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In this article, slot-PM-assisted consequent-pole-PM machine (SPMA-CPMM) is proposed. The key is that the consequent-pole ferrite PMs are employed in the stator yoke to reduce the PM material cost largely, while a small amount of tangential magnetized rare-earth PMs is placed in the slot opening to improve the torque production. This proposed hybrid magnet design can greatly enhance the PM utilization ratio and reduce the PM cost while maintaining a relatively large torque density. In this article, the configurations of ferrite-PM machine (FPMM), consequent-pole ferrite-PM machine (CFPMM), and SPMA-CPMM are illustrated, while equivalent magnetic circuits (EMCs) of them are compared. Then, the electromagnetic performances of three machines are investigated and compared, which verifies the validity of the proposed machine. [ABSTRACT FROM AUTHOR]

This article presents a novel slot permanent-magnet-assisted hybrid-magnet memory machine (SPMA-HMMM) with hybrid permanent magnets (PMs) in both stator yoke and slot opening. The key is each pair of yoke PMs is composed of one pole of high coercive force (HCF) PM and one pole of low coercive force (LCF) PM with flexible flux regulation. LCF PMs can be freely magnetized and demagnetized through dc current pulses, which are supplied by dc excitation coils wound on LCF PMs. This design leads to high efficiency of machine due to negligible field excitation loss. In this article, the machine configuration and operation principle are illustrated in detail. An equivalent magnetic circuit is modeled to unveil flux regulation and parallel excitation effect. Then, the electromagnetic performances of SPMA-HMMM under different magnetization states (MSs) are investigated, which verify flux regulation ability of the proposed machine with changeable MSs of LCF yoke PMs. [ABSTRACT FROM AUTHOR]

The transverse flux tubular linear machine (TF-TLM) has merits of high power density and efficiency. However, excited by constant permanent magnet (PM), it is hard for TF-TLM to regulate its flux effectively, which restricts its further application in wave energy conversion (WEC). In contrast, the inherent higher order harmonics existing in the induced voltage may cause the additional loss and produce overvoltage, which should be eliminated to prompt power quality. Therefore, to strengthen the flux regulation capability of TF-TLM and improve the generated power quality, a novel hybrid-excited TF-TLM (HE-TFTLM) with complementary structure is proposed in this article. The key is that a parallel and complementary structure is constructed for hybrid excitations of both dc windings and PMs installed on the stator to enhance the flux regulation capability and eliminate the even-order harmonics in the induced voltage. In addition, the stator consequent-pole design boosts the output thrust density. According to the 3-D finite element analysis (FEA) results, output thrust force reaches 279.14 N, and the power density of the proposed machine can be effectively improved to 154 kW/m3 at rated excitation. [ABSTRACT FROM AUTHOR]

In this article, a novel winding switching control strategy is proposed to extend the speed range of a consequent-pole ferrite-permanent magnet hybrid-excited machine (CPFPM-HEM) for electric vehicle application. The key is that in low-speed range, the ac armature winding and dc field winding are connected in series to achieve large starting torque, while in high-speed range, dc field winding is injected with adjustable dc currents to realize variable speed constant voltage of ac armature winding. Furthermore, consequent-pole rotor is used to reduce the usage of the permanent magnet (PM). In the meantime, ferrite PMs are used to replace rare-earth PMs to reduce the cost with the shortage of rare-earth resources. In this article, the machine configuration, operation principle with dual excitation sources, flux modulation principle, and winding switching strategy are illustrated in detail. Then, the electromagnetic performance of the CPFPM-HEM in different speed ranges is investigated. Finally, the speed range extension with winding switching strategy is verified by the Maxwell/Simplorer co-simulation. [ABSTRACT FROM AUTHOR]

Reluctance machines with dc excitation coils have become a promising solution for electric vehicle propulsion system because of its robust rotor structure and good field-weakening ability. However, these machines usually suffer from relatively low torque density and efficiency. To solve this problem, this article proposes a novel hybrid reluctance machine with improved torque density and efficiency. The key novelty is to introduce skewed permanent magnets (PMs) in slot openings. The tangential component of skewed PMs can be used to relieve the dc saturation in the stator iron core, so that the $B-H$ working range can be extended and relatively high dc excitation can be applied in the proposed machine. Besides, the radial component of skewed PM provides extra torque component under flux modulation effect. Therefore, the proposed skewed PMs can achieve torque boost and core utilization improvement simultaneously. In this article, the dc-saturation-relieving effect of the proposed design is thoroughly investigated and verified by finite element analysis. [ABSTRACT FROM AUTHOR]

This article proposes a novel compact dual-permanent magnet (PM) dual-stator generator for hybrid ac/dc generation system. Two sets of windings are installed in the inner and outer stator separately. It has two electric ports, in which one is used to generate ac voltage and the other electric port that also generates ac voltage is rectified to obtain the dc voltage. The key of the generator is that two stators share one rotor with consequent PM structure, and the output power of the machine is much higher than that of the machine with only one stator. Besides, with two separated stator core and armature windings, the reliability of the proposed generator is improved. The advantage of the proposed dual-stator dual-PM generator is illustrated theoretically, and its slot/pole selection guideline is given. Comprehensive sensitivity analysis of the proposed generator is performed and multilevel design optimization method is adopted. The efficiency, torque ripple, and total harmonic distortion of the inner and outer armature windings of the generator after optimization are calculated to verify the effectiveness of the proposed machine design. [ABSTRACT FROM AUTHOR]

