improved the average torque of the proposed machine. The competitiveness of the proposed vernier machine was validated using 2D finite element analysis under the same machine volume as that of conventional vernier machine. Moreover, cogging torque, torque ripples, torque density, losses, and efficiency performances also favored the proposed topology.

Characteristics Analysis of Consequent-Pole Ferrite Magnet Vernier Machine Using Novel Equivalent Magnetic Circuit

This study deals with a consequent-pole (CP) vernier motor with low-cost ferrite magnets. To investigate the magnetic behavior of the CP permanent magnet vernier machine (CP-PMVM) quantitatively, two magnetic equivalent models are newly proposed which are applied to estimate the main and the modulation flux densities in air gap, respectively. Using the proposed models, it is revealed that the CP structure substantially reduces the effective air-gap length, and thus, a CP-PMVM with half number of magnets has much higher modulation flux density than that of a regular surface PM vernier machine (SPMVM). Consequently, the CP-PMVM is expected to able to keep the vernier effect high even with thick ferrite magnets, producing higher back electromotive force (EMF) than the SPMVM does. Moreover, large variation of air-gap length due to thick magnet thickness leads to a considerable advantage of reluctance torque. For a proto-designed CP-ferrite PMVM, the electromagnetic characteristics, such as main and modulation flux densities, back EMF, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> inductances, and torque, have been investigated by using the proposed method as well as finite-element (FE) method. In addition, through the demagnetization analysis, it is proved that the proposed CP-PMVM has certainly enough antidemagnetization capability, whereas an SPMVM with ferrite magnets loses its magnetism. From the analysis results, it is confirmed that the proposed machine with less magnet volume and low-cost ferrite magnets has higher torque compared with its SPM vernier counterpart. Finally, to validate the analytical and numerical analyses, experimental results are provided.

A High Torque Density Claw-Pole Permanent-Magnets Vernier Machine

Permanent magnets vernier (PMV) machine is gaining more and more attention due to its high torque density contributed by multi-orders working harmonics, especially low-pole-pair numbers harmonics. Spoke-array PM machine seems to be a good way to increase the machine working harmonics. But the flux barrier effect is revealed and it explains why the advantages of the spoke-array PMV (SAPMV) machine are not fully used. Thus, its low-pole-pair numbers harmonics could be further enhanced. In this article, a novel structure&#x2014;claw-pole PMV (CPPMV) machine&#x2014;is first proposed and its working principle is investigated. Then, the CPPMV machine is compared with the surface-mounted PMV machine, the SAPMV machine, and the SAPMV machine with alternate flux bridges in terms of their electromagnetic performances using equivalent circuit analysis and FEM. The result shows that claw-pole structure can enhance the magnetic flux modulation effects, which increases the machine torque density. At last, a CPPMV machine prototype is manufactured and tested. Experimental results indicate that it reaches a torque density of 30.5 kNm/<inline-formula> <tex-math notation="LaTeX">$\text{m}^{3}$ </tex-math></inline-formula> and a power factor of 0.84 underrated conditions.

A Hybrid Analytical Model for Permanent Magnet Vernier Machines Considering Saturation Effect

This article proposes a new hybrid analytical model combining subdomain model and equivalent magnetic network for permanent magnet vernier machines, which are easy to get saturated due to the air-gap field modulation effect. The key is representing saturation effect by iterating equivalent surface current as part of interface conditions in the proposed subdomain model. First, five subdomains are divided to calculate magnetic field distribution. The equivalent surface current is utilized as the boundary constraint between subdomains and iron core. Second, the equivalent magnetic network is established based on stator structure, and the fluxes flowing into flux modulation poles are equivalent as the magnetic flux sources. Node magnetic potentials can be achieved with the application of Kirchhoff's law of current. Then, the equivalent surface current is updated for convergence by node magnetic potential to accurately predict saturated performance. Finally, a prototype is manufactured, and the effectiveness of the proposed hybrid model is verified by the finite-element analysis (FEA) and experimental results. The hybrid model combines the subdomain model and the equivalent magnetic network model to complement each other and it is demonstrated to be more efficient than the FEA model while maintaining high accuracy.

Investigation of Line-Start Permanent Magnet Vernier Machine With Different Rotor Topologies

As a new type of flux modulation machine, line-start permanent magnet vernier machine (LSPMVM) has drawn increasingly more attention. Thanks to the rotor starting winding; its self-starting capability can be acquired without applying the inverters. As a result, the system reliability has been improved and cost can be decreased, which is promising for industrial applications, such as pumps and fans. To extend the family of LSPMVMs and select the preferable topologies meeting different requirements, four LSPMVMs, including V-shaped LSPMVM, consequent-pole U-shaped LSPMVM, dual-stator spoke LSPMVM, and consequent-pole surface-mounted permanent magnet (SPM) LSPMVM, have been proposed in this article. The steady-state performance, starting and synchronization capability are comprehensively analyzed and compared, where the regular commercial line-start permanent magnet synchronous machine (LSPMSM) is used as a counterpart. It is found that all the proposed LSPMVMs can acquire the higher torque density. Especially, the V-shaped LSPMVM and consequent-pole U-shaped LSPMVM have the highest torque density, while the consequent-pole SPM LSPMVM can be a better candidate where the low cost is desirable. Finally, the prototype of V-shaped LSPMVM has been manufactured, where experimental results match well with finite element analysis (FEA).

