Torque Density Elevation in Concentrated Winding Interior PM Synchronous Motor With Minimized Magnet Volume

Permanent magnet synchronous motors (PMSMs) have been extensively adopted in a range of industrial applications, particularly in the electric vehicle industry, due to their high power and torque density, high efficiency, reliability, and excellent dynamic performance. Between the types of PMSMs, a surface-mounted PMSM (SPMSM) is characterized by identical <i>d</i>- and <i>q</i>-inductances, due to which it only generates magnetic torque. However, SPMSMs also exhibit higher flux density, since the air gap in these motors is smaller and the permanent magnets are located very close to the stator teeth. In contrast, an interior PMSM (IPMSMs) features different <i>d</i>-axis and <i>q</i>-axis inductance components, due to which it can create not only magnetic torque but also reluctance torque. In this paper, two processes are conducted to examine these motors. First, an analytical technique is proposed to design the required parameters for an SPMSM and an IPMSM, where the dimensions of the latter are defined using the fractional-slot concentrated winding configuration, and those of the former are designed based on the approach of keeping the rotor volume, permanent magnet volume, pole–slot combination, and power supply unchanged. Subsequently, a finite element method is presented for computing, simulating, and comparing the electromagnetic parameters of both proposed motors, including their back electromotive force, torque ripple, efficiency, and power factor. Finally, the proposed methods are validated using a 7.5 kW practical motor.

For electric vehicles (EVs), permanent magnet synchronous motors (PMSMs) are competitive owing to their high power factor, high efficiency and high power density. In this paper, four types of PMSMs with different rotor topologies are designed with the same motor main dimensions and the same amount of permanent magnet usage. First, the different PMSMs are compared in terms of their torque characteristics. The torque characteristic curves of the four motors are displayed with the control method i <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> =0 for surface-mounted PMSM (SPMSM) and Maximum Torque per Ampere (MTPA) for interior PMSM (IPMSM). It turns out that IPMSM has higher starting torque than SPMSM due to the reluctance torque. Among the three IPMSMs with different rotor structures, V-shape IPMSM and delta-shape IPMSM can provide higher output torque under the same current supply with the higher salient rate. More information on the no-load magnetic density, torque ripple, efficiency and demagnetization problem operated at the peak current is also provided and compared. Then the four PMSMs with the same peak current are further analyzed and compared on the flux-weakening speed-enlarge (FWSE) capability. The results show good FWSE capability for all of the four PMSMs owing to the large peak current. However, the torque of SPMSM in flux-weakening control region is slightly higher than the IPMSMs.

A new instantaneous torque-control strategy is presented for high-performance control of a permanent magnet (PM) synchronous motor. In order to deal with the torque pulsating problem of a PM synchronous motor in a low-speed region, new torque estimation and control techniques are proposed. The linkage flux of a PM synchronous motor is estimated using a model reference adaptive system technique, and the developed torque is instantaneously controlled by the proposed torque controller combining a variable structure control (VSC) with a space-vector pulse-width modulation (PWM). The proposed control provides the advantage of reducing the torque pulsation caused by the nonsinusoidal flux distribution. This control strategy is applied to the high-torque PM synchronous motor drive system for direct-drive applications and implemented by using a software of the digital signal processor (DSP) TMS320C30. The simulations and experiments are carried out for this system, and the results demonstrate the effectiveness of the proposed control.

This paper deals with theoretical analysis and design of permanent magnet (PM) synchronous motors (PMSMs) with minimized cogging force. Recently, many optimal designs for the PMSMs have been done by finite element (FE) analysis, but such analysis generally is time consuming. In this study, the equation of magnetic flux lines existing between PMs and iron cores is expressed geometrically and the cogging force is calculated theoretically without FE analysis. The form of equation is assumed to be the second-order polynomial and the virtual core is used to express the cogging force in analytical model. The cogging force can be calculated by applying the solved flux line equation and the flux density equation to the Lorentz force equation by using the Maxwell stress tensor. The theoretical analysis of minimized cogging force is applied to several prototypes such as synchronous PM planar motor (SPMPM), 2-DOF PMSM with screw motion, and axial flux PM (AFPM) brushless dc motor in this paper, and the analytical results are validated by FE analyses and experiments.