This paper proposes a novel direct-drive dual-PM motor for electric automatic guided vehicles (AGV). The proposed motor has split teeth on stator and dual PMs in stator and rotor sides, which contributes to reduced torque ripple, and enhanced torque. The airgap field of the proposed motor is analyzed theoretically, and the slot/pole selection guide line is concluded. The simulation results of the airgap flux density are shown and Fourier Transformation (FFT) analysis results agree well with the theoretically analyses results. Besides, the effects of design parameters of the proposed motor to the performances of the proposed motor are investigated. And it is found that reduced slot open could produce improved efficiency and decreased torque ripple. The efficiency of the proposed motor is relatively high within the operation range. A corresponding prototype is fabricated and the experiment validates the design. [ABSTRACT FROM AUTHOR]

This paper aims to propose a new Vernier reluctance machine (VRM), which integrates the advantages of a robust rotor structure, good torque density, and flexible flux control ability. The key is to establish the excitation field with both stator slot permanent magnets (PMs) and zero-sequence current. Two excitation sources have different pole pair numbers but share a parallel magnetic circuit and contribute to superimposed torque in this machine. Meanwhile, a flexible flux control can be achieved by regulating zero-sequence current, and little demagnetization risk exists for slot PMs during flux control. In this paper, the machine configuration and operation principle are introduced, along with its integrated ac and dc drive method. Electromagnetic performance of this new machine is evaluated by finite-element analysis. Leading design parameters are determined and optimized considering optimal injection ratio of zero-sequence current. A prototype is fabricated, and relevant experiment results demonstrate the feasibility of the proposed solution. [ABSTRACT FROM AUTHOR]

A novel parallel-hybrid dual permanent magnet (PM) machine topology with both enhanced torque density and improved flux weakening capability is proposed for electric vehicle propulsion in this paper. The key is to artificially construct the harmonics diversity with a single-layer concentrated armature winding in the stator and thus simultaneously couple the armature field with the excitation field produced by slot PM, rotor PM, and stator dc source, respectively. Enhanced torque density is obtained in this new topology due to the symmetrical flux-modulation effect between dual PM sources. Moreover, benefiting from a parallel excitation characteristic of hybrid magnetic circuit, the demagnetization risk is significantly mitigated for slot PM source and thus an extended flux weakening range is obtained. In this paper, the proposed new topology and its design mechanism are investigated, along with its electromagnetic performance evaluated based on finite-element analysis. Further, some leading design parameters are analyzed and determined to provide a design guideline for the proposed new topology. Finally, a prototype is built and fully tested. Relevant experimental results agree well with the finite-element predication. [ABSTRACT FROM AUTHOR]

This paper proposes a new Vernier reluctance machine (VRM) drive for electric vehicle. The key is to incorporate both stator-slot permanent magnets (PMs) and zero-sequence current as the excitation source to establish a parallel magnetic field and interact with armature winding. In this way, two different machines, namely, slot-PM-excited VRM and dc-excited doubly salient machine, are artificially integrated into a single structure, which contributes to enhance the torque density. Moreover, flexible flux control can be realized by regulating zero-sequence current. In this paper, the machine structure and operation principle are introduced, with its feasibility verified by both finite-element analysis and prototype experiments. [ABSTRACT FROM AUTHOR]

A novel bidirectional flux-modulation permanent magnet (BFMPM) machine for stand-alone dc wind power generation is proposed in this paper. The key is to control the inner rotor position with a small servo motor, and with the bidirectional flux-modulation effect, the resultant induced voltages in two sets of stator windings can be adjusted accordingly. Consequently, in a wide wind speed range, the various-speed constant-amplitude-voltage operation is realized. The novel structure has two major merits. First, it has high reliability without the maintenance problems caused by mechanical gearboxes, slip ring assembly, and brushes. Second, the proposed system requires a low-cost uncontrolled diode rectifier, which enhances the reliability and reduces the cost of the system. The analytical model and operation principle of the BFMPM machine are illustrated and the simulation results using a finite-element method is presented. A prototype is optimized and fabricated. The experimental results agree well with the simulation results and verify the correctness of the analytical model and the effectiveness of the proposed structure. Therefore, the novel structure offers a potential solution to provide a stable dc power for the standalone condition, such as remote area and offshore island. [ABSTRACT FROM AUTHOR]

