Search

In order to improve the torque density of the magnetic flux concentrated permanent magnet synchronous motor utilizing a ferrite permanent magnet, it is important to reduce the leakage magnetic flux flowing through the rotor core. For satisfying the robustness of the rotating body and improving the torque density, we propose a structure in which two types of cores with different shapes are cross laminated. The proposed rotor structure consists of a core with a bridge that is necessary to maintain the rigidity of the rotor assembly, and a rotor assembly by cross laminating the segment-type rotor cores necessary for minimizing the leakage flux as well as improving the torque density. The complex three-dimensional (3-D) magnetic circuit of the cross-laminated rotor assembly has been modeled as a two-dimensional (2-D) model on the mathematical basis of an equivalent magnetic circuit. Using the equivalent 2-D model, the design of the cross-laminated rotor shape and the electromagnetic characteristics were examined comprehensively. At the same time, mechanical stresses due to centrifugal force and torque transmission between rotor core and shaft were examined. Finally, after the prototype was fabricated, the analysis and design methods were verified through no-load and load tests. [ABSTRACT FROM AUTHOR]

In this paper, the design of the concentrated flux-type synchronous motor (CFSM) using ferrite permanent magnets to improve torque is proposed for an automotive chassis actuator. The thin pancake type CFSM of this paper has considerable axial magnetic leakage flux due to structural reasons. It is, therefore, necessary to improve the torque. In order to meet the required specifications in a constrained installation space, this paper proposes two methods for torque improvement. The first method is the alternate-stacking core as this structure removes the magnetic leakage flux path. The second method is the rotor overhang that increases the air-gap flux density. Furthermore, the structures require a three-dimensional (3-D) finite element method (FEM) analysis for accuracy. However, to analyze the characteristics easily and quickly, the 3-D structure is made into the equivalent 2-D FEM through an analytical method using an equivalent magnetic circuit. Finally, in this paper, the validity of the design process and the effectiveness for torque improvement is verified through experiments. [ABSTRACT FROM AUTHOR]

In order to improve the performance of the wound field synchronous motor (WFSM), the permanent magnet assist (PM-assist) is investigated in this paper. The effect of the PM-assist is dependent on the inserted position of the PMs. Thus, four models whose PMs are inserted at each different position are suggested. Then, the most effective position of the PM is decided by the mean torque per employed amount of the PM. By inserting the PMs into the decided position of a WFSM designed for a small electric vehicle traction, the PM-assisted WFSM is designed. By comparing the torque and the efficiency of the original WFSM and the PM-assisted WFSM, the effectiveness of the PM-assist is figured out. Finally, the validity of this research is verified by the experiment using the manufactured WFSM. [ABSTRACT FROM AUTHOR]

In rotating motors, an electromagnetic analysis using finite-element analysis is performed according to the time interval such as the steps of the rotation angle. If the uncertainty of time variable is necessary to be handled, the time interval should become smaller than uncertainty values. It causes an increase of the cost even if the surrogate model is applied. Thus, space-time kriging surrogate model is proposed to consider time variable as well as space variable in the design stage. The proposed model handles time variable and predicts responses between time intervals to obtain outputs for the tiny uncertainty of time variable. The performance of prediction is verified with simulation data and then the reliability estimated by the proposed model is compared with measured data from manufactured prototypes. [ABSTRACT FROM AUTHOR]

This paper proposes a new numerical formula and a design method to reduce the torque ripple while improving efficiency and the control performance of an interior permanent magnet synchronous motor. In previous studies, the inverse cosine function (ICF) has been used for torque ripple reduction by making the air gap flux density distribution sinusoidal under a no-load condition. However, in this paper, the advanced inverse cosine function (AICF) based on the ICF is proposed. It determines an asymmetric rotor shape for rendering the air gap flux density distribution sinusoidal, considering a certain load condition. In addition to the torque ripple reduction, lower peak values, the total harmonic distortion (THD) of the induced voltage, and a lower iron loss can be achieved by applying the AICF, compared to the other conventional methods. The lower peak value and THD of the induced voltage are important because they affect the control performance of the motor. The lower iron loss can also lead to a higher efficiency, particularly, in the high-speed region. To verify the validity of the proposed design method, the characteristics of 8-pole, 12-slot motors that have different rotor shapes are analyzed using finite element analysis and experiments. [ABSTRACT FROM AUTHOR]

