Jae-Hak Choi

Hanyang University, Ansan, Gyeonggi, South Korea

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Publications (24)21.68 Total impact

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    ABSTRACT: The accurate determination of induction motor efficiency depends on the estimation of the five losses of stator and rotor copper loss, iron loss, mechanical loss and stray load loss. As the mechanical and stray load losses are not calculated by electro-magnetic analysis, the values of these two losses are very important in induction motor design. In this paper, the values of mechanical loss and stray load loss are proposed through investigating testing data from commercial products of three phase induction motors under 37kW. If the values of this paper are applied to motor design, the accuracy of design and analysis can be improved. The losses of motors are obtained by using load and no-load test results following IEC 60034-2-1 standard.
    Journal of Electrical Engineering and Technology 01/2014; 9(1). · 0.73 Impact Factor
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    ABSTRACT: This paper deals with the analysis techniques of a high speed and high efficiency 10 kW, 30,000 rpm rated induction motor. The induction motor has been analyzed by time-varying magnetic finite element method and the test results show that there is a possibility that the motor could be used in a high speed spindle system application. All analysis techniques are introduced to develop a high speed and high efficiency induction motor made by copper die casting. The analysis techniques are composed of magnetic analysis considering losses and input current (PWM and sinusoidal), structural analysis of rotor and stator, 3-D rotordynamic analysis and 3-D CFD. All performances of the prototype are successfully verified.
    IEEE Transactions on Magnetics 05/2013; 49(5):2319-2322. · 1.42 Impact Factor
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    ABSTRACT: The concentrated winding configurations offer significant advantage for reducing end windings. These machines are generally used in low speed high torque application due to relatively low copper loss. However, numbers of fractional slot construction make the designer hard to properly choose pole and slot numbers for the certain application. This paper provides the general information of possible fractional slot concentrated double layer winding machine.
    Journal of Electrical Engineering and Technology 01/2013; 8(2). · 0.73 Impact Factor
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    ABSTRACT: This paper deals with the analysis techniques of a high speed and high efficiency 10 kW, 30 000 rpm rated induction motor. The induction motor has been analyzed by the time-varying magnetic finite element method and the test results show that there is a possibility that the motor could be used in a high speed spindle system application. All performances of the prototype are successfully verified. All analysis techniques are introduced to develop a high speed and high efficiency induction motor made by copper die casting. The analysis techniques are composed of magnetic analysis, structural analysis, critical speed analysis, unbalance response analysis and computational fluid dynamics (CFD). CFD simulation results are compared with the experiment, and are within a 5% deviation.
    IEEE Transactions on Magnetics 01/2013; 49(7):4088-4091. · 1.42 Impact Factor
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    ABSTRACT: One of the advantages of interior permanent magnet synchronous motors compared to surface permanent magnet synchronous motors is its convenience when modifying the air gap flux density of permanent magnets. This paper introduces a technique of torque ripple reduction by modifying the shape of the rotor to modify the air gap flux density. Three types of rotor surfaces, such as conventional round, slightly cut, and smoothed cut shape, are investigated. The average torque, torque ripple, cogging torque, phase back-EMF, and air gap flux density distribution are analyzed and compared through finite element analysis (FEA). The validity of the proposed model is also verified by comparison between analysis results and measured results.
    IEEE Transactions on Magnetics 01/2011; 47(10):3240-3243. · 1.42 Impact Factor
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    ABSTRACT: Brushless permanent magnet DC motors are being manufactured and used increasingly in everything from home appliances to automobiles due to their inherent advantages. The merits of these motors could be enhanced further according to another design approach method which alters the typically used winding parts for low to medium power range motors. This paper deals with the high power brushless DC motor used for traction in a 48 V golf cart system. The stator is designed with segment rectangular copper winding to maximize output power within its limited dimensions. In the design process, the closed slot opening and slot-pole combination are investigated and compared in terms of efficiency and input current density. The developed motor obtained about 120% greater power density per volume compared to a commercial motor with round winding coils at similar efficiency and variable speed range.