This paper proposes a new slot-permanent-magnet (PM)-assisted variable flux reluctance generator (VFRG) for the hybrid electric vehicles. Compared with the existing dc-excited VFRG, auxiliary PMs are introduced into stator slots, which can fully utilize the redundant harmonics excited by single-layer concentrated armature winding and boost power density significantly. In this paper, the generator structure, operation principle as well as the winding restriction are discussed. Different slot pole combinations are fully compared in terms of both no-load and on-load characteristics. Some important design parameters are redefined for this slot-PM-assisted topology based on a sensitivity analysis. To release cost burden, both rare-earth-magnet and ferrite-magnet-assisted designs are considered into optimization. The feasibility of this new topology is verified by using finite element analysis and prototype testing. [ABSTRACT FROM AUTHOR]

Due to the unique flux distribution, biased flux machines (BFMs) could be driven by biased current to realize flexible flux weakening or strengthening control. In this paper, the electric machines with biased flux are investigated. The key techniques such as constructing biased flux in coils, exploring topologies, developing coil connection patterns, and designing drive circuits are presented. Based on that, the general design guideline for double stator BFMs is concluded. To verify this analysis, one 12/11 (stator teeth/rotor teeth) double stator BFM prototype is built and tested. The proposed double stator BFM has good torque and efficiency performance. Meanwhile, the biased current including dc zero sequence is used to adjust the exciting field. The simulation and experimental results verify the validity and effectiveness of this machine design method and control strategy. The flexible flux modulation characteristic makes this kind of machines suitable for applications with wide speed range. [ABSTRACT FROM AUTHOR]

This paper proposes a novel multi-phase double-winding vernier permanent magnet (DW-VPM) wind power generator applied for hybrid ac/dc microgrid. The key is to employ two sets of windings, namely, ac windings and dc windings in the machine, which serve to produce ac power and dc power for microgrid, respectively. The permanent magnets (PMs) are surface mounted on the rotor, and the stator is designed with open slots. The stator teeth can act as flux modulator for the permeance difference between the stator teeth and the air. Therefore, the field excited by PMs can be effectively modulated. Besides the original harmonic used to induce sinusoidal back electromotive force (EMF) in the ac windings and generate ac power, another low-order harmonic can be generated, which is used to induce square wave EMF in the dc windings and generate dc power through diode-bridge rectifier. Since multi-phase windings can get the square wave EMF more easier, the dc windings are designed with six phases. By using time-stepping finite-element method, the electromagnetic performances of the proposed DW-VPM wind generator are comprehensively investigated and verified. [ABSTRACT FROM AUTHOR]

In this paper, a novel modular linear double-stator biased flux (LDSBF) machine is proposed for wave power generation. The operation principle based on flux path analysis is presented. And stator/rotor pole number combinations are discussed by using coil flux analysis. The modular LDSBF machine has better flux path distribution than its counterpart, namely, linear biased flux permanent magnetic machine. More than that, the topology of the modular LDSBF machine makes it feasible to modular design and easy assembly. The electromagnetic characteristics of four types of linear machines are analyzed and compared by using time-stepping finite-element method. The comparative study shows that modular LDSBF machine with improved performance is a good potential design for wave power generation. [ABSTRACT FROM AUTHOR]

This paper proposes a novel hybrid excited generator, which is suitable for a variable-speed wind power generation system. Two sets of excitation sources are employed, which are permanent magnets (PMs) on the rotor and the field windings on the stator. The rotor is design with PM-iron structure, namely the PMs and iron poles are alternatively located in rotor, which can provide PM excitation and flux modulating simultaneously. Meanwhile, the adjacent stator teeth are designed with different height, which enables the stator with flux modulating effect, and, therefore, bidirectional flux modulating can be achieved. Some specific harmonics excited by the rotor PMs can be effectively adjusted by the field current, and the back electromotive force and electromagnetic torque can be regulated accordingly. Therefore, the proposed generator can achieve constant voltage control and maximum power point tracking control by controlling the field current. The design considerations and field regulating principle are analytically investigated. An improved Tabu search algorithm is used to optimize the proposed generator, and finite-element method is used to realize preliminary study of the electromagnetic performances. A prototype is manufactured and experimental tests are conducted to verify the theoretical analysis and control strategies. [ABSTRACT FROM PUBLISHER]

With the increasing popularity of hybrid electric vehicles (HEVs), the demands of improving the fuel economy and energy efficiency of HEVs are enlarged. The technology electrical continuously variable transmission (E-CVT) system provides the opportunity to fulfill this requirement. However, conventional E-CVT with planetary gears suffer from frictional loss, high maintenance, and audible noise. Therefore, a series of gearless E-CVT propulsion systems are developed. Thereinto, a double-rotor single-stator brushless E-CVT having high torque density, reduced stator end winding length, and reduced copper loss was recently proposed. However, only torque of the E-CVT system is optimized by the genetic algorithm in the previous study. This paper adopts a differential evolution algorithm coupled with finite element method to optimize torque, energy efficiency, torque ripples, and multiobjective of the E-CVT system by reconfiguring the height of rotors, the areas of slots, and the height of yoke. It is simulated that by only tuning the weighting factors, the permanent magnetic machine in the E-CVT system can operate in the highest torque mode, highest energy efficiency mode, lowest torque ripples mode, and multiobjective optimization mode. [ABSTRACT FROM PUBLISHER]

