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Five‐phase permanent magnet synchronous machine (PMSM) can operate under open‐circuit faults with the appropriate current regulations. However, the traditional current regulations based on the five‐phase half‐bridge inverter have to satisfy the constraint of zero neutral point current, which limits the fault‐tolerant performance of the machine. Thus, this paper investigates the current regulation based on the five‐phase six‐leg (FPSL) inverter, which relieves the zero‐neutral point current limitation, and both current regulations considering the maximum torque (MT) and minimum copper loss (MC) are derived under different open‐circuit conditions. The cost of the system has increased, but with the new regulations, better fault‐tolerant operation capability of the machine can be obtained under all kinds of open‐circuit faults. Moreover, with the introduction of the neutral point current, the machine can work under triple‐phase open‐circuit faults. In conclusion, the proposed control scheme based on the FPSL inverter expands the fault‐tolerant operation capability of the five‐phase PMSM. The experiment results prove the effectiveness of the proposed current regulation on increasing average torque or reducing copper loss under fault‐tolerant operation. [ABSTRACT FROM AUTHOR]

The new topology of the dual-armature flux-switching permanent magnet machine (DA-FSPM) leads to new characteristics and issues in the control of the machine, of which the mutual inductance of the two sets of armature windings is the most important one. This paper proposes a novel position–sensorless control method based on high-frequency injection (HFI) for DA-FSPM. The high-frequency model of the machine is derived, and the theory of the position estimation method is proposed. Different from the conventional HFI-based position estimation method, the proposed method utilizes the mutual inductance of the DA-FSPM rather than the machine saliency. Meanwhile, because the extracted position information based on the mutual inductance is more obvious, the proposed method also has better steady and dynamic performance. Then, the position observer based on the phase lock loop and the initial position detection method for the DA-FSPM is proposed. The experiments are executed on a DA-FSPM prototype with three-phase stator windings and five-phase rotor windings to prove the effectiveness and superiority of the proposed method. [ABSTRACT FROM AUTHOR]

This article investigates the influences of end turn length on consequent-pole Vernier permanent-magnet (CPVPM) machines. Four structures are compared to discuss the tradeoff between the end turn length and the gear ratio, and nine structures are compared to discuss the tradeoff between the end turn length and the winding factor. It is found that, when the end turn length is taken into account, the CPVPM machines with concentrated winding have the potential to produce larger torque than those with the distributed winding. Motivated by the above observations, an integral slot concentrated winding CPVPM machine is proposed to be a promising candidate in VPM machine family, which has high torque capability, small end turn length, good fault tolerance, and desired power factor. The influences of key design parameters are investigated. The machine prototype is manufactured, and the electromagnetic performances are experimentally validated. [ABSTRACT FROM AUTHOR]

This article develops a nonlinear analytical model (NAM) for predicting the magnet loss of surface-mounted permanent-magnet (PM) motors considering nonlinearity effect and slotting effect. The analytical expression of vector magnetic potential in the PM region is derived from Hague’s equation for slotless air-gap, and then, it is extended for slotted air-gap based on the conformal mapping method. The PMs, iron nonlinearity, and winding current contributing to the eddy current are all represented by equivalent current in the analytical model. The key of the proposed model is to solve the equivalent current of iron nonlinearity from the improved magnetic circuit model (IMCM) of iron region, where the air flux source is proposed to replace the air reluctance. It is found that the iron saturation can decrease the amplitude of flux density and therefore reduce the magnet loss. Based on the NAM, the magnet loss can be obtained with high accuracy and high efficiency, which is a powerful tool for the optimization of magnet loss in the motor design. The effectiveness of the proposed model is verified by the finite-element method. [ABSTRACT FROM AUTHOR]

