Interior Permanent Magnet Motor Research Articles

Analysis of Interior Permanent Magnet Motor for Mechanical Safety

Analysis of Interior Permanent Magnet Motor for Mechanical Safety

Design and Comparison of Interior Permanent Magnet Motor Topologies for Traction Applications

Traction motors play a critical role in electrified vehicles, including electric, hybrid electric, and plug-in hybrid electric vehicles. With high efficiency and power density, interior permanent magnet (IPM) synchronous machines have been employed in many commercialized electrified powertrains. In this paper, three different IPM rotor design configurations, which have been used in electrified powertrains from Toyota, Nissan, and General Motors, are comparatively investigated. Each topology is redesigned and improved to meet new design requirements based on the same constraints. The designed motors are then compared and comprehensively evaluated for motor performance, torque segregation, demagnetization, mechanical stress, and radial forces. The results suggest that the single V-shaped configuration achieves the best overall performance and is thus recommended as the best candidate.

An inverse problem methodology for design and optimization of an interior permanent magnetic BLDC motor

In the theory of inverse problem, the parameters identification by optimization is considered as one of its main applications. This paper presents an optimal design of a slotted permanent magnet Brushless DC (BLDC) motor with surface mounted magnets. The inverse problem method is applied by using a thriving solver afforded by the nonlinear optimization toolbox of Matlab ‘Fmincon’, this function is based on Active-Set and Sequential Quadratic Programming approaches with calculation of the Hessian from Quasi-Newton algorithm. The optimal magnetic field density considered as the main objective is obtained by picking several parameters and analyzing their effects. The proposed approach is highlighted by using the obtained parameters in the design of the motor. The Finite element method is applied on the motor for numerical analysis by using FEMM magnetic coupled with Matlab code. Effectiveness and robustness of the proposed approach are verified by a comparison between the initial and optimized design.

Performance Evaluation of Interior Permanent Magnet Motors Using Thin Electrical Steels

This work investigates the impact of thin electrical steel laminations on the performance of interior permanent magnet (IPM) motors for electric vehicle tractions. Three different electrical steel grades are used in IPM motor designs and the performance is evaluated by simulation. It is found that thin laminations can improve the efficiency of the IPM motor, but the output torque could be slightly reduced due to low saturation flux density. Therefore, direct replacement of core materials for the same motor design may not be suitable. This paper presents the considerations for the design of IPM motors using thin laminations. The motor performance, including torque, efficiency, and constant power speed range is evaluated. A process is developed for the design of high performance IPM motors using thin laminations. Experimental studies are conducted to validate the simulations and designs.

Stator Winding Interturn Short-Circuit Faults Severity Detection Controlled by OW-SVPWM Without CMV of a Five-Phase FTFSCW-IPM

This paper proposed a method to detect different interturn short-circuit fault severity by analyzing zero-sequence current for a new five-phase fault-tolerant fractional-slot concentrated winding interior permanent magnet motor (FTFSCW-IPM). To eliminate the effect of common-mode voltage in single dc power supply application, fault severity analysis is conducted based on an open-end winding (OW) space vector. This new method is verified by simulation and experimental results in a five-phase FTFSCW-IPM OW system.

Characteristics of new interior permanent magnet motor using flared-shape arrangement of ferrite magnets

Characteristics of new interior permanent magnet motor using flared-shape arrangement of ferrite magnets

Effect of Compressive Stress on Iron Loss of Gradient Si Steel Sheet

SUMMARYA gradient Si steel sheet, which has high Si content in the surface layer and low Si content in the center of the thickness, shows extremely low iron loss in the high‐frequency range. In this paper, the magnetic properties of gradient Si steel sheets under compressive stress were investigated. In a 3.5% Si steel sheet, the iron loss under compressive stress increases with increase in compressive stress. On the other hand, a gradient Si steel sheet shows extremely low iron loss under compressive stress. This decrease is due to the residual tensile stress in the surface layer of the gradient Si steel sheet. To evaluate the effect of core materials on the iron loss of the motor, we fabricated interior permanent magnet motors using 3% Si steel, 6.5% Si steel, and gradient Si steel sheets. In the motor using a 3% Si steel sheet, the motor loss increases after the heat shrinking. On the other hand, in the motors using 6.5% Si steel and gradient Si steel sheets, the motor loss shows little change after the heat shrinking.