This paper presents an optimal design methodology of a dual-mechanical-port bidirectional flux-modulated machine for electric continuously variable transmission in hybrid electrical vehicles. The machine utilizes bidirectional flux modulation effect to combine two rotors and one stator together, aiming to realize electrical and mechanical power flexible split and combination. Due to the complexity of the machine structure, conventional optimization methods using analytical model are inapplicable. Therefore, an effective and practical method that combines the genetic algorithm and finite-element method (GA-FEM) is proposed to optimize the design of the machine in this paper. Since the computational cost increases exponentially with the increasing of number of design parameters, to reduce the computational cost in the optimization process, the design parameters are divided into two levels basing on a sensitivity analysis. And, then, the sensitive parameters are optimized using the GA-FEM coupled method. Finally, a prototype is fabricated to verify the effectiveness of the optimal design. [ABSTRACT FROM PUBLISHER]

This paper presents a new magnetic-gear pole-changing hybrid excitation machine (MG-PCHEM), which can provide high torque density and improved flux-weakening ability. The key is to flexibly change the pole-pair number of inner excitation sources by injecting variable dc field currents, and, hence, regulate the dominant pole-pair flux components to realize an effective magnetic field adjustment. In the following paper, the machine configuration and its operation principle of flux control are introduced first. Then, the influences of some leading design parameters are analyzed including the slot-pole combination and other dimension parameters, and after which a comparative study is carried out with traditional single-stator topology. Based on the optimal design, electromagnetic performance of the MG-PCHEM is further evaluated by using the finite-element method. Finally, a prototype is designed, manufactured, and fully tested. Relevant experimental results verify the feasibility of this new hybrid solution as well as the finite-element predictions. [ABSTRACT FROM AUTHOR]

From a new stator-flux perspective, a comparative study between the series and parallel hybrid excitation machine (PHEM) is conducted and it is revealed that in PHEMs there still exist distinct stator-flux harmonic components during high-speed flux weakening operation, which could be further utilized to improve the torque capability at high-speed range. Inspired by this idea, an auxiliary winding is creatively introduced into PHEMs to recycle and utilize the magnetic field energy generated during the field regulation. A new design case is presented in this paper, in which two sets of armature windings with different pole pair numbers are arranged to realize the function of flux weakening operation and energy recycling, respectively. The feasibility of this new hybrid solution is evaluated by using the finite-element analysis. Furthermore, a prototype is manufactured and relevant experiments are performed. The experimental results agree well with the theoretical analysis and simulation results, which verify that the recycled energy can be effectively used to boost the output torque and power of PHEMs in the high-speed region. [ABSTRACT FROM AUTHOR]

This paper proposes a novel hybrid-excited dual-PM machine for electric vehicle propulsion. The key is to use an integrated stator winding to replace the armature winding and the field winding in the conventional hybrid-excited machine. The stator winding is excited by ac current with dc bias, in which the ac component is used to produce the rotating armature field, while the dc bias current is used for the flux regulation. Therefore, the function of the ac and dc windings can be incorporated and realized by using just one set of winding. The torque density and flux regulating capability can be improved, and the winding configuration is also simplified. In addition, dual-PM excitation structure combines the advantage of stator-PM doubly salient machine and rotor-PM magnetic-geared machine, which can further enhance the torque capability. The operating principle and control strategy of the proposed machine are discussed. The electromagnetic performances are studied using the time-stepping finite-element method. A machine prototype is manufactured and experimental tests are conducted to verify the effectiveness of the machine design. [ABSTRACT FROM PUBLISHER]

This paper proposes a new brushless contra-rotating power split transmission (CR-PST) system for the direct-drive wind power generation. The core element of this system is a doubly fed dual-rotor flux-modulation permanent magnet machine, which has two contra-rotating rotors connected with two wind blades to absorb the wind energy, and two sets of stator windings to realize torque split between the two shafts. This proposed CR-PST system has compact structure and bidirectional flux-modulation design, as well as increased wind power conversion efficiency. Compared with the conventional wind turbine system, which can only work with single maximum power point tracking (MPPT) control strategy, the proposed CR-PST system can collect increased wind energy with dual MPPT method for the given wind speed. Time-stepping finite-element method is used to analyze the steady and dynamic performance of the proposed system and the control strategy is verified by experiments and simulation results. [ABSTRACT FROM PUBLISHER]

This paper presents a novel hybrid-excited dual permanent magnet (PM) brushless machine with bidirectional flux-modulating effect. Two sets of windings are housed in the stator slots, in which the armature windings are used to produce the rotating magnetic field, and dc field windings are used to generate the excitation field. The air-gap flux can be regulated effectively by controlling the direction and magnitude of the dc currents, and hence the constant power operating region can be expanded efficiently. Meanwhile, both the rotor and the stator have PM excitations, and dual field modulating effect is artfully incorporated into the machine design to ensure an effective magnetic coupling among the magnetic fields excited by the armature windings, dc field windings and the two sets of PMs. The torque capability of the proposed machine can be improved. Through analytically studying the air-gap field harmonics, the working principle of the proposed machine is discussed. The electromagnetic performances are investigated using finite element method and verified by experimental results. [ABSTRACT FROM PUBLISHER]