    IEEE Transactions on Magnetics 07/2010; · 1.42 Impact Factor
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    ABSTRACT: This paper presents the novel method inductance calculation of a synchronous reluctance motor (SynRM). Synchronous inductances (Ld and Lq) are exceedingly important factor of SynRM to drive. Because of self axis current as well as the other axis current, inductances of d-axis and q-axis of SynRM are varied. Using an equivalent circuit model for expressing d-axis and q-axis inductance variation, the authors elicit suitable equation considering iron loss and cross magnetic saturation. Parameters of motor to use calculation are gained by AC signal test.
    IEEE Transactions on Magnetics 07/2009; · 1.42 Impact Factor
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    ABSTRACT: It is to make motors more efficient because of the higher conductivity of copper. In addition, reduced tosses in such motors may lead to better design flexibility and motors are more compact. However, copper price and weight is higher than aluminum so, copper wire motor has disadvantage compared with aluminum wire in manufacturing cost. This paper presents aluminum wire motor design to reduce motor manufacture cost and compares the cost with copper wire motor.
    01/2009;
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    ABSTRACT: This paper presents the design of some factors of three phase induction motor to maximize the efficiency using the design of experiments (DOE). The fractional factorial designs are used for the screening six design factors and the response surface methodology (RSM) is applied to get the efficiency-maximized points from the screened four factors. The design is also performed to consider the flux density of the stator and rotor teeth. The simulation based on equivalent circuit of induction motor is used to obtain the responses for DOE. From simulation results, the efficiency of the initial model can be improved by 3.3% without increasing motor volume and electrical steel grade.
    Electrical Machines, 2008. ICEM 2008. 18th International Conference on; 10/2008
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    ABSTRACT: The characteristics of an induction motor vary with the number of parameters and the performance relationship between the parameters also is implicit. In this article, the multiobjective optimization technique based on the genetic algorithm and sizing equation is applied for the three phase induction motor. The electromagnetic losses and the locked torque are selected for the objectives. The validity of the design results will be also clarified by comparison between calculated results and measured ones.
    Electrical Machines, 2008. ICEM 2008. 18th International Conference on; 10/2008
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    ABSTRACT: A lot of test methods to determine losses of induction motor have been proposed and standardized. Different countries around the world have been collected from those test method. In this paper, the differences among IEC 61972, 34-2 and IEEE 112-methodB are shown and testing results are also compared. The main discrepancies between the various standards are the way of quantification of the stray load losses (SLLs), the stator resistance at the load test and the core losses with the influence of the voltage drop compensation. To compare the differences according to standards, six induction motors with rated power 0.75 kW-7.5 kW are analyzed.
    Electrical Machines, 2008. ICEM 2008. 18th International Conference on; 10/2008
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    ABSTRACT: Electric motor efficient improvement from home appliance field is important to the effect reducing the energy consumption. But the electric motor design/analysis technology is still insufficient. Specially the electric motor design/analysis technology of satisfying characteristic of both the induction motor and the synchronous motor such as Line start permanent motor. Therefore the electric motor design/analysis technology is urgently demanded reliability. This paper proposes the sing1e-phase line-start permanent magnet motor to develop the motor it with be able to alternate the sing-phase induction motor it is a refrigerator compressor motor. The sing-phase induction motor is analyzed in the steady state. And we have a certification test to compare our single-phase line-start permanent magnet motor with the sing-phase induction motor. In order to improve the performance, the stator of the single-phase line-start permanent magnet motor is same as the stator of the sing-phase induction motor and changes the rotor form and has the permanent magnet. It used the Finite Element Method(FEM) which is widely used with electronic-magnetic field numerical analysis method.
    Journal of the Korean Institute of Illuminating and Electrical Installation Engineers. 01/2007; 21(3).
  • Jae-Hak Choi, J.S. Ahn, Ju Lee
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    ABSTRACT: This paper presents a characteristic analysis of the switched reluctance motor (SRM) considering freewheeling diode and dc-link voltage ripple by using time-stepped voltage-source finite-element method in which the magnetic field is combined with the drive circuit. The influence of freewheeling diodes and dc-link voltage ripple on the performance of an SRM such as torque ripples with switching modes is examined.