This article analyzed and compared the complex permeance model (CPM) and nonlinear analytical model (NAM) for surface-mounted permanent magnet (SPM) motor using a voltage source inverter (VSI). For linear CPM, the slotting effect is represented using the improved complex permeance function that describes the real slot shape rather than infinitely deep slot. NAM is extended from CPM and it replaces the magnetic potential drop of stator iron by the equivalent virtual current in the slot-opening and tooth-tip to account for the nonlinearity effect. The nonlinear inductance of SPM motor including the main phase inductance, slot leakage inductance, tooth-tip leakage inductance, and end winding leakage inductance is calculated using the frozen permeability method, which is the key to solve the electric circuit with VSI. The instantaneous back electromotive force (EMF) is calculated from the nonlinear back EMF coefficient and the back EMF neglecting iron nonlinearity. The electromagnetic torque obtained from motor model is used in the mechanical model and then the rotational speed and rotor position are obtained for the electric circuit model. Hence, the iterative solving process for the motor system is established to calculate the transient performance of SPM motor using VSI. Compared with CPM, NAM can greatly improve the calculation accuracy, which is also validated by both finite-element model and experiment. Besides, the proposed NAM is computationally efficient, which is useful for both motor design and motor control. [ABSTRACT FROM AUTHOR]

This paper proposed a hybrid subdomain model (HSM) for calculating the magnetic field distribution of interior permanent-magnet (IPM) machine accounting for slotting effect, rotor saliency, and iron nonlinearity. In the constant permeability region, i.e., slots, slot-opening, and air-gap, three subdomains are introduced to represent their magnetic field. By applying the subdomains interface conditions and nonlinear boundary conditions, the analytical air-gap field solution can be obtained based on the governing Laplace and Poisson equation. For the iron region, the magnetic reluctance network (MRN) is proposed to account for rotor saliency iron and nonlinearity. The magnetic voltage source is introduced to represent the permanent-magnet (PM) while the air-gap flux source is used to replace the air-gap reluctance network, which is the key to guarantee the computational efficiency and high accuracy. The electromagnetic performances of both flat-shaped and V-shaped IPM machines are investigated to show the advantages of different IPM machine topologies analytically. The HSM predictions for both IPM machines are validated by finite-element (FE) analysis and experimental results. [ABSTRACT FROM AUTHOR]

This article investigates the influence of start rotor position on three-phase short-circuit (3PSC) current in dual three-phase surface-mounted permanent magnet (DTPSPM) machines. For DTPSPM machines with symmetrical winding configurations, the 3PSC analytical model considering PM flux linkage harmonics is developed. It shows that the variations of 3PSC peak current with start rotor position mainly repeat every multiple of π/3 in an electrical period due to the fifth and seventh harmonics. The start rotor positions causing the largest 3PSC peak currents heavily depend on the harmonic magnitudes and phases. Then, the 3PSC analytical model for DTPSPM machines with asymmetric mutual inductances in one winding group is developed. It shows that the variations of 3PSC peak current with start rotor position mainly repeat every multiple of π. For winding configurations with smaller Mac, Mbc, and Mab, start rotor positions causing the largest d-axis peak current are about π/6+kπ, π/2+kπ, and 5π/6+kπ (k = 1, 2, 3…), respectively. To obtain the largest q-axis peak current, such start rotor positions are about 7π/24+kπ, 5π/8+kπ, and 23π/24+kπ (k = 1, 2, 3…). In addition, the influence of rotor speed and asymmetric level is discussed. Finally, finite-element simulation is performed and experiments are conducted to validate the theoretical analysis. [ABSTRACT FROM AUTHOR]

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

This article investigates the influence of design parameters on average torque and compares the electromagnetic performances of novel dual-armature flux-switching permanent magnet (DA-FSPM) machines with different stator core shapes. Firstly, the topology of novel E- and C-core DA-FSPM machines are proposed and their operating principles are introduced. Secondly, the influence of design parameters on average torque of U-, E- and C-core DA-FSPM machines are analyzed in detail, including the stator to rotor copper loss ratio, split ratio, magnet arc, stator tooth arc, stator yoke thickness, rotor tooth arc and rotor yoke thickness. Then, the key parameters of the machines are sequentially optimized to maximize the average torque. It shows that the optimal parameters of the DA-FSPM machines are no longer the same as their FSPM counterpart machines. Furthermore, the electromagnetic performances of the optimized DA-FSPM machines and their FSPM counterpart machines are compared, including the phase back-EMF, electromagnetic torque, overload capability, inductances, power factor, efficiency, and unbalanced magnetic force. Finally, the finite-element analyses are validated on two prototype machines. [ABSTRACT FROM AUTHOR]