The electrical continuously variable transmission system is a very promising concept for variable-speed constant-frequency wind power generation due to its ability of seamless speed adjustment. In this paper, a novel wind energy conversion system based on electrical continuously variable transmission is proposed. This system combines the merits of two popular wind generation concepts: It enjoys high torque density like the permanent-magnet synchronous generator system and, also, it needs only a partial-scale converter like a doubly fed induction generator system. With a special doubly fed dual rotor structure, the system realizes both speed variation and power generation within one single machine, which makes it very compact. Besides introducing its structure and working principle, the design and performance analysis of the machine are presented in this paper. A prototype is made and tested for validation. [ABSTRACT FROM AUTHOR]

A novel brushless electric continuous variable transmission (E-CVT) system is presented and optimized. The proposed system offers an alternative solution for a variable-speed constant-frequency operation of the wind turbine application. The key is to eliminate the gearbox and brushes in the machine and this E-CVT system comprises of two rotors and two stators within one machine. This design inherits and integrates the merits of the direct-drive permanent magnet generator and the doubly fed induction generator with the additional benefit of the improved torque density and the need for a low-cost partial-scale converter. The structure, operation principle, and performance are analyzed. Genetic algorithm is employed to optimize the parameters for maximizing its power density. Time-stepping finite-element method is used to analyze the dynamic performance of the proposed system. [ABSTRACT FROM AUTHOR]

A novel gearless and brushless power-split transmission system is proposed for a variable speed constant frequency wind power generation application. The key is to design a special hybrid axial–radial flux focusing structure, which has an improved utilization of permanent magnet (PM) materials. This design integrates the merits of two popular concepts—the direct-drive PM generator and the doubly fed induction generator. It is direct driven, with high torque density and in the meanwhile, it needs only a partial-scale converter. To improve the stability of the system, five phase currents are used for the control winding. A time stepping finite-element method is used to analyze the dynamic performance of the proposed system. [ABSTRACT FROM AUTHOR]

This paper proposes and implements a new single-phase magnetless flux switching machine (FSM) for rooftop wind power generation. The key is to integrate an outer-rotor FSM and an inner-rotor FSM with shared stator yoke and stator drum windings. In such a way, this proposed machine can not only realize flux switching function to regulate magnetic flux effectively, but also incorporate the field and armature windings within one stator to reduce the copper losses and improve the overall machine efficiency. Meanwhile, the structure is compact and rotors can be directly driven by blades to capture the wind power. The machine design guidelines from both magnetic and electric aspects are illustrated, the machine characteristics are analyzed by using time-stepping finite-element method, and the system performances are evaluated based on mathematical modeling. Both simulation and prototyping test are conducted to verify the validity of the proposed machine and system. [ABSTRACT FROM AUTHOR]

Finite-element method (FEM) has been widely used to analyze the performance of electric devices. Due to the nonlinear permeability of iron materials, Newton–Raphson method is usually used in FEM for nonlinear iteration. To accelerate the nonlinear convergence, one effective technique is proposed. The method is to use different relaxation factors for materials in the electric device. The difference between this proposed method and conventional method is that in conventional method only one relaxation factor is used for all solutions. With the proposed method the total computing time of iteration process of FEM can be reduced effectively. The proposed algorithm is tested on a highly saturated transformer to showcase its effectiveness. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to quantitatively compare two types of dual-permanent-magnet-excited (DPME) machines, one is with fewer stator poles and the other is with fewer rotor poles. Four different magnetization patterns of permanent magnets (PMs) are considered. Calculation results obtained using finite-element analysis demonstrate that with exactly the same usage of magnets and copper windings, the DPME machine with fewer rotor poles can offer significantly higher electromagnetic torque than that with fewer stator poles, and the torque ripple of the DPME machine with fewer rotor poles is lower than that with fewer stator poles. Another finding is that DPME machines can offer satisfactorily high-torque capability only when the two sets of PMs are with the same magnetization directions. [ABSTRACT FROM PUBLISHER]

This paper presents a novel gearless and brushless power split transmission system for variable-speed constant-frequency wind power generation application. The core element of this system is a novel axial-flux doubly fed dual-rotor permanent magnet machine. The key of the design is to utilize the flux modulation principle to modulate the magnetic flux in an axial-flux machine and use doubly fed stator winding to control the rotor rotation. This design combines the merits of direct-drive machines and doubly fed generators. As the mechanical problems related to brushes, slip rings, and gear boxes are successfully overcome, the operational reliability of the system is improved. The stator winding of the proposed system can be directly connected to the power grid, and the power rating of its associated frequency converter is reduced. Time-stepping finite-element method is used to analyze the dynamic performance of the proposed system. [ABSTRACT FROM AUTHOR]

