Kyu-Seob Kim

Temperature Estimation of IPMSM Using Thermal Equivalent Circuit

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.

Optimum Shape Design of Single-Sided Linear Induction Motors Using Response Surface Methodology and Finite-Element Method

This paper deals with finding the optimal ratio of height and length of Single-Sided Linear Induction Motors (SLIM) using Finite Element Method (FEM) for magnetic field analysis coupled with optimal design methodology. For effective analysis, FEM is conducted in time harmonic field which provides steady state performance with the fundamental components of voltage and current. The ratio of height to length providing the required output power is obtained by Response Surface Methodology (RSM) and optimal values are presented by the variation in output power. When output power is small, the ratio is high and as the power increases, the ratio shows a converged value. Considering the general application of linear motors, using a small ratio can be limiting, however, the shape ratio for maximum thrust can be identified.

Reliability-Based Robust Design Optimization With Kernel Density Estimation for Electric Power Steering Motor Considering Manufacturing Uncertainties

Reliability-based robust design optimization (RBRDO) is a notable method to secure the quality and feasibility of performances from uncertainties. In this paper, geometric uncertainties of a stator sheet that can occur during a stamping process are considered as the uncertainty of controllable variables. Then, as the uncertainty of uncontrollable variables, skew angle due to inexact lamination is considered. No researches on the effect of this uncertainty have been performed. To analyze the effects of the uncertainties, the kernel density estimation (KDE) was employed to estimate the distribution because of its convenience, flexibility, and robustness. Then, RBRDO with the KDE is performed and the optimum results are compared with real data measured from manufactured motors.

Water-Cooled Direct Drive Permanent Magnet Motor Design in Consideration of its Efficiency and Structural Strength

This paper deals with a water-cooled direct drive permanent magnet (DD-PM) motor design for an injection molding application. In order to meet the requirements for the target application and consider the practical problems of the manufacturing industry, the DD-PM motor is designed in consideration of efficiency and structural strength with many constraints. The performances of the designed motor are estimated not only by magnetic field analysis, but also by thermal and structural analysis. The design and analysis results are presented with experiment results.

Thickness effects on magnetic properties and ferromagnetic resonance in Co–Ni–Fe–N soft magnetic thin films

In this study, the magnetic properties and microstructures have been investigated in Co–Ni–Fe–N soft magnetic thin films with various film thicknesses (0.01–1.0 μm). As the film thickness decreases, the coercivity, electrical resistivity, and magnetic anisotropy field of these films increases from 1.1 to 7.9 Oe, 53 to 188 μΩ cm, and 20 to 70 Oe, respectively. In addition, excellent high frequency characteristics were achieved in Co–Ni–Fe–N films with thicknesses less than 0.3 μm, where an effective permeability of, ∼1000 was maintained out to 700 MHz. Analysis results from XRD, TEM, and FMR show that a 0.1-μm-thick film is composed of an amorphous phase. This amorphous phase gradually changes to a crystalline phase with increasing film thickness.

Thermal Analysis of Water Cooled ISG Based on a Thermal Equivalent Circuit Network

Recently, the interior permanent synchronous motor (IPMSM) has been applied to an integrated starter and generator (ISG) for hybrid electric vehicles. In the design of such a motor, thermal analysis is necessary to maximize the power density because the loss is proportional to the power of a motor. Therefore, a cooling device as a heat sink is required internally. Generally, a cooling system designed with a water jacket structure is widely used for electric motors because it has advantages of simple structure and cooling effectiveness. An effective approach to analyze an electric machine with a water jacket is a thermal equivalent network. This network is composed of thermal resistance, a heat source, and thermal capacitance that consider the conduction, convection, and radiation. In particular, modeling of the cooling channel in a network is challenging owing to the flow of the coolant. In this paper, temperature prediction using a thermal equivalent network is performed in an ISG that has a water cooled system. Then, an experiment is conducted to verify the thermal equivalent network.

