Jae-Hak Choi

The Seoul Institute, Sŏul, Seoul, South Korea

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Publications (31)23.94 Total impact

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    ABSTRACT: High speed induction motors have the different design parameters and loss distribution compared with line start induction motor because of various load conditions and inverter-fed supply voltage. Especially harmonic losses and mechanical losses must be considered severely. In order to check the variation of the design parameters in inverter-fed induction motor, these values are compared with those of line start induction motor (sinusoidal supply voltage) at same rated output power. The experimental results are verified through testing prototype of two types of 30 kW induction motor for loss analysis. The amount of harmonic loss is confirmed by calculating the loss differences between operating 4.5 kW induction motor from sinusoidal and inverter-fed supply voltage.
    16th International Symposium on Applied Electromagnetics and Mechanics; 01/2014
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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). DOI:10.5370/JEET.2014.9.1.121 · 0.52 Impact Factor
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    ABSTRACT: A copper die casting induction motor can obtain an energy saving effect of about 2-3% compared to previous aluminum die casing induction motors. In addition, copper die casting motors can reduce the size of motors and reduce material costs. The critical speed and unbalance response of high speed machines need to be verified by rotordynamic analysis for dynamic stability of the rotors. The critical speed analysis, harmonic analysis and transient analysis by unbalance are performed for dynamic stability. The unbalance analysis results are compared with the experiment considering allowable vibration displacement (API 611) and balancing grade (ISO 1940-1). This paper dealt with the design, analysis and experimental validation of a high speed induction motor. The dynamic stability of the prototype is verified successfully, and two experimental methods by ISO 10816-3 are suitable and reliable for the allowable vibration evaluation of rotating machine.
    International Conference on Manufacturing, Machine Design, and Tribology; 10/2013
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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 07/2013; 49(7):4088-4091. DOI:10.1109/TMAG.2013.2241033 · 1.21 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. DOI:10.1109/TMAG.2013.2242455 · 1.21 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 03/2013; 8(2). DOI:10.5370/JEET.2013.8.2.282 · 0.52 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 performances of the prototype are successfully verified. All analysis techniques are introduced to develop a high speed and high efficiency induction motor of copper die casting. The analysis techniques are composed of an electrical technique (magnetic analysis), and a mechanical technique (casting analysis, structural analysis, critical speed analysis and unbalance response analysis). Simulation results are compared with the experiment, and are within a 3% deviation.
    International Journal of Precision Engineering and Manufacturing 12/2012; 13(12). DOI:10.1007/s12541-012-0299-5 · 1.50 Impact Factor
  • Journal of Electrical Engineering and Technology 11/2012; 7(6):948-953. DOI:10.5370/JEET.2012.7.6.948 · 0.52 Impact Factor
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    ABSTRACT: A copper die casting motor (CDM) has better design flexibility than an aluminum die casting motor (ADM) because of the higher conductivity of copper. However, CDM has an economic and manufacturing weak point due to the high cost of copper and its high melting temperature compared to aluminium. This paper describes a comparison of the design parameters, specifications, performances and material cost between CDM and ADM of 2.2 kW_4P, 5.5 kW_4P, 7.5 kW_4P.
    15th International Symposium on Applied Electromagnetics and Mechanics; 01/2012
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    ABSTRACT: One of the major problems associated with interior permanent magnet machines is torque ripple, a problem that causes undesirable noise and possibly speed ripples. In this paper, rotor shaping near q-axis and its effects for torque ripple reduction are analyzed. Two new design variables are introduced for shaping the rotor pole. To verify the trade-off relationship between average torque and torque ripple by rotor pole shaping, the multi-objective optimization algorithm is employed to search the Pareto front of the problems. All results are obtained from 2D finite element analysis. The simulation results on two different lead angles are compared and the effect of rotor pole shaping is observed.
    15th International Symposium on Applied Electromagnetics and Mechanics; 01/2012
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    ABSTRACT: The approximate optimization based on a response surface modeling has been applied to the optimum design for obtaining flat torque of switched reluctance motor, which has high fluctuating torque due to its inherent salient structure. In order to reduce the fluctuating torque ripple causing noise and vibration, an optimization design technique has been introduced and investigated to find geometric and electric variables by means of combining finite element analysis considering driving circuits and response surface modeling. In this research an effective optimization method based on a response surface modeling has been used to overcome the modeling noise in formulating an objective and constraint and the cumulative numerical inaccuracy.
    15th International Symposium on Applied Electromagnetics and Mechanics; 01/2012
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    ABSTRACT: The characteristics of an induction motor vary depending upon the number of parameters and the performance relationship between the parameters is also implicit. In the case of the induction motor design, we should generally estimate the many objective physical quantities in the optimization procedure. In this article, the multi objective design optimization based on a genetic algorithm is applied for a three phase induction motor. The efficiency, starting torque, and material cost are selected as the objectives. The validity of the design results is also clarified by comparison between the calculated results and the measured ones.
    15th International Symposium on Applied Electromagnetics and Mechanics; 01/2012
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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 10/2011; 47(10):3240-3243. DOI:10.1109/TMAG.2011.2150742 · 1.21 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; 46(6-46):2070 - 2073. DOI:10.1109/TMAG.2010.2041908 · 1.21 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; DOI:10.1109/TMAG.2009.2018663 · 1.21 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.
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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: 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: 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.
    01/2007; 21(3). DOI:10.5207/JIEIE.2007.21.3.125