Interior Permanent Magnet Motor Research Articles

Electromagnetic-thermal-mechanical performance of novel interior permanent magnet motor

To mitigate the challenges of magnetic leakage and iron loss in the rotor of interior permanent magnet (IPM) motors, this article proposes a novel rotor structure that eliminates the bilateral bridge, relying solely on a central bridge to maintain rotor strength. This design reduces the overall bridge width of the rotor, thereby decreasing magnetic leakage and improving torque. The novel rotor features a distinctive design that combines high silicon steel sheets and low silicon steel sheets. High silicon steel sheets are used on the rotor's surface to minimize iron loss, while low silicon steel sheets are used internally to ensure rotor strength. This design takes advantage of the high silicon steel's low iron loss while mitigating its brittleness and saturation issues. The article describes the method for producing this combined rotor. Mechanical and electromagnetic property tests are conducted on both high and low silicon steel sheets, resulting in stress-strain curves, B-H curves, and iron loss characteristics. Finally, the rotor stress is calculated. The analysis indicates that this novel motor can reduce magnetic leakage, increase torque by 7.5 %, improve efficiency by 0.18 %, decrease rotor iron loss by 36.2 %, and lower rotor temperature by 3.9 % compared to the original motor.

Flux-Oriented Design and Analysis of a Hybrid Rotor Pole Interior Permanent Magnet Motor for In-Wheel Direct Drive

Flux-Oriented Design and Analysis of a Hybrid Rotor Pole Interior Permanent Magnet Motor for In-Wheel Direct Drive

Design and Experiment of Post-Assembly Magnetization System for a 160-kW Interior Permanent-Magnet Motor

Design and Experiment of Post-Assembly Magnetization System for a 160-kW Interior Permanent-Magnet Motor

Electromagnetic Optimization of a High-Speed Interior Permanent Magnet Motor Considering Rotor Stress

High-speed interior permanent magnet (IPM) motors require highly reliable rotors. Some measures must be adopted to improve rotor safety, but its electromagnetic performance is seriously affected. It is a challenge to achieve excellent electromagnetic characteristics while satisfying mechanical strength. This paper presents an electromagnetic optimization design of high-speed IPM motors considering rotor stress. Firstly, the permanent magnet (PM) is segmented by adding stiffeners to improve stress distribution. The effects of the bridge and stiffener thickness on the rotor stress and electromagnetic performance are analyzed. Secondly, an electromagnetic optimization model is built based on a three-segment PM rotor structure, aiming for maximum efficiency and minimum rotor core losses. Then, the initial design and optimized scheme are compared, the results show that the efficiency, safety and temperature performance of the motor are improved. Finally, a 140 kW, 18,000 rpm prototype is manufactured and tested. The above analysis provides a valuable reference for the design and widespread application of high-speed IPM motors.

Topology and parameter optimization of IPM motor considering mechanical strength by stress and connection constraints

PurposeThe purpose of this study is to apply the topology and parameter optimization (TPO) to interior permanent magnet (IPM) motors to obtain the optimized shape with higher torque, lower ripple and sufficient mechanical strength.Design/methodology/approachThe constraints regarding the maximum stress, connectivity and mesh quality were considered to achieve not only high electrical performance but also high mechanical strength. To enhance the accuracy of the finite element analysis of the elastic analysis, this paper used body-fitted mesh adaptation technique to avoid the stress concentration.FindingsThe proposed method in this study resulted in feasible shapes with sufficiently high strength compared to previous studies. It is also shown that TPO yielded IPM motors with higher torque compared to topology optimization (TO) with fixed parameters.Practical implicationsDifferent from the existing studies on topology optimization of IPM motors, the mechanical strength is even considered by evaluating the stress values. Therefore, in the practical phase, geometries can be designed that are less likely to be damaged due to deformation, even in the high-speed rotation range.Originality/valueThis paper performed TO and parameter optimization (PO) simultaneously, considering not only the electrical performance but also the mechanical strength. Furthermore, the mechanical strength was evaluated more precisely by devising the elastic analysis conditions and mesh generation.