This paper presents a hybrid-excited electric continuous variable transmission system for hybrid electric vehicles. The key of this paper is to develop a machine with dual mechanical port and dual electrical port to allow the mechanical power from the internal combustion engine and the electrical power from the electricity storage system to be combined and split according to different driving conditions. The main merit is that the radial flux and axial flux hybrid PM machine windings can be independently designed and continuously controlled. The magnets are innovatively arranged in a flux-concentration configuration to provide radial and axial magnetic excitations that interact with both stator windings as well as improving the torque density. The magnetic field distribution and the static and dynamic performances of the proposed machine are analyzed using the time-stepping finite element method. [ABSTRACT FROM AUTHOR]

A novel double-stator, double-rotor brushless electrical continuously variable transmission (E-CVT) system is proposed. This machine incorporates an inner stator which can fully utilize the space inside the inner rotor so as to reduce the volume of the machine. This design is based on magnetic flux modulating and magnetic gear effect to make the E-CVT system work in different operating modes. Different control modes of this proposed machine are also discussed and analyzed, including pure electric mode, hybrid mode, and battery charging mode. Time-stepping finite element method (TS-FEM) is used to analyze the dynamic performance of the machine. TS-FEM simulation results are reported to verify the validity of the proposed design. [ABSTRACT FROM AUTHOR]

Multiphase dc-excited Vernier reluctance machine (DC-VRM) exhibits the merits of robust structure, small torque ripple, and good fault-tolerant ability. Developing advanced sensorless drive methods can further promote its application in the safety-critical system. In this article, pulse injection sensorless drive methods are optimized in a six-phase DC-VRM parallel H-bridge drive system to strengthen their acceleration performance and fault-tolerant ability. The acceleration performance studied in this article corresponds to the acceleration speed during the startup stage. By the full-phase alternative pulse injection method (APIM), each phase can be excited independently to avoid mutual-inductance influence on position estimation, but this method suffers from a long communication delay and relatively poor acceleration performance. A reduced-phase APIM can reduce detection time, but the lack of detected phase may influence position estimation accuracy and fault-tolerant ability. To solve these problems, a novel vertical-axis synchronous pulse injection method is proposed and compared with previous methods in this article. The key is to inject detection pulses into vertical-axis phases simultaneously, thus reducing the detection time and improving the torque generation. It is proved that the influence of mutual inductance on position estimation can be ignored, and the detection accuracy and acceleration performance can be improved without deterioration of fault-tolerant ability. [ABSTRACT FROM AUTHOR]

A method to extract the equivalent parameters of transient electric circuit and magnetic field coupled problem based on sensitivity computation on the system equations is presented. The field equations are derived by using the finite element method. In contrast to traditionally used methods which are based on the physical meanings and physical relationships of the parameters, in this method, the parameters are extracted from the mathematical system equations which include the eddy-current magnetic field equations and internal circuit equations. Its advantage is that it is applicable to complex problems, inside which the reactive energy, iron losses, and copper losses are difficult to be isolated and expressed. The extracted parameters can include the effects of eddy currents, internal circuits, and mechanical motion. It has been applied to indirect coupling between external circuits and transient magnetic field with internally connected circuits. [ABSTRACT FROM PUBLISHER]

DC-Excited vernier reluctance machine (DC-VRM) using a 12-slot/10-pole-pair design, exhibits the advantages of small torque ripple and low cogging torque due to the inherent commentary characteristic. However, the inherent saliency is canceled out by a 12/10 pole combination of machine design driven by a traditional three-phase inverter. As a result, the sensorless operation in zero/low-speed regions becomes difficult because the position estimation methods using self-inductance detection cannot be applied. To tackle this problem, we first analyzed the saliency annihilation phenomenon through Fourier analysis that the odd-order harmonics in self-inductance are canceled. Moreover, reconstructing saliency method is proposed by splitting a phase winding into two sub-phase coils and using parallel H-bridge converters to supply sub-phase coils and achieve sensorless drive. Through this method, the saliency effect is recovered in self-inductance, thereby pulse injection sensorless drive can be applied. The constructed 12/10 DC-VRM sensorless drive shows good fault-tolerant ability and can be applied in safety-critical industry applications such as aerospace propulsion. Analysis and experiments are performed in the initial position detection, start-up and free-running stages to verify the feasibility of the proposed solution. A sector estimation accurate to 6° can be achieved. [ABSTRACT FROM AUTHOR]

Vernier reluctance machine (VRM) with dc field coils in stator is a competitive rare-earth-free design for variable-speed industrial applications due to its robust structure and controllable excitation, while its torque density is relatively disadvantageous. To address this issue, this article proposes a new armature winding design method for VRM with dc field coils across two stator teeth. The key is to break the traditional winding design principle based on the flux modulation effect of fundamental dc field harmonic, and instead, reconstruct a novel harmonic winding to enhance the utilization factor of the modulated high-order dc field harmonics arising from the unique magnetomotive force distribution of dc field coils across two stator teeth. By this means, the torque density can be improved by 75.6% against the existing poor counterpart. In this article, the machine structure and operation principle are introduced, with emphasis on the high-order dc field harmonics distribution rule and its influence on the armature winding design. By finite element design and optimization, a comparative study is performed to evaluate the electromagnetic performance of VRMs using two different winding configurations with variable slot pole combinations. A prototype is fabricated and tested, and the results agree well with finite element analysis, which verifies the feasibility and advantages of the proposed winding design method. [ABSTRACT FROM AUTHOR]