It has been proved that dual-armature permanent magnet (PM) machines have higher power density than conventional PM machines under the same copper loss. However, the thermal conditions of these machines are different. This paper makes a fair comparison between a dual-armature linear switched flux PM machine (DALSFPMM) and a linear surface-mounted PM machine (LSPMM) by considering both electromagnetic performances and thermal conditions. First, the topologies of two machines and platform are introduced. Then, the 2D and 3D finite element (FE) models are employed for the electromagnetic and thermal analyses, respectively. During the machine optimization, the thermal analysis is used to determine the copper loss under the fixed machine dimensions, while the electromagnetic analysis is used to optimize the machine dimensions under the fixed copper loss. After iterations, two machines are optimized and their performances are compared. Under the limitations of 80 °C maximum PM temperature and 120 °C maximum winding temperature, the DALSFPMM can exhibit 38% higher thrust force density for the continuous duty and up to 43% higher thrust force density for the short-time duty. Finally, a prototype machine of DALSFPMM is tested to validate the analyses. [ABSTRACT FROM AUTHOR]

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

Doubly salient permanent magnet (DSPM) machines suffer from a large torque ripple due to unbalanced three phases, nonsinusoidal-phase back electromotive force, large cogging torque, etc. To suppress the torque ripple, this article proposes a new type of stator/rotor-pole number combinations. The number of stator poles is 18, while the number of rotor poles differs from the conventional counterpart (i.e., 12) by one. The DSPM machines with different stator/rotor-pole number combinations are globally optimized under the fixed copper loss and machine envelope. It shows that compared with the 18/12 stator/rotor-pole DSPM machine, the torque ripples of 18/11 and 18/13 stator/rotor-pole DSPM machines are reduced significantly, while their torque densities remain almost the same. An 18/13 stator/rotor-pole DSPM machine is built and tested so as to experimentally verify such improvement. [ABSTRACT FROM AUTHOR]

In this paper, the mathematical model of a novel 12-stator-pole/10-rotor-tooth doubly-fed flux-switching permanent magnet (DF-FSPM) machine employing 3-phase stator winding and 5-phase rotor winding is established and analyzed. Firstly, the stator and rotor winding inductance waveforms are analyzed in stator reference frame and modeled as the functions of rotor position considering major harmonic contents. Then, the inductances are transformed from the stator reference frame into the rotor reference frame using two Park transformation matrices, all of which become constants after the transformation. Thereafter, the voltage equation, power equation, torque equation are derived step by step. It shows that the magnetic coupling between stator and rotor windings causes the phase voltages to be affected by both stator and rotor currents. However, the reluctance torque and the torque produced by the magnetic coupling between stator and rotor windings are negligible. Further, the flux weakening capability of the machine is predicted from the voltage and torque equations. The power factors are analytically calculated and compared with the finite-element analysis, which indicates that both the stator and rotor of DF-FSPM machine exhibit high power factors. Finally, experimental validation is carried out on a prototype machine. [ABSTRACT FROM AUTHOR]

This article compares the electromagnetic performances of doubly salient permanent magnet (DSPM) machines with different stator iron core segments. Since the permanent magnets (PMs) of the DSPM machines studied in this article exist in pairs, the feasible numbers of PMs in the 12/8-pole DSPM machine are 12, 6, 4, and 2, and thus, the corresponding stator tooth number between two adjacent PMs is 1, 2, 3, and 6, respectively. Therefore, the stator iron core segments of the four DSPM machines have different shapes. Furthermore, to improve the average torque, PMs are inserted into the slots, and flux focusing teeth are adopted. All four machines are designed to achieve larger average torque under the fixed copper loss and envelope size. The comparison shows that the DSPM machine with two stator teeth between adjacent PMs exhibits the largest average torque and the smallest torque ripple. Moreover, the DSPM machine with six stator teeth between two adjacent PMs has the optimal PM utilization. To verify the predicted results, a 12/8-pole DSPM prototype with two stator teeth between adjacent PMs is manufactured and tested. [ABSTRACT FROM AUTHOR]

