Field Flux-switching Permanent Magnet Machine Research Articles

Investigation on the field regulation capacity in a hybrid excited axial field flux-switching permanent magnet machine for EV application

In this paper, a novel hybrid excited axial field flux-switching permanent magnet (HEAFFSPM) machine is presented, of which the high torque capability and flexible flux regulation make it suitable for EV application. The field regulation principle of the machine is investigated, and the analogical saturation effect at pro-magnetized condition is revealed. Then the influence of the machine design parameters on the field regulation capacity and output torque of a 3-phase 6/10 stator/rotor-pole HEAFFSPM machine are analyzed by 3-D finite element analysis (FEA) method under univariate optimization condition. With the slight decrease of the electromagnetic torque, both the analogical saturation effect under pro-magnetized condition and the high flux regulation capacity are effectively improved with multivariable optimization via design of experiments (DOE) method. Finally, a prototype has been manufactured and the analysis result is validated with the experiment result.

Investigation of cogging torque reduction for a 6/10 hybrid axial field flux‐switching permanent magnet machine by harmonic field current injection

Hybrid axial field flux-switching permanent magnet (HAFFSPM) machine exhibits a high-cogging torque due to its doubly salient structure and flux focusing effect. In consideration of the armature and field windings are both equipped in the HAFFSPM machine, a cogging torque reduction method by the harmonic field current injection is proposed in this study. Initially, the mathematical model of the HAFFSPM machine is analysed. Moreover, the theoretical principle of the proposed method is investigated based on the analytical model of the machine. The amplitude and phase angle of the injected current are calculated according to the harmonic component of the cogging torque. The feasibility of the proposed method is analysed and validated by both the finite-element analysis method and experiments on the prototype. Finally, the comparison between the proposed method and several topology optimisation methods of the HAFFSPM machine is given to indicate the priority of the harmonic field current injection method on cogging torque reduction.

Performance analysis and comparison for two topologies of flux-switching permanent magnet machine

Flux-switching permanent magnet (FSPM) machine is a kind of stator-typed permanent magnet machine, which is suitable for driving electric vehicles and hybrid electric vehicles because of their large power/torque density and high efficiency. The axial field flux-switching permanent magnet machine (AFFSPMM) and radial field flux-switching permanent magnet machine (RFFSPMM) with H-typed iron cores are reached and compared in this paper. On the condition of the same outer diameters and total volumes, the electromagnetic performances of the two machines are analyzed and compared by the three-dimensional finite element method, including the air gap flux density, inductance, back electromotive force (EMF), electromagnetic torque and loss. The finite element results show that the copper loss of AFFSPMM is higher than that of RFFSPMM at the rated load, however, the total loss of AFFSPMM is lower than that of the RFFSPMM. Meanwhile, AFFSPMM has greater torque than RFFSPMM in the constant power range. The related experiments are done to validate the finite element results, which are basically consistent with experiment results.

Model Predictive Torque Control of a Hybrid Excited Axial Field Flux-Switching Permanent Magnet Machine

Hybrid excited axial field flux-switching permanent magnet (HEAFFSPM) machine is a novel stator excitation hybrid excited synchronous machine, which combines the advantages of the axial field flux-switching permanent magnet machine and wound field machine. In this paper, two model predictive torque control (MPTC) methods with flux-adjusting strategy implementation for the HEAFFSPM machine, including the MPTC and MPTC with duty cycle control (MPTC-DCC) by optimizing the active voltage vector duration to reduce the torque and flux ripples, are proposed and comparatively investigated. Based on the theoretical analysis, a discrete-time model of the HEAFFSPM machine is established. Considering the flux-enhancing/-weakening strategies, the different multi-objective cost functions are designed. The multiple right weight coefficients are analyzed and chosen to optimize the operating performance of the drive system. The results indicate that the proposed MPTC-DCC method reduces the torque and flux ripples significantly compared with MPTC method, and the drive system has better steady performance. Meanwhile, the load capability in the whole speed region is improved and the constant power operating range is broadened by using the proposed flux-adjusting strategy.