Permanent magnet (PM) assisted claw-pole synchronous motor (CPSM) has commonly been used in a variety of industrial applications thanks to its robust structure and high energy density. However, such a motor has an axially asymmetric rotor configuration, which induces the corresponding 3-D magnetic field distribution. Thus, this paper proposes an infinitesimal hexahedron-element-based 3-D equivalent magnetic circuit network (EMCN) method in order to estimate the performance of the PM-assisted CPSM. The hexahedron element is considered an optimum unit element in describing the configuration of the PM-assisted CPSM in detail. That eventually makes it possible to evaluate the specific 3-D magnetic field distribution from which the flux linkage, the back-electromotive force, and the torque are also being calculated. The 3-D EMCN results are compared with 3-D finite element analysis (FEA) data and/or experimental data to validate their accuracy. Finally, it is proved that the scalar-potential-based 3-D EMCN method requires less computing time than the vector-potential-based 3-D FEA. [ABSTRACT FROM AUTHOR]

Today, performance improvements such as reducing the time response and enhancing the efficiency of the electrical motor are one of the most important challenges. In the design of a permanent-magnet (PM) motor, the variables for sizing include the shape ratio (SR), the torque per rotor volume (TRV), and the torque density (TD), and these variables are important for determining the mechanical and electrical characteristics of the motor. This study investigated the changing patterns of the motor parameters (back electromotive force, inductance, resistance, etc.) and the motor characteristics with the changes in the SR, TRV, and TD with respect to the PM synchronous motor, and sought to determine the SR and TRV values. Toward these ends, this study proceeded with the initial design of the spoke-type (flux-concentrated) PM motor. Then, the motor parameters of the initial model were calculated using finite-element analysis. Based on the motor parameters of the initial model, the changing patterns of the electrical and mechanical characteristics of the motor according to the changes in the SR, TRV, and TD were investigated. In addition, the SR, TRV, or split ratio that can enhance the mechanical characteristics and efficiency of the motor were determined and reflected in the design. [ABSTRACT FROM PUBLISHER]

High-temperature superconductor (HTS) technology has been studied recently for the use with superconducting high-power transmission and distribution, motors, generators, and fault-current-limiting devices such as cables and transformers. HTS technology, which can provide a large electromotive force in a small area owing to its large current density compared to that of a normal conductor, can reduce the weight and loss of a generator when compared to the attributes of a conventional machine. Moreover, once the HTS conductor has stabilized, the challenge of cooling the windings in large-scale generators can be resolved. Therefore, the technology has been studied for application with 10-MW-class superconductor wind-turbine generators. Although an HTS conductor generator offering a higher torque density, lower weight, and higher efficiency than a conventional generator can be designed, the design must satisfy the requirements of the critical magnetic field, critical current, and critical temperature of the superconducting winding. The HTS homopolar superconducting synchronous generators have a simple structure with a fixed HTS conductor and are one of the most suitable types of generator that is able to satisfy these requirements more easily. In this paper, we propose a 10-MW homopolar-type wind-turbine generator. [ABSTRACT FROM PUBLISHER]

The reduction of cogging torque is the most important design objective for electric power steering (EPS) motors, because the rotation characteristics of the motor are directly transmitted to a driver. Therefore, a variety of optimal design methods are applied to reduce the cogging torque for EPS motors. However, the measured cogging torques of fabricated models are significantly greater than the finite‐element analysis (FEA) results, because the additional harmonic components (AHCs) of the cogging torque are generated by manufacturing tolerances. The cogging torque generated by manufacturing tolerances can be divided into two components, which are generated by stator and rotor tolerances. In this study, AHCs, which cause cogging torque, are analysed by FEA by applying various tolerances to the analysis model, and harmonic analysis is also conducted. The relation of AHC generated from the stator and rotor is analysed by a rotor swapping test. Consequently, this study can be helpful to analyse the components of the cogging torque generated by manufacturing processes. [ABSTRACT FROM AUTHOR]

