An IPMSM with I2V type rotor topology structure is proposed, its loss, efficiency and torque are analyzed and compared with V and IV type. Firstly, the optimized rotor topology structures are used to analyze the no-load air-gap flux density waveform and harmonic contents of the IPMSM. The results show that the THD of the no-load air-gap flux density with the I2V type is the smallest and the sinusoidal degree of the waveform is the highest. Secondly, the loss of the IPMSM with optimized rotor topology structures are analyzed and compared. Compared with the other two rotors, the results show that the iron loss of the IPMSM with the I2V type is the smallest. The iron loss of the IPMSM with I2V type is significantly less than that of the other two rotors especially under the deep flux weakening conditions. The output torque of the IPMSM under different current angles, current densities and speed are analyzed and compared. The results show that the torque performance of the IPMSM with I2V type is better than the other two rotors. this paper proposes a simple and effective method to optimize the position and diameter of the magnetic isolation holes by establishing a parameterized model. The results show that the torque ripple and cogging torque with the further optimized I2V type rotor topology structure are greatly reduced, the iron loss and magnet loss are also effectively reduced. Finally, the von Mises stress and the total displacement of the rotor deformation of the IPMSM with the further optimized I2V type under different working conditions are verified by finite element analysis. The results show that the rotor will not rupture, the displacement is small enough to avoid the touch between stator and rotor.

An interior permanent magnet synchronous motor (IPMSM) with ‘VV—’ shape rotor topology structure is proposed. The established two‐dimensional (2D) parameterized finite element analysis (FEA) models are used to analyze and compare the output average torque, torque density, air‐gap flux density and back electromotive force (EMF) of the IPMSM with ‘V’ shape, ‘V—’ shape, ‘VV—’ shape for electric vehicle (EV) applications. The rotor topology structure has a great influence on the performance of the IPMSM, especially the first layer of permanent magnet of the multi‐layers permanent magnet structure has the greatest influence on the performance of the IPMSM. Therefore, firstly, this paper mainly analyzes and optimizes the opening angle of permanent magnet and the pole arc angle of the first layer, which have a great influence on the electromagnetic performance of the IPMSM. Secondly, the d ‐axis and q ‐axis inductance, saliency ratio, output average torque, reluctance torque under different current angles are analyzed and compared. The results show that the output average torque and reluctance torque of the IPMSM for EV applications with ‘VV—’ shape rotor topology structure proposed in this paper are larger than that of the other two rotor topology structures as the amount of permanent magnet with ‘VV—’ shape rotor topology structure is slightly reduced. Finally, the torque density versus current density of the IPMSM with three different rotor topology structures is analyzed and compared. The results show that the torque density of the IPMSM with ‘VV—’ shape proposed in this paper is higher than that of the other two rotor topology structures under different current densities.

The high magnetic saturation at flux isolation bridge of interior permanent magnet synchronous motor (IPMSM) enriches the harmonic content of air gap flux density. When IPMSM operates at low speeds, these harmonics of air gap flux density increase torque ripple. An IPMSM with I2V type is proposed to further improve sine degree of no-load air gap flux density, achieving high torque density and low torque ripple. The V type, IV type and I2V type are selected as the comparative objects for optimization research, the established 2D parameterized finite element analysis (FEA) models are used to optimize and analyze opening angle and pole arc angle of the first layer of permanent magnet, which have the greatest impact on the electromagnetic performance of IPMSMs. Under the constraint of same volume of permanent magnets, the optimization models of three different rotor structures are determined ultimately. The no-load air gap flux density waveforms and harmonic contents of IPMSM with three different optimized rotor topology structures are analyzed and compared, the results show that the no-load air gap flux density of I2V type proposed in this paper have the lowest total harmonic distortion rate (THD).The torque performances are analyzed and compared with the other two, the results show that torque performances of I2V type are superior to the other two as the amount of permanent magnet is slightly reduced. Aiming at problems that the torque ripple of I2V type is greater than the other two under rated operating conditions, this paper proposes a simple and effective method to add a set of circular flux isolation holes under each pole of the rotor, and the position and diameter of flux isolation holes are adjusted to further optimize the magnetic circuit in order to reduce torque ripple. The optimization results showed that reduction ratio of torque ripple with optimized I2V type is 67.3% under rated operating conditions. The I2V prototype is processed and manufactured and a prototype experimental platform is built. Experimental verifications are conducted on the torque, external characteristics. The test results are basically consistent with the FEA results, proving the accuracy of the analysis and modeling, as well as the effectiveness of simulation calculations in this paper.

