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In order to solve the problem of large eddy current losses and high temperature rises caused by a large number of permanent magnets, a new type of combined-magnetic-pole permanent magnet motor is proposed in this paper. The sinusoidally distributed subdomain model of a non-uniform-air-gap rotor was established using the Laplace equation, and the analytical expression of eddy current losses in the rotor in a uniform air gap and non-uniform air gap was derived. The effect of the rotor's eccentricity on eddy current losses was obtained. According to the characteristics of the distributed winding of the non-uniform-air-gap combined-pole permanent magnet motor, an equivalent treatment was performed to obtain the equivalent thermal conductivity value; to establish an equivalent thermal network model of the motor; determine the temperature of each component of the motor; and verify the correctness of the thermal network model through magnetothermal bidirectional coupling. Finally, an experimental platform was set up to carry out temperature rise experiments on the two prototypes. The experimental results show that a non-uniform-air-gap rotor structure can effectively reduce a rotor's eddy current losses and motor temperature rise, as well as verify the accuracy of the analytical model's calculation results. [ABSTRACT FROM AUTHOR]

This paper proposes a multi-sided permanent magnet linear synchronous motor (MSPMLSM) with Ring Structure Winding to meet the high thrust requirements of intelligent circular conveying systems. This motor adopts a three-sided mover structure with three working air gaps: the upper and lower air gaps are composed of parallel permanent magnets and fan-shaped primary teeth, resulting in incomplete primary-mover coupling; the side air gap consists of a Halbach permanent magnet array and arc-shaped primary teeth, leading to uneven air gap length. Firstly, this paper analyzes the magnetic field generated by the special air gap and derives the thrust expression. To simplify the optimization process, the motor is divided into two parts for optimization: Motor I is composed of the side mover and primary, and Motor II is composed of the upper and lower movers and primary. After performing a sensitivity analysis on the main structural parameters of Motor I, a hierarchical optimization is conducted using central composite design (CCD) and box-Behnken design (BBD), and the final parameters are determined using the Non-dominated sorting genetic algorithm II (NSGA-II). For Motor II, the mover parameters are determined through single-objective optimization. Finally, Motors I and II are combined and validated through finite element simulation, with results showing that the new motor significantly improves thrust performance.

In order to solve the problem of large eddy current losses and high temperature rises caused by a large number of permanent magnets, a new type of combined-magnetic-pole permanent magnet motor is proposed in this paper. The sinusoidally distributed subdomain model of a non-uniform-air-gap rotor was established using the Laplace equation, and the analytical expression of eddy current losses in the rotor in a uniform air gap and non-uniform air gap was derived. The effect of the rotor’s eccentricity on eddy current losses was obtained. According to the characteristics of the distributed winding of the non-uniform-air-gap combined-pole permanent magnet motor, an equivalent treatment was performed to obtain the equivalent thermal conductivity value; to establish an equivalent thermal network model of the motor; determine the temperature of each component of the motor; and verify the correctness of the thermal network model through magnetothermal bidirectional coupling. Finally, an experimental platform was set up to carry out temperature rise experiments on the two prototypes. The experimental results show that a non-uniform-air-gap rotor structure can effectively reduce a rotor’s eddy current losses and motor temperature rise, as well as verify the accuracy of the analytical model’s calculation results.

Thrust ripple and density greatly impact the performance of the linear machine and other linear actuators, causing positioning control precision, dynamic performance, and efficiency issues. Generalized pole-pair combinations are difficult to satisfy both the thrust and ripple for double salient reluctance linear machines. In this paper, a DC-Biased vernier reluctance linear machine (DCB-VRLM) is proposed to solve the abovementioned issues. The key to the proposed design is to reduce the ripple and enhance the thrust density with non-uniform teeth by utilizing and optimizing the modulated flux in the air gap. To effectively verify the proposed design, the DCB-VRLMs with different winding pole pairs and secondary poles are compared. The 12-slot/10-pole combination is chosen to adopt a non-uniform air gap structure. Moreover, the energy distribution of AC/DC winding is studied and optimized to further enhance the performance of the proposed DCB-VRLM. The results indicate that the DCB-VRLM with the non-uniform air gap has a lower thrust ripple, better overload capability, and higher thrust density, which confirms its superiority in long-stroke linear rail transit and vertical elevator applications. [ABSTRACT FROM AUTHOR]

In this paper, at first, a 24/16 three-phase switched reluctance motor is designed, then the rotor poles shape tips corrected for reduction ripple of single-phase torque waveform. By doing this, the single-phase torque waveform has a flat surface and consequently, the single-phase torque ripple is reduced. Also, due to the commutation between the machine phases, the torque drops during this time, which are known as torque pits. To reduce the ripple torque at these points, which requires overlap between the two successive phases of the machine, the pulse width of the excitation of the machine phases is adjusted. Comparisons have been made between two types of direct current excitation and chopped current (with different pulse widths). The results show that for constant pulse width under chopped current, applying the arc and modifying the shape of the rotor poles can reduce the torque ripple by 3.4%. Also, by applying chopped current control, the torque ripple was reduced by 46.7% compared to its conventional design structure.