Recently, studies on the hybrid excitation synchronous motor using permanent magnet (PM) together with field windings have been actively conducted. In this regard, this paper seeks to investigate brushless hybrid excitation synchronous motors with improved rotors. The design was performed using an equivalent magnetic circuit to determine the best of four possible different structures. Using a finite-element analysis (FEA), the back electromotive force (EMF) per PM usage and the phase back EMF of each type were calculated and compared, and the design that can best reduce costs and increase torque density was determined. A detailed design of one of the four structures with excellent characteristics was performed, and the associated characteristics and problems were verified. An improved rotor structure was proposed to resolve the identified problems and improve performance. The phase back EMF and the total harmonic distortion of the phase back EMF, cogging torque, load torque, and torque ripple of the improved rotor structure were verified through the application of the FEA. In addition, the prototype motor was fabricated, and a no-load test was conducted to compare the test results and analysis results on the phase back EMF. The reliability of the analysis results was confirmed by comparison between test results and analysis results on the input current, line to line voltage, and efficiency under the same output conditions through the load test. [ABSTRACT FROM AUTHOR]

This paper deals with the post-assembly magnetization process of motors using ferrite permanent magnets (PMs). In order to meet the needs of mass production, most motors are magnetized post assembly. However, increasing complex shapes are required to maximize the flux of PMs. As a result, certain locations in the magnet are not fully magnetized by the magnetizing fixture due to insufficient magnetomotive force. Therefore, an analysis concerning the post-assembly magnetization is needed. In this paper, the concentrated flux spoke-type synchronous motor is analyzed with regard to the magnetization process. Owing to more flux, this motor is designed as a V-shape PM. Therefore, it is not fully magnetized according to magnet shape. By identifying the effect of the magnet shape, the magnetization level is compared by the amount of flux linkage between post assembly and at full magnetization. Finally, the back electromotive force is estimated by the post-assembly magnetization method according to the magnet shape. [ABSTRACT FROM AUTHOR]

As materials with various properties have been developed for the improvement of performance and lowering the material cost of permanent magnet (PM) motors, the properties of the materials have become major factors in determining the motor performance. As such a material, the recently developed anisotropic bonded NdFeB PM showed a nonlinear demagnetization curve. Thus, in this paper, by considering the nonlinear property of the PM, a process to calculate the operating point, coupled with a nonlinear analysis of the core, is proposed, and by applying this process, the characteristics of interior PM synchronous motor according to different rotor designs are investigated. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of the geometry design parameters of an interior permanent magnet synchronous motor with concentrated winding on the saliency-based sensorless drive feasibility. To evaluate the sensorless controllability of the motors, two different methods to estimate the rotor position error are proposed. By using the methods, the geometry design parameters in the stator are analyzed to figure out which ones have a positive effect on the sensorless drive. The analysis results show that the configuration of the tooth tip is one of the major factors in reducing the estimation error. Based on the results, an optimum design parameter is selected considering both the drive feasibility and the back electromotive force. Last, a final model is proposed and manufactured for electric vehicle traction. The validity of the proposed estimation methods and the design result are verified by the experiments. [ABSTRACT FROM AUTHOR]

This paper proposes the design process of a 2.62-kW 150-krpm high-speed surface-mounted permanent-magnet synchronous motor. To meet the required specifications, the numbers of poles and slots were determined by considering the maximum speed and the rotary stability affected by the vibration of the rotor. In addition, this paper describes not only the appropriate material selection method but also the appropriate geometry design method based on analytic approaches. Furthermore, to precisely evaluate the bearing and windage losses at a high speed, a method that combines the finite-element method and the experiment results of the prototype was used. As a result, an improved motor was designed, which had higher maximum power and speed than the prototype and a lower mass moment of inertia. Finally, tests were conducted to verify the validity of the proposed design process and the effectiveness of the motor. [ABSTRACT FROM PUBLISHER]