Speed Sensorless Control of Hybrid Excitation Axial Field Flux-Switching Permanent-Magnet Machine Based on Model Reference Adaptive System

A novel 6/13-pole hybrid excitation axial field flux-switching permanent magnet machine (HEAFFSPMM) exhibits strong fault tolerance capability, high efficiency, and large torque density. However, merely few research on speed sensorless control in HEAFFSPMM exists. The speed sensorless control methods based on model reference adaptive system (MRAS) are studied and compared for the machine to improve the stability and reliability of the system and consequently improve the application of machine in control system. Based on the field-oriented control strategy, the MRAS observer of speed is designed and built by applying stator currents, stator flux linkages, and simplified stator currents. The three speed sensorless control algorithms of MRAS are compared and analyzed by using MATLAB/Simulink simulation and dSPACE1104 experimental platform. Results show that the speed sensorless control algorithm based on simplified stator currents has good control performance and high control accuracy.

Fault-Tolerant Control of Hybrid Excitation Axial Field Flux-Switching Permanent Magnet Machines

With the development of electric vehicles (EVs), the reliability and security of the motor drive system have been in high demand in recent years. EVs can still work reliably even when the motor drive system encounters some failures. Therefore, fault-tolerant motors have become the focus of research all over the world. The hybrid excitation axial field flux-switching permanent magnet machine (HEAFFSPMM) is a novel stator excitation brushless PM machine. It combines the advantages of AFFSPMM and hybrid excitation PM machine. Based on a 600 W prototype of three-phase 12/10 stator/rotor pole AFFSPMM, these parameters of HEAFFSPMM are optimized by 3-D finite element method in order to obtain the high self-inductance and low ratio of mutual and self-inductances, including the number of rotor poles, the split ratio, the width of permanent magnet, and the width of stator middle teeth. Then, the fault-tolerant control method of the space vector pulse width modulation based on minimum copper loss is proposed in this paper with the combination of adjusting the field current. The control methods of the HEAFFSPMM are simulated and investigated at healthy and one-phase open-circuit operation. Finally, the experiments are done to validate the proposed fault-tolerant control method. The results indicate that the HEAFFSPMM has good fault tolerance under the proposed control method.

Optimal Design and Analysis of the Novel Low Cogging Torque Axial Flux-Switching Permanent-Magnet Motor

The axial field flux-switching permanent-magnet machine (AFFSPM) is one of the most efficient machines which is appropriate for high torque and low-speed direct-drive applications. In this paper, the novel axial field flux switching machine with sandwiched permanent magnet (AFFSSPM) is proposed in order to increase torque density and decrease cogging torque. The proposed model equipped with an advanced phase-group concentrated-coil winding to obtain a unity displacement winding factor. Two three-phase 6-stator-slot (S)/10-rotor-pole (P) and 12(S)/19(P) configurations of the proposed model are investigated. Some specific design issues, including the sandwiching pole angle, the stator tooth angle, and the rotor pole angle have been optimized to obtain the maximum torque density and minimum cogging torque by artificial neural network and non-sorting genetic algorithm II. Moreover, the static electromagnetic characteristics are investigated. Compared with the conventional AFFSPM and 6(S)/10(P) AFFSSPM, the 12(S)/19(P) proposed machine shows higher torque density, lower cogging torque, and higher level of fault-tolerant capability. In order to improve the dynamic performance of the AFFSSPM motor, a space vector modulation-direct torque and flux control (SVM-DTFC) scheme is proposed. The AFFSSPM motor exhibits excellent dynamic performance with proposed scheme.

Dual rotor flux switching permanent magnet machines with phase-group concentrated-coil windings for high performance

This paper proposes a novel dual rotor radial field flux switching permanent magnet machine (FSPMM) with phase- group concentrated-coil (PGCC) windings and two misaligned rotors to obtain high performance, including high torque density and low cogging torque, as well as low torque ripple. The proposed FSPMM features a new combination of stator slots and rotor poles, which is determined by the winding configurations. The PGCC windings are adopted to obtain a unity displacement winding factor, and enhance the flux focusing effects together with the use of spoke-type PM constructions. The unaligned arrangement of two rotors will help to not only achieve further flux magnification by an alternate operating principle for PM flux concentration, but also suppress the cogging torque. To highlight the advantages of the proposed FSPMM, two conventional FSPMMs with typical machine configurations having concentrated windings are adopted for performance comparison based on a finite element method (FEM) using JMAG-Designer.