To reduce the torque ripple, this study investigates the effect of different slot/pole ratios and air gaps on the torque ripple of the motor. Under the same size, same speed, and the same excitation, the performance analysis of the electric excitation concentrated winding motor with 12/10, 18/10, 30/10 is carried out. First, the finite element analysis of the motors with different slot/pole ratios is performed and the influence of the uniformity of the air gap of the motors on the cogging torque is comparatively analyzed. Through comparison, it is found that an appropriate slot/pole ratio can reduce cogging torque and the harmonic content of back EMF, and from the perspective of cogging torque, fractional slot motors are lower than integer slot motors. The use of non-uniform air gap can reduce the content of air gap magnetic density harmonics, therefore further reducing cogging torque and torque ripple. After finite element calculation, the inductance of these three kinds of motors and their influence on torque are analyzed. Finally, it is found that the non-uniform air gap has a more obvious effect on reducing the torque ripple of the motor. The torque ripple percentage of the 12/10 motor has been reduced from 10.6% to 4.2%. [ABSTRACT FROM AUTHOR]

Thrust ripple and density greatly impact the performance of the linear machine and other linear actuators, causing positioning control precision, dynamic performance, and efficiency issues. Generalized pole-pair combinations are difficult to satisfy both the thrust and ripple for double salient reluctance linear machines. In this paper, a DC-Biased vernier reluctance linear machine (DCB-VRLM) is proposed to solve the abovementioned issues. The key to the proposed design is to reduce the ripple and enhance the thrust density with non-uniform teeth by utilizing and optimizing the modulated flux in the air gap. To effectively verify the proposed design, the DCB-VRLMs with different winding pole pairs and secondary poles are compared. The 12-slot/10-pole combination is chosen to adopt a non-uniform air gap structure. Moreover, the energy distribution of AC/DC winding is studied and optimized to further enhance the performance of the proposed DCB-VRLM. The results indicate that the DCB-VRLM with the non-uniform air gap has a lower thrust ripple, better overload capability, and higher thrust density, which confirms its superiority in long-stroke linear rail transit and vertical elevator applications.

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In this paper, at first, a 24/16 three-phase switched reluctance motor is designed, then the rotor poles shape tips corrected for reduction ripple of single-phase torque waveform. By doing this, the single-phase torque waveform has a flat surface and consequently, the single-phase torque ripple is reduced. Also, due to the commutation between the machine phases, the torque drops during this time, which are known as torque pits. To reduce the ripple torque at these points, which requires overlap between the two successive phases of the machine, the pulse width of the excitation of the machine phases is adjusted. Comparisons have been made between two types of direct current excitation and chopped current (with different pulse widths). The results show that for constant pulse width under chopped current, applying the arc and modifying the shape of the rotor poles can reduce the torque ripple by 3.4%. Also, by applying chopped current control, the torque ripple was reduced by 46.7% compared to its conventional design structure. [ABSTRACT FROM AUTHOR]

This paper presents a characteristics analysis and performance comparison of high-speed two-phase 4/2 and hybrid single-phase 4/4 switched reluctance motors (SRMs). Although the motors are advantageous as high-speed drives, both conventional structures have high torque ripple as a result of the presence of the torque dead zone. In this paper, solutions to the torque dead zone problem for each motor are discussed. For the 4/2 SRM, a wide-rotor stepper-type is adopted, while for the 4/4 SRM, the structure is changed to a hybrid by adding permanent magnets (PMs). Both motors have a non-uniform air gap to modify their inductance profile, which leads to the elimination of the torque dead zone. A finite-element method was used to analyze the characteristics of each motor. Then, the manufactured motors were tested through experiments, and lastly, their performance was compared. [ABSTRACT FROM AUTHOR]

This paper presents a characteristics analysis and performance comparison of high-speed two-phase 4/2 and hybrid single-phase 4/4 switched reluctance motors (SRMs). Although the motors are advantageous as high-speed drives, both conventional structures have high torque ripple as a result of the presence of the torque dead zone. In this paper, solutions to the torque dead zone problem for each motor are discussed. For the 4/2 SRM, a wide-rotor stepper-type is adopted, while for the 4/4 SRM, the structure is changed to a hybrid by adding permanent magnets (PMs). Both motors have a non-uniform air gap to modify their inductance profile, which leads to the elimination of the torque dead zone. A finite-element method was used to analyze the characteristics of each motor. Then, the manufactured motors were tested through experiments, and lastly, their performance was compared.

The magnetic characteristics of a Switched Reluctance Motor (SRM) in normal and abnormal conditions are important in performance prediction and verification of the motor. In this paper, a novel view of air gap magnetic field analysis of SRM under rotor misalignment is presented. This analysis is based on a three-dimensional finite element method (FEM) to provide the precise fault diagnosis. This method is used to simulate reliable and precise model by considering the end effects as well as axial fringing effects. The FE analysis are performed to obtain the static magnetic characteristics of SRM including flux linkages, terminal inductance and static torque profile under different rotor positions for varying degree of misalignments. To do so, Fourier analysis is carried out to study the variations of diagnosis index. Inductance waveforms were analyzed by FFT, and the concept of relative spectral coefficient from the FFT analysis is given as a fault diagnosis index, and its sensitivity to SRM misalignment fault is shown under different conditions. The obtained results present useful information with regard to the detection as well as the amount of misalignment fault. To the best knowledge of the authors, such an analysis has not been carried out previously. [ABSTRACT FROM AUTHOR]