Interior permanent magnet synchronous motor (IPMSM) has advantages with high power density, wide speed range, small size, and high efficiency, and is widely used in the drive system of electric vehicles. Compared to other types of motors, permanent magnet synchronous motors (PMSMs) have some irreplaceable advantages, but there are also some disadvantages. As a type of PMSM, IPMSMs have problems with large fluctuations in permanent magnet (PM) magnetic field and demagnetization. At present, irreversible demagnetization of PMs is the most serious problem faced by IPMSMs. Once irreversible demagnetization of PMs occurs, it can cause a decrease in the performance of IPMSMs and can even damage the entire drive system. This paper takes an IPMSM with 48 slots, 8 poles, and 66 kW as the research object. Based on the reasons for PM demagnetization, a PM demagnetization model is established to obtain the demagnetization law of PMs. Firstly, the magnetic properties of PM materials were described based on their characteristic curves. The demagnetization mechanism of PMs was analyzed, and the demagnetization process of PMs was studied in combination with the reasons for demagnetization. Secondly, the basic parameters and torque performance of IPMSMs were calculated and analyzed. We analyzed the demagnetization curves of PM materials at different temperatures, calculated the operating points of PMs under various working conditions, and analyzed whether PMs undergo irreversible demagnetization based on the relationship between the operating points of PMs and the knee points of demagnetization curves. A high-fidelity electromagnetic–thermal coupling simulation model has been established, combined with the characteristics of electric vehicle driving conditions, to accurately characterize the temperature rise distribution and electromagnetic parameter changes of IPMSMs under different operating conditions and achieve multi-physics field collaborative analysis. Finally, a finite element model is adopted to simulate uniform and local demagnetization of PMs, and the changing characteristics of motor performance parameters under demagnetization are summarized. Different magnitudes of d-axis reverse current are applied as demagnetization excitation to analyze PM behaviors under various demagnetization degrees. The variations in magnetic flux density, output torque, and no-load back electromotive force (EMF) before and after demagnetization are simulated and analyzed. For the investigated motor and specific magnet grade, this work summarizes the irreversible demagnetization characteristics and corresponding practical judgment references.

The fractional-slot, concentrated-winding, interior permanent magnet synchronous motor (FSCW IPMSM) has advantages, such as reducing motor copper consumption, improving flux-weakening capability, and motor fault tolerance, and has certain development potential in application fields such as electric vehicles. However, fractional-slot concentrated-winding motors often contain rich harmonic components due to their winding characteristics, leading to increased motor losses and back electromotive force harmonics, thereby affecting the efficiency and constant power speed regulation range of the motor. Based on this, this article first uses the winding function method to explore the inductance and saliency ratio of the interior permanent magnet synchronous motor with different slot pole combinations in the fractional-slot concentrated- winding of electric vehicles. Secondly, this article will establish a 2D finite element parameterized model to analyze and compare the performance of fractional-slot concentrated-winding motors with different slot pole combinations, including air gap magnetic density, back electromotive force distortion rate, overload multiple, and torque. The structural parameters of the motor were optimized with the objective of minimizing the torque ripple under the constraint of minimizing the average torque reduction. The motor slot width, permanent magnet angle, and permanent magnet pole arc angle were analyzed and optimized. The simulation results showed that 12 slots and 8 poles were the optimal design schemes, providing a theoretical basis for the selection of slot pole coordination in the fractional-slot concentrated-winding interior permanent magnet synchronous motor for electric vehicles.

Iron loss of stator is one of the main losses of interior permanent magnet synchronous motor (IPMSM). Therefore, effectively reducing iron loss is of great significance for improving operating efficiency. The air gap flux density is analyzed under various operating conditions, and three models for calculating iron loss are analyzed and compared. Among these, the orthogonal decomposition model demonstrates greater accuracy and is relatively straightforward to apply. Consequently, this paper utilizes the orthogonal decomposition model for iron loss calculations. Iron loss is primarily influenced by the operating frequency, as well as the amplitude and harmonic content of the air gap flux density. Thus, at a specific frequency, enhancing the sine degree of the air gap flux density can significantly decrease iron loss. A three-layer I2V type is proposed to further improve sine degree of air gap flux density, achieving high efficiency and low iron loss. V type, IV type and I2V type are selected as the comparative objects for optimization research, and air gap flux density and harmonic contents of three different rotor structures are analyzed and compared, the results show that I2V type have the lowest total harmonic distortion (THD) rates. Compared with V type, the THD rates of I2V type decreased by 27.2%. Iron losses of three different optimized rotor structures are analyzed and compared. Compared with the other two, the results show that I2V type is the smallest, and is significantly less than that of the other two especially under deep flux weakening conditions, which can improve operation range of high efficiency. The I2V prototype is processed and manufactured, and experimental platform is built. Experimental verifications are conducted on loss and efficiency. The test results are basically consistent with FEA results, proving the superior performance of I2V type proposed in this paper, as well as correctness of analysis method and effectiveness of simulation calculations.