    IEEE Transactions on Magnetics 11/2005; · 1.42 Impact Factor
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    ABSTRACT: This paper presents a characteristic analysis of switched reluctance motor (SRM) considering hard chopping and dc link voltage ripple by using time-stepped voltage source finite element method in which the magnetic field is combined with drive circuit. We also examine the influence of freewheeling diodes and dc link voltage ripple on the performance of a SRM such as torque ripples and radial force on the surface of the teeth. The freewheeling diodes and dc link voltage ripples must be taken into account in predicting the performance of the SRM.
    IEEE Transactions on Magnetics 06/2005; · 1.42 Impact Factor
  • Jae-Hak Choi, Joonseon Ahn, Ju Lee
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    ABSTRACT: Time-stepped voltage source finite element method (FEM) was used as a computational method to analyze switched reluctance motor considering freewheeling diodes and dc link voltage ripples on hard and soft chopping modes respectively. The phase currents and the dc link voltage ripples were also measured for the first time
    01/2005;
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    ABSTRACT: In this paper, a multi-object optimization based on a progressive quadratic response surface method (PQRSM) and a time stepping finite element method (FEM) is proposed. The new PQRSM and FEM are able to decide optimal geometric and electric variables of the switched reluctance motor (SRM) with two objective functions: torque ripple minimization and average torque maximization. The result of the optimum design for SRM show an improved performance of motor and a relationship between torque ripple and average torque.
    Electrical Machines and Systems, 2003. ICEMS 2003. Sixth International Conference on; 12/2003
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    ABSTRACT: This paper deals with the characteristic analysis of a brushless dc motor (BLDC) taking into consideration the freewheeling diodes and dc link voltage ripple using a time-stepped voltage source finite-element method. By comparing the experimental results, the authors show that the proposed computational method is useful for the analysis and design of a BLDC motor. They also examine the influence of freewheeling diodes and dc link voltage ripples on the performance of a BLDC motor such as torque ripples and radial force on the surface of the teeth.
    IEEE Transactions on Magnetics 10/2003; · 1.42 Impact Factor
  • Jae-Hak Choi, Tae Heoung Kim, K.-B. Jang, Ju Lee
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    ABSTRACT: This paper presents an approximate optimization that is able to determine optimal geometric and electrical design variables of switched reluctance motor. In order to reduce torque ripple that causes noise and vibration, the approximate optimum design has been investigated by means of combining a progressive quadratic response surface method (PQRSM) and a time-stepping finite element method considering drive circuit. The PQRSM is more effective than conjugate gradient method in torque ripple minimization.
    IEEE Transactions on Magnetics 10/2003; · 1.42 Impact Factor
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    ABSTRACT: The design of anisotropic magnetic material is an important area of electromagnetic fields because these materials are used in not only motors but also in a large number of electromagnetic devices. This paper presents a new model that improves the inductance characteristic by using anisotropic iron-core material for the stator poles and isotropic iron-core material for the stator back iron and each rotor part. It is necessary to find expressions of correct behavior of B-H curves in the materials and an improved finite-element method considering the properties. To verify the proposed model, the new model is compared with the conventional model. As a result, it is shown that the new model has a good inductance and torque characteristic. Therefore, these affect the switched reluctance motor performance such as the torque density and peak torque.
    IEEE Transactions on Magnetics 10/2003; · 1.42 Impact Factor
  • Sol Kim, Jae-Hak Choi, Ju Lee
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    ABSTRACT: This article presents an optimal design for a single-phase line start synchronous motor according to permanent magnet and flux barrier geometries. To explore the improved torque and efficiency over that of conventional single-phase induction motors for compressors, three types of magnet shape and flux barrier are introduced. A time-stepped two-dimensional finite-element method that considers the external running capacitor is used for analysis of the steady state characteristics. Counter electromotive force at the rated speed, Ld and Lq inductances, torque, and efficiency are calculated to optimize the shape of the magnet and the flux barrier. From the torque and efficiency characteristics taking variation of the load angle into consideration in the steady state, we can determine an optimal design for the permanent magnet and the flux barrier. © 2003 American Institute of Physics.
    Journal of Applied Physics 05/2003; 93(10):8695-8697. · 2.21 Impact Factor