Performance Analysis of Interior Permanent Magnet Motor Using Overlapping Windings With Fractional Ratio of Slot to Pole Pair

Conventional concentrated windings with fractional-slot per-pole per-phase (SPP) are widely used to reduce the cogging torque and ripple torque of interior permanent magnet (IPM) machines. However, the rich magnetic motive force (MMF) harmonics of the fractional SPP concentrated winding (FSCW) will result in high rotor losses. This paper proposes a new overlapping winding with fractional slot per-pole-pair (SP), which can greatly reduce the pulsating torque with lower winding harmonics. First, the principle of the proposed winding configuration is analyzed with respect to the cogging effect and the stator MMF. Then, the electromagnetic performances of the new fractional SP windings are compared to that of integer SPP windings, FSCWs and odd SP windings in terms of airgap flux density, back electromotive force, cogging torque, average torque, torque ripple, and losses. It is found that the IPM machine with the proposed winding configuration has the lowest cogging torque and ripple torque, and its winding MMF harmonics are significantly smaller than that of the IPM machine with FSCWs.

Unified Calculation Method for Motor Torque in Reluctance Network Analysis

SUMMARYA reluctance network analysis (RNA), which is an improved magnetic circuit method, has some advantages: the analytical model is simple, the calculation accuracy is relatively high, and a coupled analysis with an electric circuit, a heat circuit, a motion equation, and so on, is fundamentally easy. The RNA has been applied to the dynamic analysis of several motors such as a surface permanent magnet (SPM) motor, an interior permanent magnet (IPM) motor, and a switched reluctance (SR) motor. The dynamic characteristics of these motors including starting and a sudden load change can be calculated by an RNA. However, the torque calculation methods for these motors are different from each other. This paper presents a unified calculation method for the motor torque in an RNA, which does not depend on the types and structures of motors. The validity and availability of the proposed method are demonstrated by a finite element method (FEM) and an experiment.

Large-Scale Design Optimization of PM Machines Over a Target Operating Cycle

A large-scale finite element model-based design optimization algorithm is developed for improving the drive-cycle efficiency of permanent magnet (PM) synchronous machines with wide operating ranges such as those used in traction propulsion motors. The load operating cycle is efficiently modeled by using a systematic k -means clustering method to identify the operating points representing the high-energy-throughput zones in the torque–speed plane. The machine performance is evaluated over these cyclic representative points using a recently introduced computationally efficient finite element analysis, which is upgraded to include both constant torque and field-weakening operations in the evaluation of the machine performance metrics. In contrast with the common practice, which aims at enhancing the rated performance, the entire range of operation is considered in the present design optimization method. Practical operational constraints imposed by the voltage and current limits of the motor-drive system, excessive PM demagnetization, and torque ripple are accounted for during the optimization process. The convergence to the optimal design solutions is expedited by utilizing a new stochastic optimizer. The developed design algorithm is applicable to any configuration of sinewave-drive PM and synchronous reluctance motors over any conceivable load profile. Its effectiveness is demonstrated by optimizing the well-established benchmark design represented by the Toyota Prius Gen. 2 interior PM motor configuration over a compound operating cycle consisting of common U.S. driving schedules. Multiphysics electromagnetic, thermal, and mechanical performance of the optimized design solutions is discussed in a postdesign optimization stage.