Analysis and Comparison of Axial Field Flux-Switching Permanent Magnet Machines With Three Different Stator Cores

Axial field flux-switching permanent magnet machine (AFFSPMM) is a novel brushless AC machine, which incorporates the advantages of flux-switching permanent magnet machine and axial field permanent magnet machine. It is suitable to be applied in the field of direct drive electric vehicles due to short axial size and large torque density. In the paper, the different stator core structures such as U-, C-, and E-shape are researched on basis of a three-phase 600 W conventional AFFSPMM. These parameters including rotor pole numbers, stator tooth shape, and the deflection angle of rotor pole are optimized for obtaining sinusoidal back electromotive force and small cogging torque. The electromagnetic performances are analyzed and compared by 3-D finite element method. It is found that C-core AFFSPMM can get higher output torque in comparison with U-core machine, and E-core machine can improve fault-tolerant capability and reduce the torque ripple.

Influence of design parameters on inductances of e-core axial field flux-switching permanent magnet machines

Purpose – Axial field flux-switching permanent magnet machine (AFFSPMM) can be applied in the field of electric and hybrid electric vehicles because of short axial size, large torque density, and high-power density. The purpose of this paper is to improve the reliability of AFFSPMM itself, the design parameters have to be considered for attaining high self-inductances and reduced mutual-inductances. Design/methodology/approach – The original parameters of E-core AFFSPMM are designed with reference to a 600 W prototype, on the basis of which the 3-D model of the original AFFSPMM is established, and the inductances are calculated by finite element method. The influence of these parameters on the inductances, including combinations of stator and rotor pole numbers, spilt ratio, stator side tooth width, magnet thickness, and rotor pole width etc., are respectively investigated and analyzed under the constant copper loss. Findings – The relationships of rotor pole numbers and inductances are deduced on the condition of the fixed stator poles. It is found that the rotor pole numbers has significant effects on the ratio of mutual-inductance to self-inductance, and the self-inductance is mainly affected by the rotor pole numbers, the split ratio, the stator tooth width, and the rotor pole width. The asymmetry of back-EMF can be largely reduced by optimizing the rotor tooth width. In this paper, the static characteristics are compared and analyzed for the original and optimal 6/14-pole AFFSPMM. Meanwhile, the open-circuit and short-circuit fault are investigated by transient analysis. The results show that the optimized E-core AFFSPMM has good fault tolerance. Originality/value – The research of inductance characteristics for E-core AFFSPMM is valuable to design the fault-tolerant machine, by which the cost of control and manufacture can be largely saved.

Design and Analysis of Novel Hybrid-Excited Axial Field Flux-Switching Permanent Magnet Machines

The axial field flux-switching permanent magnet machine (AFFSPMM) is a novel brushless AC machine. The magnets and concentrated windings are both in the stator instead of the rotor. The short axial length is beneficial to save the place of electric vehicles (EVs). Furthermore, the AFFSPMM exhibits the advantages of high power density and torque density. However, it is difficult to regulate the air-gap field since the field is produced by magnets alone. The fault-tolerant capability needs to be enhanced in the application of a direct-drive EV. Hence, a novel hybrid-excited AFFSPMM is proposed, in which the air-gap field can be easily regulated and the mutual inductance is largely reduced. In this paper, the design parameters of the novel machine, such as the split ratio, the rotor pole numbers, the rotor pole width, etc., are optimized in order to attain a sinusoidal back-EMF waveform and low cogging torque. Moreover, the static performance including each phase flux-linkage, inductance, and torque is analyzed on the basis of the 3-D finite-element method (FEM).

Cogging Torque Reduction of Axial Field Flux-Switching Permanent Magnet Machine by Adding Magnetic Bridge in Stator Tooth

Axial field flux-switching permanent magnet machine (AFFSPMM) is a novel stator PM machine with high torque density and efficiency. The cogging torque in AFFSPMM is larger than that in the traditional PM machine because of the double salient structure. In order to decrease the cogging torque, the analytical expression of the cogging torque is deduced and a cogging torque reduction method by adding magnetic bridge in adjacent stator tooth is proposed. Based on the 3-D finite-element (FE) method, the influence of the magnetic bridge thickness on the cogging torque and the output torque is analyzed and compared with the rotor skewing and notching methods. The influence of the stator tooth and rotor pole width on the output torque is studied. The 3-D FE analysis is compared with the experimental results. The research results show that the proposed method is effective in the reduction of cogging torque for all kinds of stator structures. Moreover, the cogging torque can decrease greatly and the average output torque decreases slightly when combined with the optimization of the stator tooth width and rotor pole width.