Comparison of Electromagnetic Performance in Interior Permanent Magnet Motors with Different Central and Bilateral Bridges

Studies on the central and bilateral bridges of interior permanent magnet (IPM) motors often focus on individual mechanical strength or electromagnetic performance, lacking comparative studies on the electromagnetic performance of motors with different central and bilateral bridges under the same mechanical strength. This paper designs three rotors with different central and bilateral bridges and compares the electromagnetic performance of the three motors. First, to ensure the safe operation of the three rotors at high speeds, the mechanical stress of each rotor has been analyzed using the finite-element method (FEM). Subsequently, the major electromagnetic performances of the three motors are analyzed and compared, including the air-gap flux density, back electromotive force (back-EMF), inductance, salience, torque, power, loss, efficiency, and demagnetization. The results indicate that the rotor without central bridges has the largest leakage flux and the lowest torque but exhibits minimal torque ripple. The rotor with narrower bilateral bridges has the highest torque and maximum torque ripple. The torque performance of the rotor with wider bilateral bridges lies between the two aforementioned motors, and it possesses the highest efficiency. In the end, by adjusting the dimensions of the permanent magnets, the torque of all three models increases, but the motor with narrower bilateral bridges still has the largest torque. These findings provide valuable references for rotor design.

Neural Network With Cloud-Based Training for MTPA, Flux-Weakening, and MTPV Control of IPM Motors and Drives

An interior permanent magnet (IPM) motor is a prime electric motor used in electric vehicles (EVs), robots, and electric drones. In these applications, maximum torque per ampere (MTPA), flux-weakening, and maximum torque per volt (MTPV) techniques play a critical role in the efficient and reliable torque control of an IPM motor. Although several approaches have been proposed and developed for this purpose, each has its specific limitations. The objective of this paper is to develop a neural network (NN) method to determine MTPA, flux-weakening, and MTPV operating points for the most efficient torque control of the motor over its full speed range. The NN is trained offline by using the Levenberg-Marquardt backpropagation algorithm, which avoids the disadvantages associated with online NN training. A cloud computing system is proposed for routine offline NN training, which enables the lifetime adaptivity and learning capabilities of the offline-trained NN and overcomes the computational challenges related to online NN training. In addition, for the proposed NN mechanism, training data are collected and stored in a highly random manner, which makes it much more feasible and efficient to implement lifetime adaptivity than any other methods. The proposed method is evaluated via both simulation and hardware experiments, which shows the great performance of the NN-based MTPA, MTPV, and flux-weakening control for an IPM motor over its full speed range. Overall, the proposed method can achieve a fast and accurate current reference generation with a simple NN structure, for optimal torque control of an IPM motor.

General 2-D Analytical Framework for No-Load Analysis of Interior Permanent Magnet Machines

Solving two-dimensional (2-D) Maxwell’s equations in interior permanent magnet (IPM) motors is fairly complex due to the asymmetrical geometry of rotor magnets in the cylindrical coordinate system. This paper presents a general imaging solution to enable the 2-D open-circuit modeling of the family of IPM machines. Interior magnets are replaced/modeled with (i) virtual magnets on the surface of the rotor body (mapping interior magnets to the surface of the rotor body), and (ii) virtual volume current on the surface of the rotor body. The specifications of the virtual magnet (i.e., the remnant flux density) and the virtual volume current (i.e., current density level) are determined via magnetic circuit model. Next, the 2-D flux distribution of the transformed machines are calculated by solving 2-D Maxwell’s equations and considering relevant boundary conditions. Meanwhile, the effect of stator slots on flux profile is accounted by injecting proper amount of surface magnetizing current on the stator bore. Analytical results are supported via finite element method (FEM) and a series of experimental measurements.

Enhancement of local anti-demagnetization ability of permanent magnet by selected area grain boundary diffusion toward high-speed motors

The working environment of permanent magnets in high-speed motors is harsh, because they are seriously affected by multi-physical fields such as temperature, stress, weak magnetic control field, etc., and irreversible demagnetization is easy to occur under the extreme working conditions. In this work, a model of high-speed Interior Permanent magnet Motor is established, the easy demagnetization area of the permanent magnet is simulated by electromagnetic and thermal simulations to determine, and its local anti-demagnetization optimization is performed. Dy/Tb co-infiltration is carried out in the easy demagnetization region of the permanent magnets, and the process of selective zone diffusion is analyzed based on the principle of selective zone grain boundary diffusion. Through microscopic observation and macroscopic magnetic performance test, the effect of local anti-demagnetization performance enhancement of the optimized permanent magnets is verified. The results show that the magnetic properties of the optimized permanent magnets are obviously improved after the optimization of the selected zones. The present approach is important for the follow-up less heavy-rare-earth research of permanent magnet and its application in high-speed motors.