Analytical Calculation of D- and Q-axis Inductance for Interior Permanent Magnet Motors Based on Winding Function Theory

Interior permanent magnet (IPM) motors are widely used in electric vehicles (EVs), benefiting from the excellent advantages of a more rational use of energy. For further improvement of energy utilization, this paper presents an analytical method of d- and q-axis inductance calculation for IPM motors with V-shaped rotor in no-load condition. A lumped parameter magnetic circuit model (LPMCM) is adopted to investigate the saturation and nonlinearity of the bridge. Taking into account the influence of magnetic field distribution on inductance, the winding function theory (WFT) is employed to accurately calculate the armature reaction airgap magnetic field and d- and q-axis inductances. The validity of the analytical technique is verified by the finite element method (FEM).

Equivalent Circuit Modeling of a Hysteresis Interior Permanent Magnet Motor for Electric Submersible Pumps

This paper presents the magnetic and electrical equivalent circuits of a hysteresis interior permanent magnet (IPM) motor. A hysteresis IPM motor is a solid rotor hybrid synchronous motor combining hysteresis phenomena and permanent excitation in the rotor. When installed in thousands of feet under the sea to drive an electric submersible pump (ESP), it can self-start the ESP without the need of any position sensors, and can improve the efficiency, the performance, and the reliability of the ESP. In this paper, equivalent circuit models are used to predict the transient run-up responses of a 2.5 kW prototype hysteresis IPM motor. Analysis results are compared with 2-D finite-element analysis (FEA) results as well as experimental results. There exists a reasonably close agreement between analytical, FEA, and experimental results, which validates the accuracy of the equivalent circuit models of a hysteresis IPM motor.

Optimal Design of a New Interior Permanent Magnet Motor Using a Flared-Shape Arrangement of Ferrite Magnets

This paper proposes the optimal design of a new interior permanent magnet (IPM)-type brushless dc (BLdc) motor using low-price ferrite magnets. The new IPM motor has the structure of C-type ferrite magnets featuring a flared shape to obtain high motor performance. To maximize the flux density and minimize the torque ripple, the flared-shape rotor structure is optimized by algorithms, such as the Kriging method based on Latin hypercube sampling and a genetic algorithm. The analyses of basic and optimal designs utilize a 3-D finite-element method, and then, the validity of the optimal design is verified through fabrication of actual prototypes.

Electromagnetic Performance Analysis and Verification of a New Flux-Intensifying Permanent Magnet Brushless Motor With Two-Layer Segmented Permanent Magnets

Permanent magnet brushless (PMBL) motors have been widely applied in electric vehicles, since they inherently offer high efficiency, high power density, and free maintenance. However, because of the existing problem of uncontrollable flux, their constant-power speed range is relatively narrow. In order to gain a wide speed range, by employing the new concept of the flux-intensifying effect, a new flux-intensifying PMBL (FI-PMBL) motor is proposed in this paper. The proposed motor is innovatively designed, where the topology of two-layer segmented PMs and non-uniform air gap are adopted to make the corresponding $d$ -axis inductance $L_{d}$ become greater than the $q$ -axis inductance $L_{q}$ , which is far different from the conventional interior PM motor. By using the finite-element methods, the electromagnetic performances of the proposed motor are evaluated in detail. Simulation results show that the proposed motor possesses preferable flux-weakening capability and wide speed range. In addition, the experimental results of the FI-PMBL prototype are given to verify the performances of the motor.

Analytical Investigation Into Magnet Eddy Current Losses in Interior Permanent Magnet Motor Using Modified Winding Function Theory Accounting for Pulsewidth Modulation Harmonics

The study of the interaction between an interior permanent magnet (IPM) motor and a pulsewidth modulated (PWM) converter is increasingly becoming important, especially in the case of high-speed drives owing to the losses caused by modulation. Considering the significance of machine–converter interaction, this paper proposes a novel method to calculate magnet eddy current losses in an IPM used in traction applications by incorporating both PWM harmonics as well as rotor geometry and design parameters. The voltage harmonics from the PWM are incorporated into a series of steps in order to calculate the stator magnetomotive force (MMF) using the modified winding function theory. The rotor MMF and, subsequently, the magnet losses are computed using a magnetic circuit model incorporating the harmonics from the stator MMF as well as the flux barrier and the rotor geometry. The results have been demonstrated analytically for various cases of modulation and PWM input parameters to study the dependence of magnet losses on converter properties. The analytical results have been validated by finite-element analysis and experimental investigations.