Motors for dual-clutch transmission (DCT) system are required to minimize its size because of limited space on transmission. Characteristics, low cost, and high productivity are essential to DCT motor for competitiveness of mass production. Hence, concentrated flux-type ferrite magnet motor is suggested to meet the needs of DCT motor. Because concentrated flux-type permanent magnet motor has a high torque density, it is possible for ferrite magnet motor to achieve air-gap flux as high as a rare-earth magnet motor. The most important thing for the design of concentrated flux-type motor is to reduce the flux leakage. Increase in magnetic reluctance of flux leakage path is necessary to reduce the flux leakage. Accordingly, segmented rotor core is required for the size reduction of motor. In the case of segmented rotor core type, it is necessary to have complex mechanical structure to maintain circular rotor shape and fix to shaft. Since those additional structures seriously deteriorate productivity, plastic injection molding type rotor is suggested in this paper to solve the problem. [ABSTRACT FROM AUTHOR]

The magnetic properties of a motor core deteriorate during the manufacturing process due to mechanical stresses in the materials. It is particularly hard to predict the characteristics of the slinky-laminated electrical machines, because stresses and strains occur simultaneously in the core. To examine the B – H curve and the iron loss of a core affected by the manufacturing process, a slinky-laminated surface-mounted permanent magnet synchronous motor (SPMSM) was proposed as an analysis model. The magnetic properties of the slinky-laminated core and the stacked core were compared as the results of material experiments, using the proposed motor core. With the examined material data, the iron loss of the slinky-laminated SPMSM was investigated via the finite-element method (FEM). Finally, the proposed motor was subjected to a no-load test and a mechanical loss test. Based on the test results, the actual iron loss of the motor was obtained through loss segregation and was then compared with the FEM results to verify the validity of the material experiment and loss analysis methods. [ABSTRACT FROM AUTHOR]

This paper proposes a new design technique for improving torque performance of interior permanent magnet (IPM) motors with consideration of the thermal characteristic of magnet. To verify the driving performance of IPM motor at operating temperature, a magnetic-thermal coupled analysis was performed with a heat source, such as iron loss and copper loss, and the thermal characteristics of permanent magnet (PM) is considered to define the magnetic property. The optimization problem is formulated to minimize the harmonics of magnetic flux, which cause iron loss, as well as to maximize the output torque for satisfying the design target. To obtain an optimal rotor shape of the IPM motor, which is composed of both PM and ferromagnetic material, a multi-phase level set model is employed for representing the precise boundaries of the magnetic materials. A design example of a motor with Nd–Fe–B magnet, which has a tendency to be demagnetized at high temperature, is provided to verify the effectiveness of the proposed method. [ABSTRACT FROM PUBLISHER]

This study investigates the influence of the stator configuration of low‐speed sensorless‐controlled interior permanent magnet synchronous motors (IPMSMs) with concentrated winding on the sensorless drive feasibility and iron loss. To evaluate the sensorless controllability of the motors, a mathematical and simulation process of estimating the rotor position error is proposed. In addition, the harmonic iron loss under a load condition is analysed via two‐dimensional non‐linear finite element analysis. Considering both the sensorless drive feasibility and iron loss, the four different IPMSMs, which have different tooth tip configurations in the stator, are examined. It is shown that the machine with a relatively short and thin stator tooth tip has better sensorless drive controllability and lower harmonic iron loss than the others. Based on the analysis result, a final model applied with stator chamfer for electric vehicle traction is proposed and manufactured. The validity of the simulations and the design method are verified by the experiments. [ABSTRACT FROM AUTHOR]