A line-start permanent magnet (LSPM) machine can be regarded as the integration of an induction motor and a permanent magnet synchronous motor (PMSM), so it has both self-starting capability as the induction motor and high efficiency as PMSM. As the cage winding on the rotor of LSPM only works at the starting process, it competes with permanent magnets for the space of a rotor. To solve this paradox, a steel-bar starting cage-based LSPM machine is proposed and analyzed in this article. Steel has larger resistivity than aluminum and copper, which can increase the starting torque and reduce the impact current of cage winding at the starting stage. Due to high permeability of steel, magnetic flux can also flow through steel-bar cage winding at synchronous speed. A steel-bar starting cage and a traditional aluminum starting cage winding are compared based on a four-pole LSPM machine using finite-element analysis (FEA) in this article. It is verified that although the self-starting capability of steel-bar cage winding is reduced due to the leakage flux, the performance at synchronous speed such as torque density and torque ripple is improved. [ABSTRACT FROM AUTHOR]

This article proposed a new slot-permanent-magnet (PM)-assisted hybrid reluctance generator (SPMa-HRG) with self-excited dc source for stand-alone wind power generation system. By introducing PM excitation in stator slot openings, enhanced torque density due to flux modulation effect can be achieved compared with the original reluctance topology. Moreover, the introduced PMs make it feasible to build a self-excited dc source to fed dc field winding without using extra power supply. In particular, a simple design of ac supply winding is proposed, by splitting a small portion of ac armature winding to provide electrical power to dc field winding through a diode rectifier and small-capacity H-bridge converter. Compared with using separate dc source, the device cost is reduced, and the system reliability is improved. In this article, the generator structure and operation principle are introduced. PM usage is optimized to obtain the optimal torque. The feasibility of the optimal design with self-excited dc source is verified by field-circuit coupled finite element analysis. [ABSTRACT FROM AUTHOR]

Due to the flux leakage and large detent force, the thrust force ripple of transverse-flux linear motor is relatively large, which restricts its further application. Also, the field of most existing transverse-flux machines is hard to be altered and regulated considering the permanent magnet (PM) excitation. Therefore, to suppress the force ripple and strengthen the flux regulation capability of transverse-flux machines, a novel hybrid excitation transverse-flux tubular motor with complementary structure is proposed in this article. The key is that a complementary and parallel structure is constructed in this motor, and hybrid excitation of both dc windings and small auxiliary PMs installed at opening of the slot is adopted in this motor as well. In addition, unequal teeth design of dc winding and ac winding is also employed to increase the thrust force density. Finite element calculation results verify the effectiveness of the proposed machine. [ABSTRACT FROM AUTHOR]

This paper incorporates the idea of integrated field and armature windings into the design of novel hybrid excited machines with bi-directional flux modulating effect, which results in a new hybrid-excited machine concept that is referred as dual-electrical-port dc-coil-free hybrid-excited machine (DEP-DCF-HEM). In the proposed design, dc field windings are eliminated and dc bias currents are injected into the windings to generate dc excitation field. In addition, the armature windings are divided into dual electrical ports, and zero-sequence current flows between these two ports can adjust the air-gap field effectively. Compared with existing HEMs with additional dc coils, the proposed machines can achieve both higher torque density and wider flux weakening range. The presented design principle can be utilized in a variety of configurations of DEP-DCF-HEMs. Topologies with stator permanent magnet (PM), rotor PM, and dual PM are possible designs, which are all investigated in this paper. A dual PM DEP-DCF-HEM prototype is manufactured, and experimental measurements are conducted to verify its performances. [ABSTRACT FROM AUTHOR]

In this paper, a new permanent magnet (PM) linear motor is proposed. This motor has a special structure with complementary stator flux, which helps to reduce the flux leakage and improve the utilization of the PM. The PMs are installed in a leaning manner, which increases the effective area of the PMs and enhances the field excitation. Hence, the force density of the motor can be improved and it will be, especially suitable for applications within a limited space. The motor structure and working principle are first explained. The design of the motor is then comprehensively investigated. An electromagnetic optimization method based on tabu search algorithm and finite-element method is proposed for the motor to improve its force density. [ABSTRACT FROM AUTHOR]

This article presents a novel doubly salient permanent magnet (DSPM) machine with enhanced torque performance. The key is that an assistive magnetic flux is produced by using two sets of slot PMs inserted into the slot openings, which can effectively improve the torque production. Besides, a complementary magnetic path is built by dual rotors with 180° angle shift to reduce leakage flux, which can effectively suppress the torque ripple. In this article, the proposed machine design is presented, including working principle, winding configuration, magnetic path analysis. Then, the Genetic Algorithm is used to find the optimal designs for the proposed machine. Further, to verify the effectiveness of the proposed machine, three doubly salient machines are compared, including the proposed machine, a DSPM machine without assistive slot PM design, and a dual-rotor DSPM machine without complementary rotor structure. Finally, a prototype of the proposed machine is built and tested to verify the validity of the proposed machine design. [ABSTRACT FROM AUTHOR]

