Jae-Han Sim

Optimum design of SPMSM with concentrated windings and unequal tooth widths for EPS

Cogging torque and torque ripple of surface-mounted permanent magnet synchronous motor applied to electric power steering (EPS) have been one of the main concerns in manufacturing the EPS system. A variety of methods have been suggested to minimize cogging torque and torque ripple. However, this paper presents 2 different types of the motor and a comparative result from their characteristic analyses using finite element method. Both are composed of 8 poles/12 slots with concentrated windings while one have equal tooth widths and the other unequal tooth widths. Furthermore, it is scarcely possible to induce equations which express the relations among the 4 design parameters, eccentricity, angle between tooth tips, small tooth width, and pole arc. Therefore, this paper purposes optimization of unequal type for EPS motor through response surface methodology.

Advanced Method of Selecting Number of Poles and Slots for Low-Frequency Vibration Reduction of Traction Motor for Elevator

This paper presents an advanced method of selecting the number of poles slots so as to reduce the vibration of a traction motor for a gearless elevator system. The vibration source, i.e., the radial electromagnetic force, of the prototype was examined through its analytical derivation. The expression indicated the vibration orders and frequencies of the radial electromagnetic force that was caused by the interactions within or between armature reaction and permanent magnet fields including the stator slotting effect. More specifically, the prototype with 14 poles and 18 slots displayed a problem in terms of the vibration at the two times line frequency; this was due to the lowest vibration order 2. The vibration at two times line frequency was decreased by approximately 77.27% through a selection of 24 poles and 54 slots with a lowest vibration order of 6. A tower test was then conducted in order to validate the proposed method. Finally, an experiment on models having other rated load and pole-slot combinations was also carried out to improve the overall reliability.

Temperature prediction of oil-cooled IPMSM for in-wheel direct-drive through lumped parameter thermal model

This paper focuses on estimating the temperature of end winding, in which the highest temperature exists out of all the components, in Interior Permanent Magnet Synchronous Motor (IPMSM) for in-wheel direct drive. A lumped parameter thermal model of IPMSM is suggested with considering core, copper, mechanical, and eddy current losses, which are the heat sources and calculated from finite element analysis to improve the accuracy of the prediction. In addition, the thermal model is comprised of thermal resistances and capacitances determined by the configurations and the dimensions of motor. Finally, an oil-cooling system is covered with the concepts of thermal conductivity, density, specific heat at constant pressure, dynamic viscosity, and flow rate.

Analytical Electromagnetic Modeling and Experimental Validation of Vehicle Horn Considering Skin Effect in Its Solid Cores

This paper presents an analytical modeling of axisymmetric vehicle horn, considering its skin effect in solid cores, based on coupled electromagnetic circuit. The vehicle horns usually use the solid cores for mass production and cost reduction. Such cores, however, induce high eddy current loss and low inductance when exposed to a time-varying magnetic field. The high eddy current loss and low inductance eventually make it difficult to estimate the performance of the vehicle horn and figure out which design variables have a positive or negative effect on it. Thus, the coupled circuit reflects not only the skin effect of the electromagnetic fields, which travel in the conductive media, but also their nonlinear magnetization curves. The concept “coupled” was introduced to calculate the magnetic flux and the back electro-motive force by determining the magnetizing current in the electric circuit and the reluctance in the magnetic circuit. Furthermore, the analytical approaches to the equivalent iron loss resistance and the inductance were also investigated. Finally, a prototype was manufactured, experimented, and compared with finite-element analysis data to validate the aforementioned method.

3-D Equivalent Magnetic Circuit Network Method for Precise and Fast Analysis of PM-Assisted Claw-Pole Synchronous Motor

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.

Analytical modeling and experimental verification of vehicle horn considering skin effect using coupled electric and magnetic circuits

This paper presents an analytical modeling of an axisymmetric vehicle horn considering skin effect in solid cores based on coupled electric and magnetic circuits. The vehicle horns usually use the solid cores for mass production and cost reduction, but such cores induce high eddy current loss and low inductance. That makes it difficult to estimate the performances of the vehicle horn because of high iron loss current. Thus, the coupled circuits reflect the skin effect of the electromagnetic waves, which travel in conducting mediums under a time-varying field, as well as the nonlinear magnetization curves. The concept “coupled” is introduced to determine the magnetic flux and the back electro-motive force through analyzing the effective current in the electric circuit and the system reluctance in the magnetic circuit. In addition, the analytical approaches to equivalent iron loss resistance and inductance are also presented. Finally, the prototype is tested to validate the aforementioned method.

3-D equivalent magnetic circuit network for precise and fast analysis of PM-assisted claw-pole synchronous motor

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 motor has an axially asymmetric rotor configuration, which induces the corresponding 3-D magnetic field distribution. Thus, this paper develops an infinitesimal hexahedron-element-based 3-D equivalent magnetic circuit network (EMCN) to estimate the performance of the PM-assisted CPSM. The hexahedron element can be considered as an optimum unit element in describing the configuration of the PM-assisted CPSM in detail. That eventually makes it possible to analyze the specific 3-D magnetic field distribution from which the flux-linkage, the back-electro motive force, the d-and q-axis inductances, and the electromagnetic torque are also being calculated. The results from the 3-D EMCN are compared with those from the 3-D FEA and/or the experiment so as to validate the accuracy. Finally, it is proved that the 3-D EMCN requires a shorter computing time than the 3-D FEA.

Torque improvement of wound field synchronous motor for electric vehicle by PM-assist

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 permanent magnet assist is dependent on the inserted position of the permanent magnets. Thus, four models whose permanent magnets are inserted at each different positions are suggested. Then, the most effective position of the permanent magnet is decided by the mean torque per employed amount of the permanent magnet. By inserting the permanent magnets 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.

Optimum design of IPMSM for in-wheel direct-drive by response surface methodology and FEA

In-wheel system is indispensible in eco-friendly vehicles including hybrid and fuel cell vehicles in regard to fuel consumption and degree of freedom. This paper focuses on designing and optimizing an Interior Permanent Magnet Synchronous Motor (IPMSM) for the system with the goals of minimizing torque ripple and Total Harmonic Distortion (THD) of line-to-line Back Electro-Motive Force (BEMF) through response surface methodology and finite element analysis since it is rarely possible to induce the equations which express the relationships between the design parameters and the objective functions. In addition, the IPMSM is comprised of 8 poles and 48 slots considering vibration and noise order, which is strongly connected to the magnitudes of torque ripple and THD of line-to-line BEMF. Particularly, the figures of barriers installed on both sides of magnets in rotor play the main role in satisfying the targets. In conclusion, the results from finite element analysis are compared with those from experiment to prove the validity. Having a lower torque ripple and THD of line-to-line BEMF, the optimum model is anticipated to show a lower degree of vibration and noise while the electromagnetic performances such as average torque and output power are maintained at the same with the prototype.