Magnetic Field Prediction of U-Shaped Interior Permanent Magnet Motor Considering Magnetic Bridge Saturation

Magnetic Field Prediction of U-Shaped Interior Permanent Magnet Motor Considering Magnetic Bridge Saturation

Optimal Design of a Novel Consequent-Pole Interior Permanent Magnet Motor with Flared-Structured Rotor

Interior permanent magnet motors are widely used in applications requiring high power density and high efficiency due to their high torque-generating capabilities. Recently, given the price fluctuations and unstable supply of rare earth permanent magnets, alternative configurations with reduced use of permanent magnets are being sought. Among the various candidates related to this, the consequent-pole type rotor structure can halve the number of permanent magnets used compared with conventional structures. However, in a no-load analysis, the waveform of the back electromotive force becomes asymmetric, generating a harmonic component. As a result, there is a disadvantage that the torque ripple increases. To overcome these shortcomings, we propose a novel rotor structure that applies a consequent-pole structure to an embedded permanent-magnet motor structure, wherein a number of permanent magnets are arranged in a flared structure to constitute a single polarity. In the proposed flared-structured magnet arrangement, it is possible to adjust the angle of the permanent magnet and the polar angle to mitigate the asymmetry of the back-EMF waveform. The proposed structure was optimized with a genetic algorithm and a prototype of the optimal model was constructed and experimentally evaluated to verify its validity. Finally, the performance improvement and validity of the proposed structure were verified by comparing the analysis results of the optimal model with the experimental results.

D-Q Axis Inductance Analytical Calculation for Fractional-Slot Distributed Winding IPM Motor Based on Big-Small Pole Space Method

The d-q axis inductance is the crucial parameter for the interior permanent magnet (IPM) motor. In order to facilitate the design, analysis, and optimization of IPM motors, it is of great significance to develop an accurate and simplified inductance analytical calculation method. Among the existing calculation methods, the magnetic equivalent circuit (MEC) has advantages in the inductance calculation of the IPM motor due to the simple modeling, the fine processing of the saturation region and the visualization of the magnetic field distribution. However, the traditional MEC method is only applicable to the IPM motor with integer-slot distributed winding (ISDW) or fractional-slot concentrated winding (FSCW), while lacking of in-depth research on fractional-slot distributed winding (FSDW). The magnetic circuit topology of FSDW IPM motors is not as single as that of FSCW/ISDW IPM motors. It leads to problems in the traditional MEC method when dividing the d/q axis flux path in FSDW motors. To solve this problem and expand the applications of MEC method, a big-small pole space (BSPS) method is proposed after fully considering the common characteristics of MMF distribution and reluctance distribution in FSDW motors, which fills the gap of MEC method applied to FSDW motors. The BSPS method divides the d-axis flux path according to the asymmetry of the d-axis magnetomotive force (MMF). Based on the divided flux paths, an improved nonlinear MEC model that considers the saturation of stator and rotor is established to calculate d- and q-axis inductances. The results of finite element analysis (FEA) verify the validity of the proposed MEC model with different geometry parameters. Experimental results of an 84-pole/360-slot FSDW I-type IPM wind generator further confirm the validity of the proposed MEC model

Harmonic-Oriented Design and Vibration Characteristic Suppression for Interior Permanent Magnet Motors

In this article, a radial-electromagnetic-force-harmonic-oriented design methodology is proposed to suppress motor vibration. In the proposed methodology, the radial electromagnetic force harmonics innovatively act as the effective bridge between structural field and vibration performance. And avoiding low-order and large-amplitude radial electromagnetic force harmonics is the premise of designing low-vibration PM motors. For extensive investigation, a 36-slot/8-pole IPM motor with different winding configurations and variable rotor parameters is chosen as a design example. Then, vibration suppression methods of lowest-nonzero-spatial-order-shifting in the stator system and dominant-harmonic-amplitude-reduction in the rotor system are proposed. Next, the performances of the IPM motor are simulated for validating the proposed methodology. Finally, a prototype motor is fabricated and experimented. Both theoretical derivation and test results are presented to verify the validity of the motor and the proposed design methodology.