Consideration of the saturation in the core is essential in designing motors for automotive application, because of the stringent size limitations in automotive electric motors, such as those equipped with electrical power steering. In the design of squirrel-cage induction motors, equivalent circuit analysis using lumped parameters is often used to investigate the motor performance. However, estimation of the motor characteristics has been limited because the standard equivalent circuit that considers space harmonics does not consider the core loss. To improve the reliability of the characteristic analysis, a new method that can solve these problems is required. Thus, study of a new equivalent circuit that considers the saturation in the core and the core loss harmonics is needed. Therefore, to obtain the reliable characteristics of induction motors, this paper presents a modified space harmonic equivalent circuit that considers the harmonics of core loss resistance. The modified equivalent circuit is verified by comparing the analysis results of the suggested method and the experimental results of the test model. [ABSTRACT FROM AUTHOR]

Interior permanent magnet synchronous motors (IPMs) usually use NdFeB for achieving high-torque and high-efficiency performance. This paper reviews the performance of concentrated-flux-type ferrite magnet motors (CFFMs) that use ferrite, as an alternative to the general type of IPMs that use NdFeB. A structure to reduce the motor volume and improve the torque density of CFFMs is suggested in this paper. The characteristics of CFFMs for different rotor types are analyzed. The motor parameters are analyzed. Using 2-D finite element analysis (FEA), the efficiency and size of the CFFMs are compared with each other. This paper discusses the results of stress analysis for each rotor type using 2-D FEA. Finally, it suggests a CFFM structure to replace the general type of IPMs that use NdFeB. The proposed LC-type has the highest torque density among all the ferrite rotor types. It is seen that the proposed LC-type ferrite-model replacement for the Nd model is the best choice of all the types. [ABSTRACT FROM AUTHOR]

Induction motors are widely used in various industrial applications with different torque-speed characteristics. Since the configuration of the rotor slot has a great impact on the electromagnetic torque-speed characteristics, a design optimization process is necessary to improve the motor performance of the induction motor. The material boundaries of the rotor slot are represented by a level set function, and a voltage driven time-harmonic field analysis is performed to estimate the characteristics of the induction motor. An optimization problem is formulated to maximize the torque at one speed either a rated or starting condition constrained by the torque at other speeds, starting currents and efficiency. A level set equation with an augmented Lagrangian method is derived to find the optimal design. Optimal results are achieved by updating the sequential changes of the material region driven by the shape derivative. The design flexibility of the proposed method is confirmed to obtain National Electrical Manufacturers Association (NEMA) designs satisfying different torque characteristics. [ABSTRACT FROM AUTHOR]

This paper deals with the temperature estimation of interior permanent magnet synchronous motor (IPMSM). A thermal equivalent circuit of IPMSM is proposed with considering eddy current loss of PM as well as core losses of rotor. Heat sources, which are core loss of stator/rotor core and eddy current loss of PM, are calculated by numerical method to enhance the accuracy of thermal estimation. The thermal equivalent model is represented by the thermal resistances and thermal capacitances, which are determined by motor configuration. Meanwhile, a temperature test is performed using prototype to determine the heat transfer. Finally, this thermal equivalent model is verified by a temperature test in a 25 kW 12-pole/18-slot IPMSM. [ABSTRACT FROM PUBLISHER]

This paper proposes a new optimization method to design the rotor of interior permanent magnet (IPM) motor which consists of a permanent magnet (PM) and ferromagnetic material (FM) for reducing the torque ripple. To express three different material properties (PM, FM, and air), a multi-phase level-set model representing two level-set functions is introduced and the concept of a phase-field model is incorporated to distribute level-set functions for controlling the complexity of the structural boundaries. The optimization problem is formulated to minimize the torque ripple under the volume constraints of each material. Two level-set functions are updated with their respective design sensitivities. To verify the usefulness of the proposed method, the rotor design example of the IPM motor is performed and a novel configuration is obtained. [ABSTRACT FROM PUBLISHER]

