Interior Permanent Magnet Motor Research Articles

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

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, 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

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

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>

Research on Five-Phase Flux-Intensifying Permanent Magnet Motor Drive System Based on New Active Sensorless Strategy

For the sensorless control system of the five-phase interior permanent magnet (IPM) motors, its saturation effect greatly affects the estimated accuracy of rotor position, which will not meet the requirement of multi-operating conditions for electric vehicles (EVs). To solve the saturation effect problem, a new active sensorless control strategy is proposed from the perspective of the motor drive system. Based on the analysis of the influence of the saturation effect on the rotor position observation, a five-phase flux-intensifying fault-tolerant interior permanent magnet (FIFT-IPM) motor is proposed with the enhanced reverse saliency effect. Thus, the cross-coupling and parameter variation caused by the saturation effect can be suppressed. Furthermore, from the perspective of the control algorithm, a secondary harmonic suppression method based on adaptive-band filtering (ABF) is proposed to further improve the dynamic and steady-state performance of the five-phase FIFT-IPM motor drive system without position sensor control. Finally, the correctness and effectiveness of the proposed strategy is verified by experimental results.

An improved subdomain method for air gap flux density of interior permanent magnet machines based on rotor reconstruction and flux equivalence

AbstractThe aim of this article is to develop a rotor reconstruction method for the V‐shaped interior permanent magnet (IPM) machine so that the subdomain method to analytically calculate the air‐gap flux density can be applied. With the proposed method, the V‐shaped IPM rotor with rectangular magnets, magnetic barriers, and saturated iron bridges can be transformed into a U‐shaped equivalent analytical model. The geometry and material parameters of the magnets in the equivalent U‐shaped model can be determined according to the flux equivalence in the air‐gap of the motor. Then using the subdomain method on the U‐shaped equivalent rotor, the static magnetic field problem can be solved and the flux density distribution in the air‐gap be obtained. The validity of this method and accuracy of the solution is verified by the finite element method with case studies. Compared with existing methods, the improved subdomain method has higher accuracy in calculating flux density including radial and tangential components. The presented rotor reconstruction method is not only limited to single‐layer V‐shaped rotor, it can also be applied to other IPM rotors with more complex structures. It is valuable in the design, optimisation of IPM motors, and even development of new rotor topology.

Comprehensive Comparative Study on Permanent-Magnet-Assisted Synchronous Reluctance Motors and Other Types of Motor

At present, the induction motor (IM), synchronous reluctance motor (SynRM), ferrite-assisted synchronous reluctance motor (ferrite-assisted SynRM) and interior permanent magnet motor (IPM) are research hotspots, but comprehensive comparative research on the four motors is still rare. This paper mainly compares the four motors from the aspects of electromagnetic performance, material cost and temperature distribution. Firstly, the volume of the four motors is ensured to be the same. The influence of the rotor design parameters of the SynRM, ferrite-assisted SynRM and IPM on the electromagnetic properties of the machine is analyzed. Secondly, based on the effects of each parameter, the overall design parameters of the four motors are determined. The electromagnetic performance, material cost and temperature of the four motors are compared and discussed. Finally, the comparison results are summarized, and the advantages of the four motors are analyzed. In different applications, the electromagnetic performance, heat dissipation and cost requirements of the four motors are different. Therefore, this paper makes a comprehensive comparison of the four motors to provide a reference for the selection of motors for different applications.

Analytical Model for Electromagnetic Performance Prediction of IPM Motors Considering Different Rotor Topologies

Aiming at the problem of long computation time of finite element analysis (FEA) and poor calculation universality of existing analytical models, this paper proposes a general hybrid analytical model to predict the no-load and load performance of interior permanent magnet motors with any slot-pole combination, where the form of magnet can be V-shape, U-shape or flat-shape. The magnets are equivalent correspondingly according to the rotor structure in the modeling process and the motor can be divided into eight types of subdomains, the no-load and load magnetic field of the motors can be obtained by solving the equations established by boundary conditions, where the nonlinear of core is calculated by local MEC. The proposed model can be used to calculate the air-gap magnetic field, no-load back electromotive force, cogging torque and electromagnetic torque of IPM motors with different rotor topologies. The effectiveness of the proposed model is verified by both FEA and experiments. Compared with FEA, this model can consume less time with the acceptable accuracy, which brings convenience to the design and optimization of related types of motors.

Design and Optimization of Interior Permanent Magnet (IPM) Motor for Electric Vehicle Applications

Design and Optimization of Interior Permanent Magnet (IPM) Motor for Electric Vehicle Applications

Design and Finite-Element-Based Optimization for a 12-Slot/10-Pole IPM Motor with Integrated Onboard Battery Charger for Electric Vehicle Applications

Permanent magnet (PM) machines with fractional slot concentrated windings (FSCW) constitute a notably remarkable proposition for electric vehicles. Additionally, an integrated onboard battery charger (IOBC) provides another superiority as it exploits the components of the powertrain to charge the battery without any additional components. Interior permanent magnet (IPM) motor arises as a credible choice due to its high torque density, resulting from the high saliency ratio. The optimal design of an IPM motor has been extensively presented from different perspectives, but the optimal design of a motor employed for IOBC application for both propulsion and charging modes has not been studied extensively. In this paper, the design and optimization of a 12-slot/10-pole IPM motor with IOBC are studied under both propulsion and charging modes. A finite-element-based optimization with the aid of a genetic algorithm technique is proposed to obtain the optimal machine by maximizing the average torque and minimizing the torque ripple, core losses, and magnet size.