The increase of pole numbers of the interior permanent magnet (IPM) synchronous machine can boost its air gap flux density, raise its efficiency and torque, and reduce its volume and weight. With the help of geometry module, this paper analyzes the relation between "flux concentration function" and the pole pair numbers of IPM synchronous machine, discusses connections between pole numbers and air gap flux density, per pole flux, non-load electric potential, flux density of rotor lead magnet material, flux density of stator tooth, flux density of stator yoke, and power which permanent magnet of unit volume produce respectively. Finally, authors point out: (1) when the saturation of lead magnet material was considered, the air gap flux density and the sums of the per pole flux will produce a the maximum with the increase of pole pairs, that is, IPM machine has a suitable pole pairs; (2) IPM machine bears "flux concentration function", when its pole pairs is more than or equal to 3, B/sub /spl delta///B/sub M/>1 or 4, B/sub /spl delta///B/sub r/>1; (3) the pole pairs of the IPM machine, which be from 3 to 6, is suitable. (4) the inner flux density of permanent magnet and power produced by the permanent magnet of unit volume will drop with the increase of pole pairs of the IPM machine.

For avoiding the damage of the insulation and permanent magnet, the temperature rise of the PMSM (permanent magnet synchronous motor) should be controlled strictly, it is usually one of the main objectives during improving the output power and torque density beyond the state-of-the-art in motor design. In this research, the coolant channel will be placed within the yoke of the stator core to enhance the heat transfer between the stator core and the coolant. Hydrophobic coating is applied to replace the metal tube for increasing the utilization of the cross area of the coolant channel. The impact of the coolant channel on the performance of the permanent magnet motor is analyzed. A general design method of the coolant channel is presented. The result shows that the change of the stator core loss is within about 10% as the coolant channel is moved away from the slot along the radial direction while the back electromotive force of the motor could keep constant through appropriate design. The impacts of the coolant channels on the magnet performance and the heat dissipation performance could be divided completely with the design method. The method can be applied on various PMSM including SPM (surface-mounted permanent magnet motor) and IPMSM (interior permanent magnet synchronous motor). Sufficient coolant flow could be provide to help conduct the temperature rise of the motor.

The mechanism of torque ripple generation by time and space harmonic magnetic fields in permanent magnet synchronous motors is investigated to obtain advanced motor designs. The general expression between the torque ripples and harmonic air-gap flux densities in the motor is derived by using Maxwell stress tensor. Both the numerical and experimental verifications of this expression are carried out. By using this expression, the difference of the torque ripple generation between the surface and interior permanent magnet synchronous motors are discussed. Based on these investigations, the shape of the rotor surface of an interior permanent magnet motor is optimized. It is clarified that specific harmonic components of thetorque ripples in interior permanent magnet synchronous motors can be reduced to be nearly zero by optimizing the rotor surface shape.

<title>Abstract</title> Permanent Magnet Synchronous Motors (PMSMs) are increasingly adopted in electric vehicles (EVs) and industrial drives due to their high efficiency and torque density. However, performance varies with motor topology, operating conditions, and thermal management. This study presents a comparative evaluation of three PMSM types—Axial Flux, Interior Permanent Magnet (IPM), and Surface Permanent Magnet (SPM)—using a subset of 1,000 records from the PMSM Smart Control Dataset (Kaggle), containing 15 electrical and thermal parameters. Statistical analysis and comparative plots were used to examine efficiency, torque–speed characteristics, current and voltage demand, and temperature rise under different load conditions, cooling methods, and application modes. Results show that SPM motors achieve the highest efficiency (75.9%) and superior thermal stability, making them suitable for sustained EV traction, while IPM motors provide strong torque density and wide-speed performance. Axial Flux motors, with compact geometry and steady torque, are most advantageous in constant-torque industrial drives. In addition, predictive modeling was employed to estimate efficiency from electrical, thermal, and categorical descriptors. A linear regression model achieved R² ≈ 0.62 on the test dataset, with stator/rotor temperatures, current, and operating mode identified as the most influential predictors. These findings demonstrate that combining comparative evaluation with predictive modeling supports optimal PMSM selection and enables lightweight, real-time efficiency estimation, contributing to intelligent control strategies for sustainable mobility