In this paper, the bridge shape of interior permanent magnet synchronous motor (IPMSM) is designed for integrated starter and generator (ISG) which is applied in hybrid electric vehicle (HEV). Mechanical stress of rotor core which is caused by centrifugal force is the main issue when IPMSM is operated at high speed. The bridge is thin area in rotor core where is mechanically weak point and the shape of bridge significantly affects leakage flux and electromagnetic performance. Therefore, bridge should be designed considering both mechanic and electromagnetic characteristics. In the design process, we firstly find a shape of bridge has low leakage flux and mechanical stress. Next, the calculation of mechanical stress and the electromagnetic characteristics are performed by finite element analysis (FEA). The mechanical stress in rotor core is not maximized in steady high speed but dynamical high momentum. Therefore, transient FEA is necessary to consider the dynamic speed changing in real speed profile for durability experiment. Before the verification test, fatigue characteristic is investigated by using S–N curve of rotor core material. Lastly, the burst test of rotor is performed and the deformation of rotor core is compared between prototype and designed model to verify the design method. [ABSTRACT FROM PUBLISHER]

On account of high efficiency and high power density, permanent-magnet synchronous motors (PMSMs) are mainly applied to a high-speed machine. Especially, because of relatively easy magnetic circuit design and control, a surface-mounted PMSM of them is adopted in almost the entire high-speed applications. However, the surface-mounted PMSM has some weak points due to a sleeve, which is nonmagnetic steel used in order to maintain the mechanical integrity of a rotor assembly in high-speed rotation. The sleeve causes additional eddy current loss in the rotor besides permanent magnet and increases not only magnetic air-gap length but manufacturing costs by raw material purchase and shrink fitting. Thus, in this paper, a new rotor shape for a high-speed interior permanent-magnet synchronous motor (IPMSM) is presented in order to resolve the faults of the surface-mounted PMSM. Moreover, the amount of permanent magnet employed in the IPMSM is decreased by approximately 53% than that of the surface-mounted PMSM. Except for the rotor configuration, all design conditions of the IPMSM are identical compared with the surface-mounted PMSM. Finally, the IPMSM is fabricated, and its superiority and reliability in high-speed operation are verified by test. [ABSTRACT FROM PUBLISHER]

Radial force and tangential force, which deform stator core, are the main causes of vibration and noise. There are many methods to minimize such electro-magnetic exciting forces by designing of magnetic core shape. However, modification of rotor shape increases development cost of the motor. Therefore, step skewed rotor is applied to the design to reduce electro-magnetic exciting force so that both reduction of vibration and noise and cost-effectiveness of development can be achieved. In order to consider step skewed rotor in interior permanent magnet synchronous motor (IPMSM), 3-dimensional finite element analysis (FEA) is used to consider leakage flux in axial direction and overhang effect. Furthermore, deformation of stator core caused by exciting force is analyzed to explain the mechanism of reduction of vibration and noise by skewed rotor. Comparison between prototype and step skewed model is performed in terms of analysis of exciting force, deformation of stator and experimental result of vibration to verify the analysis method. [ABSTRACT FROM AUTHOR]

This paper deals with two types of interior permanent magnet (IPM) motors, S-type and V-type. The V-type is optimized in the rotor shape to obtain better performance than the S-type. In general, average operational torque (AOT) and torque ripple of IPM motors are greater than those of other permanent magnet motors due to reluctance torque. This reluctance torque is generated by permanent magnet arrangement in the rotor of IPM motor and causes noise and vibration. Therefore, this paper presents the optimal V-shape, based on the finite-element method, of permanent magnet in the V-type by robust design, called Taguchi method, to reduce torque ripple and improve the ratio between torque ripple and AOT than S-type. [ABSTRACT FROM AUTHOR]

Presents information on a study which analyzed the orbital response of rotor due to unbalanced electromagnetic force for Switched Reluctance Motor (SRM). Sources of vibration and noise in SRM; Analysis model and procedure; Analysis results and discussion; Conclusions.