Magnetic properties and reliabilities of FeXN (X=Ti,Al,Hf,CoHf,CrHf) nanocrystalline thin film head materials

A series of FeN and FeXN (X=Ti,Al,Hf,CoHf,CrHf) films were prepared by reactive RF magnetron sputtering. These FeXN films exhibit good soft magnetic properties with low coercivity (<2 Oe) and high moment (15-20 kG). To investigate the reliability of these films, we performed the thermal stability and electrochemical corrosion test for pure Fe, Permalloy, FeN and FeXN films. The results show that the direction of the magnetic anisotropy of FeTiN, FeCoHfN and FeCrHfN is not nearly changed by the DC magnetic field of 100 Oe perpendicular to the easy axis at 150/spl deg/C, for up to 3 hrs. The electrochemical corrosion tests were performed in 0.5 M NaCl electrolyte. Permalloy shows the best corrosion resistance in the films but the addition of Cr to FeHfN films significantly improves the corrosion resistance, to be nearly as good as Permalloy. This improvement results from the formation of a negative oxide layer.

Reliability-Based Optimum Tolerance Design for Industrial Electromagnetic Devices

Principle of tolerance design is receiving increased research focus to determine the optimal tradeoff between manufacturing cost and quality. However, current tolerance designs are not suitable for products such as electromagnetic devices that require high reliability, i.e., a very low failure rate. In this paper, a new tolerance design named as reliability-based optimum tolerance design is formulated and performed to guarantee the high reliability of the products while maximizing manufacturing tolerances. The proposed method quantifies the reliability using reliability analysis, which reflects the tolerance in the tolerance design. To validate the proposed method, tolerance design is applied to two examples: 1) a magnetic circuit ( C -core) and 2) a mass-produced interior permanent magnet motor that contains manufacturing tolerances of permanent magnet.

Improvement of Thermal Equivalent Circuit Network and Prediction on Heat Characteristic of Motor by Calculation of Convection Heat Transfer Coefficient

According to miniaturization, estimation of motor temperature is necessary, and many approaches are developed. Irreversible demagnetization occurred by change of permanent magnet temperature and increase in resistance are affected by temperature increase in motor due to the losses. In this paper, the temperature of motor is calculated by applying equivalent thermal circuit network. Thermal source, thermal resistance and thermal capacitor which are components of thermal equivalent circuit network are calculated and equivalent circuit is composed considering heat transfer in motor. Especially computation for heat transfer of convection is important. The prediction of temperature in existing thermal equivalent circuit is improved by more accurate calculation of heat transfer coefficient considering components of natural convection and forced convection.

The effect of Cr addition on structure and corrosion resistance in FeTiN nanocrystalline soft magnetic thin films

FeTiN and FeCrTiN thin films were prepared by reactive rf magnetron sputtering. Fe/sub 92.3/Ti/sub 2.1/N/sub 5.6/ (at.%) films showed excellent thermal stability and soft magnetic properties; saturation magnetization (4/spl pi/M/sub s/)/spl sim/19.5 kG, coercivity (H/sub c/)/spl sim/1.2 Oe and effective permeability (/spl mu//sub eff/)/spl sim/2000 at 100 MHz. However, the corrosion resistance behaviors of the FeTiN films were similar to those of other FeMN films. For improving the corrosion resistance of the FeTiN films without the deterioration of magnetic properties, Cr was added to the FeTiN films. In an as-deposited Fe/sub 90.3/Cr/sub 1.2/Ti/sub 1.1/N/sub 7.4/ film, the permeability reached about 2700 at 100 MHz and 4/spl pi/M/sub s/ and H/sub c/ showed /spl sim/18.6 kG and 1.5 Oe, respectively. From XRD and TEM results, the sizes of /spl alpha/-Fe grains in the FeTiN and FeCrTiN films were observed to be below 10 nm and the grain orientations of the FeCrTiN films were more evenly distributed than the FeTiN films. Also, an addition of Cr in FeTiN films improved the corrosion resistance without the deterioration of soft magnetic properties on FeCrTiN films, caused by the formation of passivation layers in their surface.