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

This article compares the doubly salient permanent magnet machine (DSPMM) having 18/13-pole number combination with 18/17-pole biased flux permanent magnet machine (BFPMM) to verify its improvement in torque characteristics. In such DSPMM, the stator/rotor-pole number combination is 18/13 rather than the conventional one (i.e., 18/12) to achieve balanced three phases, sinusoidal phase flux linkage and back electromotive force (back EMF), small cogging torque, and low torque ripple. On the other hand, an 18/17-pole BFPMM having the similar structure with the 18/13-pole DSPMM is analyzed, which has the best torque performance among such machines with the same stator pole number. To further improve average torque, the inner-type flux focusing (IFC) method is employed in both 18/13-pole DSPMM and 18/17-pole BFPMM. Then, both machines are optimized under the fixed copper loss and envelope size. The comparison shows that both machines have comparably small torque ripple while the 18/13-pole DSPMM with IFC (IFC-DSPMM) exhibits 35% higher torque density and 100% higher ratio of torque to PM volume. An 18/13-pole IFC-DSPMM is manufactured and tested to experimentally validate the predicted results. [ABSTRACT FROM AUTHOR]

In this article, two doubly fed (DF) flux-reversal permanent magnet (FRPM) machines with different PM arrangements are proposed, both of which have an additional set of armature winding in their rotor slots to further enhance the torque performance. Together with their one-set armature winding counterparts, comprehensive analyses and comparison among these four machines are conducted. The operation principles and winding configurations of these four machines are firstly introduced. Then, based on finite-element (FE) method, the electromagnetic performances of four machines after optimization with the purpose of maximum torque are compared in terms of no-load, on-load, and over-load capabilities. The results show that the DF-FRPM machine with consequent-pole structure offers the highest average torque and lowest torque ripple, which make it a promising candidate for low-speed and high-torque applications. A prototype machine has been manufactured and the FE results have been verified. [ABSTRACT FROM AUTHOR]

This article proposes a novel axially magnetized Vernier permanent-magnet (AMVPM) machine which has permanent magnets (PMs) clamped on both ends of the rotor with alternately magnetized directions. The topology improves the mechanical strength of the structure without weakening the electromagnetic performances. The detailed operating principles are described and the design parameters are optimized. The open-circuit back electromotive force (EMF) is calculated analytically by using the harmonic series expressions. Then, a comparison between the AMVPM machine and regular Vernier permanent-magnet (VPM) machine is analyzed by finite-element analysis (FEA) method. Finally, the machine prototype is manufactured and the electromagnetic performances are experimentally validated. [ABSTRACT FROM AUTHOR]

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

The clamping bolts and bolt-holes can be employed to stack the steel laminations in permanent magnet machines. Their influence on the electromagnetic performance is analyzed in this paper, including the electromagnetic torque, open-circuit torque, phase back-EMFs, and circulating current loss. A restraining method of dummy bolt-hole is proposed to achieve both balanced phase back-EMFs and zero circulating currents in bolts. The ratio of bolt-hole edge thickness to bolt-hole radius is optimized to compensate the reduction of stator yoke caused by bolt-holes. Besides, a method of open bolt-hole edge is proposed to restrain the circulating currents. Furthermore, structure analyses are conducted to prove the reliability of the electromagnetic design. The proposed method is verified by experiments on a prototype machine. [ABSTRACT FROM AUTHOR]