Synchronous homopolar motors (SHMs) with an excitation winding located at the stator and a toothed salient pole rotor are a good alternative to motors traditionally used in traction applications such as induction motors or interior permanent magnet synchronous motors (IPMSM). This study presents the results of a theoretical comparison between an IPMSM and an SHM in a traction application with a constant power speed range of 1:10, which is specific to the mining truck drives, and with a rated power of 370 kW. The considered IPMSM and SHM have the same number of phases, poles and stator slots, and the same outer diameter of the stator lamination. The IPMSM design is optimized using the Nelder–Mead method. The main objectives of optimization are to minimize the average losses in the operating cycle and to limit the required power of the semiconductor inverter. The performance of the optimized IPMSM is compared with the previously obtained performance of the SHM optimized by the same method. Although the average losses in the operating cycle in the compared motors are approximately equal, the losses at high speed for the IPMSM are about two times greater than at low speed with maximum torque, which means that there is a need to intensify the IPMSM cooling system and there is deterioration of reliability. The advantage of the IPMSM is the reduction in the length of the active part by 30%. The advantage of the SHM is that there is 4.6 times lower cost of active materials. In addition, the SHM is more reliable than the IPMSM, as there is no risk of overheating, demagnetization or degradation of permanent magnets over time.

The spoke type permanent magnet synchronous motor (PMSM), which is a general ferrite magnetic flux concentrated motor, has a low portion of reluctance torque at the total torque magnitude. Therefore, as a way to increase the reluctance torque, there is a double-layer spoke type PMSM that can maximize the difference in inductance between the d-axis and the q-axis. However, in the double-layer spoke type PMSM, cogging torque, torque ripple, and total harmonic distortion (THD) increase as reluctance torque is maximized, which is the main cause of vibration and noise. In this paper, a method is proposed that provides the same effect as skew without dividing stages of the permanent magnet by dividing the core of the rotor into two types so that it is easy to manufacture according to the number of stages unlike extant skew methods. Based on the method, the reduction of cogging torque and THD was verified by Finite Element Analysis (FEA).1. IntroductionThe general interior permanent magnet synchronous motor (IPMSM) uses NdFeB magnets to take advantage of the high airgap magnetic flux density. However, it had an adverse impact on cost of the motor because there are fluctuation of the cost from limited sources of heavy rare earth. Therefore, for stable supply of permanent magnets, a lot of development of a spoke type permanent magnet synchronous motor (PMSM), which is a structure capable of concentrating magnetic flux by using a ferrite magnet having a low magnetic flux density, has been conducting. The spoke type PMSM concentrates the magnetic flux density and can replace the NdFeB magnet used in the extant PMSM with a ferrite magnet.However, in general spoke type PMSM, the portion of reluctance torque is low because the difference in inductance between the d-axis and the q-axis is not large. In order to further utilize this reluctance torque, a double-layer spoke type shape that can maximize the difference in inductance between the d-axis and the q-axis can be used to bigger reluctance torque to improve motor performance.However, increasing the reluctance torque increases cogging torque, torque ripple, and total harmonic distortion (THD), which in turn leads to vibration and noise problems. Therefore, the double-layer spoke type PMSM needs a design that can reduce cogging torque and THD. As a representative method, it can be solved by applying skew to the rotor, but the conventional method of applying skew is not a good method in terms of productivity because it is difficult to manufacture because it divides the stages of the permanent magnet. For ameliorate of the limitation, the shape of the rotor core is divided and cross-stacked into stack1 and stack2 so that the permanent magnet can be inserted in one shape as the conventional shape.Therefore, the shape of the rotor core is divided into stack1 and stack2 so that the permanent magnet can be inserted in one shape as before and cross-stacked. The stack1 cuts the left part fixing the permanent magnet, and the stack2 cuts the right part fixing the permanent magnet to apply the same effect as skew. In this paper, this is expressed as a core skew, and through this core skew, the design to reduce cogging torque, torque ripple, and THD is conducted while considering productivity.2. Concept of Core SkewThe core skew represents the stacking of only cores of opposite shapes when stacking the rotor cores of the motor. The contents of the basic theory are as follows.Fig. 1 shows stack No. 1 and stack No. 2, respectively. Due to the shape of the rotor core, the phases of the airgap magnetic flux density of stack No.1 and stack No.2 are shifted, and when the two stacks are synthesized due to the phase of the shifted airgap magnetic flux density. As shown in Fig. 2, the cogging torque decreases.Also Fig. 1 shows the shape of applying core skew to the conventional model by intersecting and stacking stack No. 1 and stack No. 2 .Through this core skew structure, research to reduce cogging torque, torque ripple, and THD is conducted. Most of the original skew research is conducted in 3D FEA, but since 3D FEA requires a lot of time, first calculate the optimal model using 2D FEA and then proceed with 3D FEA according to the number of steps considering 3D effect. The final result will be revealed on full paper.AcknowledgmentThis work was supported by the Technology Innovation Program (No. 20011495) funded By the Ministry of Trade, Industry & Energy(MOTIE, Korea), in part by the National Research Foundation of Korea (NRF) Grant funded by the Korean government. (No. 2020R1A2C1013724). **