Performance Characteristics of a Dual-Stator, Spoke-Type Permanent Magnet Vernier Machine with Support Bar

Permanent magnet Vernier machine (PMVM) is a strong candidate for direct-drive applications in low-speed region because its power characteristic is higher than conventional permanent magnet machine (PMM). In this paper, the design of a dual-stator PMVM (DSPMVM) with spoke-type rotor is introduced. As a radial motor with dual-stator configuration, one on the outer and inner side, the rotor is equipped with support bars for practical and simple manufacturing, which is the aim of this study. The characteristics and performance of the proposed machine with and without the support bar are examined with finite element analysis (FEA). The DSPMVM and the support were manufactured and tested through experiments to verify proposed structure. Both simulation and experiment results show that there is little to no difference in performance when the support bar is equipped. Furthermore, the average deviation between simulation and experiment results is approximately 7% which is within the acceptable range.

Investigation of Permanent Magnet Vernier Machines From Armature Field Perspective

Permanent magnet Vernier machines (PMVMs) have drawn more and more attention due to their high torque density, whereas the power factor of PMVMs is lower than that of regular permanent magnet synchronous machines (PMSMs). At present, the analysis of PMVMs is mainly from the perspective of PM rotors, and the research results suggest that there seems a relationship between torque density and power factor. However, from the PM rotor perspective, the relationship cannot be explained in principle. In this article, the performance of PMVMs is investigated from the viewpoint of armature fields, where both the high torque density and the low power factor have been clarified. It is indicated that the high torque density of PMVMs is attributed to high amplitudes and large variation gradient of armature working harmonic, which has the same pole-pair of PMs, whereas the power factor suffers from the lower proportion of armature working harmonic to total harmonics. Meanwhile, the negative coupling between torque capability and power factor is first revealed from the armature field perspective. Finally, two prototypes of 18/14/4 and 15/14/1 with the same 14-pole-pair PM rotors and different armature fields are built and tested, and the analysis results match well with finite element analysis (FEA) and experimental results.

Evaluation of Linear Permanent Magnet Vernier Machine Topologies for Wave Energy Converters

Today, the importance of using vernier machines in wave energy converters has increased because of its simple structure and ability to generate a lot of thrust force at low speeds due to the magnetic gear effect. The linear vernier permanent magnet machine has been designed in various structures. Proper design and selection of the main parameters of the machine will improve performance and increase the efficiency of the linear vernier machine. One of these parameters is the shape of the permanent magnets and how they are magnetically oriented. The novelty of this paper is the reduction of leakage flux, achieved by changing the shape and orientation of the permanent magnet. Three types of linear permanent magnet vernier machines with different permanent magnet structures and orientation, including V-shape, Halbach array and consequent-pole are presented. The considered machines have been compared to each other and to the existing machine in terms of airgap flux density, back EMF, PM flux, Inductance, thrust force, detent force, loss, efficiency, power factor, flux density and flux line, using the finite element method in the same conditions and with the same volume of permanent magnets. The results show that the magnetic orientation and shape of the permanent magnet have a considerable effect on the leakage flux, and all the proposed models have a lower leakage flux and better performance compared to the existing model.

Design and Analysis of T-Shaped Consequent Pole Dual PM Vernier Machines With Differential Magnetic Network Method

This article has proposed a novel design of dual permanent magnet (PM) vernier machine (DPVM) with T-shaped consequent pole (TCP) rotor. The analytical model of T-shaped magnet rotor based on differential magnetic network method is first derived. Given the additional optimizing parameter, edge arc difference, TCP rotor has the potential to produce 6% higher fundamental airgap flux density or 30% higher PM utilization ratio than regular fan-shaped consequent pole (FCP) rotor. The influence of magnet size parameters including magnet thickness, pole pitch ratio, and arc difference angle on airgap flux density of TCP rotor is then analyzed. The torque performance of TCP in regular consequent pole and dual PM consequent pole vernier machines are also studied. The comparison shows that TCP can produce higher torque than fan-shaped magnet in vernier machines. At last, a prototype of DPVM with TCP rotor is built and tested, which has achieved 28-N·m/L measured torque density.

Conceptual Study of Vernier Generator and Rectifier Association for Low Power Wind Energy Systems

In this paper, we study a wind energy conversion system designed for domestic use in urban or agricultural areas. We first present the turbine, which was specifically designed to be installed on the buildings that it supplies. Based on turbine characteristics, we perform analytical sizing of a Permanent Magnet Vernier Machine (PMVM), which will be used as a generator in our energy conversion system. We show the influence of this generator on system operation by studying its association with a PWM rectifier and with a diode bridge rectifier. We then seek to improve generator design so that the turbine operates closely to maximum power points, while using a simple and robust energy conversion system. We use simulation to show the improvements achieved by taking into account the entire energy conversion system during machine design.