Design and Analysis of Low-Cost Tubular Fault-Tolerant Interior Permanent-Magnet Motor

Tubular motors are suitable for active vehicle suspension due to their zero net radial force and volumetrically efficient. This paper proposes a new low-cost tubular fault-tolerant (TFT) interior permanent-magnet (IPM) motor for the high reliability operation of the active vehicle suspension system. The key is that the proposed motor incorporates the concept of fault-tolerant teeth to provide the desired decoupling among phases and adopts the ferrite magnet material to reduce the usage of rare-earth PMs. Its electromagnetic performances are investigated, such as flux linkage, back electromotive force, mutual- and self-inductances, and detent and thrust forces. A finite-element method is employed to verify the theoretical analysis, showing that the proposed TFT PM motor not only has the merits of low-cost, strong mechanical integrity, but also offers good fault-tolerant ability and high thrust force capability.

A New Coreless Axial Flux Interior Permanent Magnet Synchronous Motor With Sinusoidal Rotor Segments

Axial flux permanent magnet (AFPM) motors are frequently used in many applications. Axial gap coreless motors with surface-mounted magnets are the most noteworthy ones due to their potentially higher efficiency and smaller axial length. In this paper, a new spoke-type AFPM coreless disk motor with dual rotor and single stator is proposed with sinusoidal rotor segments. This new disk-type motor is an interior PM (IPM) motor with spoke-type rotor and variable air gap to obtain sinusoidal back Electro-Motive Force waveform. It is shown that it is possible to increase the air-gap flux density in the proposed new coreless AF-IPM motor and increase the torque output compared with the conventional surface-mounted AFPM motors.

An Improved Method for Armature-Reaction Magnetic Field Calculation of Interior Permanent Magnet Motors

This paper proposes an improved analytical method to calculate the armature-reaction magnetic field (ARMF) of interior permanent magnet motors. Based on the winding function, the armature-reaction magnetic motive force is divided into the q-axis component and the q-axis component to facilitate the analysis. Considering the flux paths, the difference of rotor magnetic potentials in the d-axis and the q-axis is illustrated, which improves the accuracy of the ARMF calculation. The validity of the analytical technique is verified by the 2-D finite-element analysis.

Shape design optimization of interior permanent magnet motor for vibration mitigation using level set method

This paper presents a new optimization method to obtain the structural design of permanent magnet motor which can reduce the mechanical vibration. The optimization problem is formulated to minimize a multi-objective function including the mean compliance of the whole stator for maximizing the stiffness under the magnetic force and the torque ripple by aligning torque profiles to a constant target value for maximizing the magnetic performance, with constraint for material usage. The level set function is introduced for representing the structural boundaries and calculating the material properties. A coupled magneto-mechanical analysis is performed to verify the vibration characteristic of the motor system and obtain the design sensitivities. To confirm the usefulness of the proposed design method and to obtain the optimum structural design for low vibration motor, a design example of 20 kW interior permanent magnet motor developed for the power train of a hybrid electric vehicle is provided.

Comparative Study of Surface-Mounted and Interior Permanent-Magnet Motors for High-Speed Applications

This paper investigates the surface-mounted permanent-magnet (SPM) and the interior permanent-magnet (IPM) motors for high-speed applications. An SPM motor and an IPM motor are designed with the same power/speed rate and the same key dimensions. Finite-element analysis is used to compare the mechanical, electromagnetic, and antidemagnetization performances of the two motors, and lumped parameter thermal networks are involved to compare their thermal performances. It can be concluded from the comparisons that the IPM motor has comparable electromagnetic performances with the SPM motor in high-speed operations, and its costs and torque per PM weight are superior to those of the SPM motor. However, its rotor structure is not as robust and is prone to irreversible demagnetization.