Investigation on sensorless operation of two new fault-tolerant interior permanent magnet motors with trade-off of fault tolerance and flux-intensifying effects

In this paper, two new fault-tolerant interior permanent magnet (FT-IPM) motors are proposed and compared for achieving high fault tolerance and sensorless operating capacity under multiple operations. Most previous studies regarding FT-IPM motors aim to improve fault-tolerant capability but suffer from the saliency characteristic problem, which is unfavorable for sensorless control. To overcome this issue, the design idea of flux-intensifying effect is innovatively proposed. Based on this, two new FT-IPM motors with different rotor structures and slot-pole combinations are developed to achieve flux-intensifying effect. To explore the impact of different motor structures and slot-pole combinations on motor performances, the simulation and experimental results of the two motors are compared and discussed in detail. The comparison results indicate that good fault tolerance and sensorless operating performances need tradeoffs, which provide a reference for balancing the fault tolerance and sensorless operating capacity.

Performance and Short-Circuit Fault Analysis in Hybrid Excited and Interior PM Motors

Performance and Short-Circuit Fault Analysis in Hybrid Excited and Interior PM Motors

Multiple Operation Design and Optimization of a Five-Phase Interior Permanent Magnet Motor Considering Compound Fault Tolerance From Perspective of Flux-Intensifying Effect

Multiple Operation Design and Optimization of a Five-Phase Interior Permanent Magnet Motor Considering Compound Fault Tolerance From Perspective of Flux-Intensifying Effect

Design, Optimization, and Development of an Axial Flux Interior Permanent Magnet Motor with a Novel Flux Barrier

Design, Optimization, and Development of an Axial Flux Interior Permanent Magnet Motor with a Novel Flux Barrier

General Analytical Model and Experimental Verification for Mechanical Stress of High-Speed Interior Permanent Magnet Motors Considering Modified Rotor

General Analytical Model and Experimental Verification for Mechanical Stress of High-Speed Interior Permanent Magnet Motors Considering Modified Rotor

A Methodology for Applying Skew in an Automotive Interior Permanent Magnet Rotor for Robust Electromagnetic and Noise, Vibration and Harshness Performance

Interior permanent magnet (IPM) motors in traction applications often employ discrete rotor skewing constructions to reduce torsional excitations and back-EMF harmonics. Although skewing is very effective in reducing cogging torque, the impact on torque ripple is not well understood and can vary significantly over the operating envelope of a motor. Skewing also leads to the creation of a non-zero axial force that may compromise the bearing life if not considered. This paper introduces a holistic methodology for analyzing the effect of skewing, aiming to minimize torsional excitations, axial forces and back-EMF harmonics whilst mitigating the impact on performance and costs. Firstly, analytical models are employed for calculating cogging torque, torque ripple and axial forces. Then, 2D and 3D finite element analysis are used to incorporate the influence of non-linear material behavior. A detailed structural model of the powertrain is employed to calculate the radiated noise and identify key areas allowing a motor designer to reduce noise, vibration and harshness (NVH). A meticulous selection process for the skewing angle, the number of skew stacks and the orientation of skew stacks is developed, giving particular attention to the effect of the selected pattern on NVH in both forward and reverse rotating directions.

A Multi-Physics Design Approach for Electromagnetic and Stress Performance Improvement in an Interior Permanent Magnet Motor

<div>Electric motors constitute a critical component of an electric vehicle powertrain. An improved motor design can help improve the overall performance of the drivetrain of an electric vehicle making it more compact and power dense. In this article, the electromagnetic torque output of a double V-shaped traction IPMSM is maximized by geometry optimization, while considering overall material cost minimization as the second objective. A robust and flexible parametric model of the IPMSM is developed in ANSYS Maxwell 2D. Various parameters are defined in the rotor and stator geometries to perform an effective multi-objective parametric design optimization. Advanced sensitivity analysis, surrogate modeling, and optimization capabilities of ANSYS optiSlang software are leveraged in the optimization. Furthermore, a demagnetization analysis is performed to evaluate the robustness of the optimized design. At high-speed operation, a rotor core is usually subject to higher deformation due to the high centrifugal force. Thus, rotor stresses are reduced in the optimized design by shaping the flux barriers around the permanent magnets. This enables high structural integrity of the optimized design for high-speed operation along with the improved electromagnetic performance. The multi-physics design approach proposed in this article provides the capability to design and optimize an IPMSM geometry for performance and cost, which are essential objectives to achieve in an electrified powertrain development. Moreover, consideration of rotor stress at high operating speeds extends the applicability of the proposed design approach to high-power, high-speed electric propulsion applications.</div>