Novel Fault-Tolerant Design of Axial Field Flux-Switching Permanent Magnet Machine

Axial field flux-switching permanent magnet machine (AFFSPMM) has significant advantages, such as the short axial size and high torque density. It is suitable for the direct drive in-wheel applications for the electric and hybrid electric vehicles. For improving the reliability, a novel fault-tolerant structure is applied in the AFFSPMM. The stator is composed of E-shaped laminated segments. The phase windings are physically isolated to each other by the middle teeth of E-shaped cores. The field windings wounded around the middle teeth are used to regulate air-gap flux in the proposed machine. The electromagnetic performances are investigated and analyzed by three-dimensional finite element method (FEM), including the inductance, the back-EMF, and the torque capability, etc. It is shown that the fault tolerance is improved in the novel AFFSPMM, and a wide speed range of operation can be attained by a small DC field current.

Static Characteristics of a Novel Axial Field Flux-Switching Permanent Magnet Motor with Three Stator Structures

A three-phase 12/10-pole axial field flux-switching permanent magnet machine (AFFSPMM) with three different stator structures, including parallel permanent magnet and parallel slot (PPPS), parallel tooth and parallel slot (PTPS), and parallel permanent magnet and parallel tooth (PPPT), is analyzed. Based on a 3-D finite element (FE) method, the static characteristics, such as the flux density, PM flux linkage, back-EMF, cogging torque, and electromagnetic torque for the three stator structures are investigated. The influence of the design parameters on the electromagnetic torque is analyzed. The AFFSPMM with PPPS topology has the larger torque, lower cogging torque, and more sinusoidal back-EMF. The prototype with PPPS structure is built and tested. The experimental results are in agreement with the 3-D FE analysis.

Cogging Torque Analysis of Novel Dual-Rotor Axial Field Flux-Switching Permanent Magnet Machine

The cogging torque of a novel dual-rotor axial field flux-switching permanent magnet (DRAFFSPM) machine is investigated in this paper. The analytical equation of the DRAFFSPM machine is deduced. Based on 3D finite element method, the influences of the design parameters on the cogging torque are analyzed. The H-shaped stator tooth with slot chamfer is proposed and the slot opening width and chamfer thickness are optimized to reduce the cogging torque. It shows that the cogging torque is the minimum when the stator tooth width and stator magnet width equal to 8o and 7.5o mech., respectively. The cogging torque can be reduced by ~64% when the rotor pole width is 1.6 times that of the original design. The cogging torque can be reduced by ~80% when the chamfer is added in the stator slot.

Static Characteristics Analysis and Experimental Study of a Novel Axial Field Flux-Switching Permanent Magnet Generator

A novel axial field flux-switching permanent magnet (AFFSPM) machine with a doubly-salient structure is developed as a wind power generator. The electromagnetic characteristics of a 0.6 kW, 3-phase 12/10-pole AFFSPM machine, including the air-gap flux density distribution, open-circuit flux linkage, EMF, and winding inductances, etc., are investigated based on 3-D finite element (FE) analysis. A prototype is built to test the characteristics under both open-circuit and load conditions. The theoretical analysis is validated experimentally. It shows that the phase EMF is essentially sinusoidal, and the machine can not only be used as a wind power generator, but also as a permanent magnet brushless AC motor.

Novel Dual-Rotor Axial Field Flux-Switching Permanent Magnet Machine

A dual-rotor axial field flux-switching permanent magnet (DRAFFSPM) machine is proposed. A 3-phase 12/10-pole DRAFFSPM machine is designed. The topology and operation principle of the machine are described in detail. The power equation is deduced and the dimensions of the DRAFFSPM machine are determined. The electromagnetic characteristics including the air-gap field distribution, the PM flux-linkage, the back-EMF, and the cogging torque, are investigated based on the 3-D finite element (FE) analysis. The influences of the rotor pole width and the stator slot chamfer on the back-EMF and cogging torque are investigated. It shows that the sinusoidal back-EMF can be gained and the cogging torque can be greatly reduced.

A Novel Axial Field Flux-Switching Permanent Magnet Wind Power Generator

A novel axial field flux-switching permanent magnet (AFFSPM) machine with a doubly-salient structure is presented as a wind power generator. One rotor is sandwiched between two stators in which both windings and permanent magnets are placed. This novel generator is suitable for the wind power generation system because of its shorter axial length and higher power density. A three-phase 12/10-pole 0.6 kW AFFSPM generator is designed. The power-size equation of the machine is deduced, and the size of generator is determined. Based on the 3-D finite element method, the electromagnetic performances of the generator are investigated. According to the theoretical calculation, a prototype is manufactured and the experiments are done. The analysis results are consistent with the experimental ones well.