Numerous research efforts are devoted to attain high performance and strong fault tolerance for the machine drives in safety critical applications, though the two aspects are conflicted in most cases. In this paper, a novel triple 3-phase PMA-SynRM with star-delta connected windings is proposed. The star-delta winding could produce a higher fundamental magneto-motive force and lower spatial harmonics than the conventional star winding. Therefore, it exhibits higher torque, lower torque ripple and lower iron loss, enhancing the healthy performance. In addition, the coils whose turn fault current is the highest are arranged in the inner delta part which provides circulating current path. It is demonstrated that the proposed winding solution reduces the fault current by 55% and the fault turn copper loss by 65%. Hence, the machine's fault tolerance is significantly improved. The machines with the star winding and star-delta winding are studied by detailed finite element calculation and experimental tests under various operation modes. Both the simulation and test results confirm that the proposed star-delta winding machine owns higher performance and stronger fault tolerance than the conventional star winding machine. Thus, it becomes a more competitive candidate for the high reliability drives. [ABSTRACT FROM AUTHOR]

This paper proposes a novel magnetic-geared tubular linear machine for tidal and wave energy conversion. The key of the proposed machine is to embed the armature windings into slots adjacent to the modulating segments of a linear magnetic gear (LMG). The compact component designed can serve simultaneously as the modulating poles in the LMG and the armature stator in the generator. When compared with its existing counterparts, the proposed machine has an improved force density and a simpler mechanical structure by virtue of its gearing effect. Moreover, Halbach permanent-magnet (PM) array is used to build up the PM arrays in both the inner mover and outer mover of the LMG, resulting in increase in thrust force density, reduction in cogging force, and high machine efficiency. The working principle of the proposed machine is introduced, and the electromagnetic performance is investigated quantitatively using the time-stepping finite-element method. [ABSTRACT FROM AUTHOR]

This article investigates rotor losses in permanent magnet Vernier machines. By analyzing air-gap field, the harmonic distribution and frequency of modulated open-circuit flux density and armature reaction flux density are obtained. Then, rotor losses production principle is revealed and the influence of each harmonic on the loss is analyzed. Meanwhile, the influence of each harmonic on torque is also studied. It is found that some harmonics have no contribution to torque but produce additional losses. On this basis, a new rotor structure is proposed to suppress the rotor losses. Comparison results indicate that by suppressing nonworking harmonics, the rotor losses can be reduced effectively without affecting the effective torque. Finally, the theoretical and finite-element analysis results are verified by prototype tests. [ABSTRACT FROM AUTHOR]

In this article, a novel winding switching strategy is proposed to improve the flux-weakening capability of a hybrid-excited reluctance machine (HERM). The key is that in low-speed operation, the primary and the secondary windings are connected in series and serve as armature winding to maximize output voltage while in high-speed operation, the secondary winding is switched to dc excitation winding to realize variable speed constant voltage output. The machine configuration, operation principle with dual excitation sources, winding switching concept, and manipulation circuit are illustrated in detail. Then the electromagnetic characteristics of HERM in different operation status are investigated. Finally, the variable speed constant voltage output of wind power generation system resorting to winding switching as well as dc excitation regulation is verified with Maxwell/Simplorer cosimulation. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to optimize the design of a dual-structure permanent magnet (PM) machine for the low-speed application. Multi-objective optimization using nondominated sorting genetic algorithm II (NSGA-II) is used to maximize the torque and efficiency while reducing the torque ripple of the machine. The torque, torque ripple, and efficiency of the optimized machine have significant improvement by optimizing the machine parameters within a fixed outer axial and radial length. This optimization process can be used to select the best machine design in different aspects’ requirement. [ABSTRACT FROM AUTHOR]

Low-speed flux-modulated permanent-magnet (PM) machines do not need to conform to the conventional design rule which requires identical number of pole-pairs in both stator and rotor. In flux-modulated machines, special ferromagnetic segments in the airgap are used to modulate the magnetic field. In this paper, a general rule to compare different types of electric machines as well as measures to improve the torque density in these machines are presented. In this paper, the energy conversion capacity of different machines with the same physical size and the same operating temperature-rise are compared. An adaptive-order method for modeling the load—temperature-rise relationship is presented to reduce the computing time for this inverse problem. Three power-electronic-driven PM electric machines, which are, namely, a traditional PM machine, a radial-flux-modulated machine (RFMM), and an axial-flux-modulated machine (AFMM), are analyzed and compared based on their temperature distribution and electromagnetic torque density using magnetic field and thermal field computation. Experimental results of an AFMM prototype are used to validate the temperature-rise which is computed using 3-D finite-element method (3-D FEM). [ABSTRACT FROM PUBLISHER]