Recurrent modified Elman neural network control of PM synchronous generator system using wind turbine emulator of PM synchronous servo motor drive

The manufacturing tolerance of the permanent magnets (PMs) is inherent in the produce of the machine. These tolerances influence back electromotive force (EMF), which is an important response of the motor. In order to enhance the quality of the product, the authors need to reduce these tolerances, but it is very difficult and involves a number of costs. Therefore, this study presents a robust design of the EMF characteristic analysis considering the manufacturing tolerances of PM in the interior PM synchronous motor (IPMSM). Among the robust optimisation method, Taguchi robust design based on orthogonal array was applied. Finally, the validity of the analysis result is verified by comparing the optimum design model with present design model (mass production model) ones.

This paper presents a sliding mode controller for an interior permanent magnet (IPM) synchronous motor, in which direct torque control (DTC) concept, variable structure control and space vector modulation (SVM) are integrated to achieve high performance. In comparison with conventional DTC, the inverter switching frequency is constant and controllable by using SVM, the torque and flux ripple are significantly reduced. The fast response and robustness merits of DTC are preserved. Position and angular speed of the rotor are obtained through an extended Kalman filter (EKF).

In order to estimate the vibration and acoustic noise in a permanent magnet (PM) synchronous motor, the natural frequencies of the stator structure should be determined during the design stage. In this paper, analytical formulas to predict the natural frequencies of the stator are derived. The analytical model of the stator includes stator teeth, winding, stator core, and stator case. It is observed that the natural frequencies calculated with the integrated components exceed those based on the stator core alone only. In order to verify this analytical model, numerical simulation and experimental measurement are carried out using a PM synchronous motor which has 5 pole-pairs and 12 slots structure configuration. Good agreements are observed among the results obtained by analytical formula, simulation and experiment.

Recently, means of transportation with electrical motors such as electric vehicles and ships are rapidly increasing. Various attempts have been made to reduce the size of the motors to increase the freedom of transport equipment system layouts and the energy efficiency of their transportation. Interior permanent magnet synchronous motors (IPMSMs) can realize higher torque than surface permanent magnet synchronous motors (SPMSMs) by using reluctance torque caused by magnetic saliency in addition to magnet torque. In comparison with SPMSMs, IPMSMs can have wide operation ranges by applying control methods such as maximum output control and field weakening control. Therefore, IPMSMs are expected to be used for a variety of application such as electric vehicles, ships and heavy equipment. By replacing permanent magnets with bulk superconductors in the rotors of IPMSMs, the magnet torque increases due to the stronger magnetic field of magnetized bulk superconductors. This leads to an increase in total torque density of the motors and contributes to motor size reduction. In this research, we propose an IPMSM with bulk superconductors with the goal of increasing the mechanical output density. In the proposed IPMSM, cooling space is left inside the rotor to cool the bulk superconductors to their superconducting state. Here, analysis based on finite element method was carried out to verify the utility of the proposed motor. First, the design of the motor with bulk superconductors and cooling space is discussed. It is shown that the total torque can be increased by adjusting the position of the bulk superconductor and modifying the structure of the flux barrier. The maximum total torque shown here was 22500 Nm. Then, the mechanical output density of the proposed IPMSM is compared with a conventional IPMSM. It is shown that the mechanical output density of the proposed IPMSM is 38% higher than the conventional IPMSM. Finally, the magnetic shielding effect, which might be a problem when using bulk superconductors, is discussed. By using electromagnetic analysis, it is shown that the external magnetic flux is weakened by the cooling space to several percent of the magnets’ surface and the effect of the shielding current is trivial.