This paper proposes a subdomain model for open-circuit field prediction in dual-stator consequent-pole permanent magnet machines. The whole field domain is composed of four types of sub-domains, including magnets, air gaps, slot openings, and slots. The proposed model takes the effect of tooth-tips into account, which can accurately calculate the flux density in slots and cogging torque. The finite-element (FE) model is established, which validates that the proposed subdomain model can quickly and accurately predict the magnetic field distribution and cogging torque in dual-stator consequent-pole permanent magnet machines. [ABSTRACT FROM AUTHOR]

In this paper, a novel hybrid permanent magnet variable flux memory machine using two-part rotor is proposed whose rotor comprises an AlNiCo part and a NdFeB part adjacent to each other on the same shaft. With the proposed topology, flexible flux controllability can be achieved since the magnetization state of AlNiCo can be adjusted by a temporary current pulse. The detailed operating principles are described, and the split ratio and some key design parameters are optimized. Then, the electromagnetic performance of the proposed machine with emphases on back electromotive force, flux density, flux-weakening performance, and torque characteristics is investigated. Finally, 3-D finite-element validation is implemented and a machine prototype has been manufactured and tested to validate the analyses. [ABSTRACT FROM AUTHOR]

This paper focuses on the comparison of electromagnetic performance of the superconducting permanent magnet (SCPM) generators with two different topologies. The torque capabilities of the two generators are first investigated. The peak torque is largely restricted by the material characteristics of the superconducting (SC) and the permanent magnet. The SCPM generators with iron-cored rotor and iron-cored stator topology (IRIST) is superior to the one with iron-cored rotor and air-cored stator topology in terms of torque capability. Furthermore, the flux density, line electromotive force, torque and its torque ripple, and the efficiency of the designed generators are evaluated by using numerical model. The simulation results confirm that IRIST has higher output torque and efficiency with the penalty of higher harmonics and torque ripples. [ABSTRACT FROM AUTHOR]

This paper presents an electromagnetic design of a permanent magnet superconducting wind power generator with different stator teeth structures and armature winding arrangements. The main contribution of this paper is that a novel stator configuration is proposed, which is beneficial for superconducting machines. The topology of tapering poles makes it possible for the machine to carry larger current without severe magnetic saturation in the stator teeth. Meantime, the distributed arrangement of wires in the stator slot can reduce the ac loss in the same output power condition. Finite element analysis with commercial software is used to support these results. [ABSTRACT FROM AUTHOR]

A flux-weakening control algorithm with an improved stator flux linkage command's adjustment part of interior permanent magnet synchronous motors is proposed in this paper. The current commands are derived from lookup tables, which consider variation of motor parameters. The merits of this algorithm are the maximization of torque and high torque stability. Experimental results are demonstrated to verify the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

This paper develops an analytical model for predicting the magnetic field, back-electromotive force (EMF), and electromagnetic torque of surface-mounted permanent magnet machines accounting for magnet geometrical shaping and varied magnet property distribution. The magnets on the rotor are represented by the remanence, thickness, and magnetization direction functions. They are finitely segmented into magnet pieces of simple regular shape and uniform magnet property. The magnetic field of the machine is obtained by the superposition of the magnetic field due to each segment. The back-EMF and electromagnetic torque are also calculated. Using the developed model, the technique of mixed magnet material is investigated on a four-pole/six-slot machine. The analytical predictions are verified by both finite element and experimental results. [ABSTRACT FROM PUBLISHER]

This paper presents a novel outer rotor permanent-magnet vernier machine (PMVM) for in-wheel direct-drive application. The overhang structures of the rotor and flux modulation pole (FMP) are introduced. The soft magnetic composite (SMC) was adopted in the FMP overhang to allow more axial flux. The 3-D finite element analysis (FEA) was carried out to prove that the proposed machine can effectively utilize the end winding space to enhance the air-gap flux density. Hence the PMVM can offer 27.3% and 14.5% higher torque density than the conventional machine with no overhang structure and the machine with only rotor overhang structure, respectively. Nevertheless, the efficiency of the proposed machine is slightly lower than the conventional ones due to the extra losses from the overhang structures. [ABSTRACT FROM AUTHOR]