• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권1호
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• pp.1-6
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• 2002

Cogging torque is often a principal source of vibration and acoustic noise in high precision spindle motor applications. In this paper, cogging torque is analytically calculated using energy method to show that Fourier spectra of airgap permeance function and airgap MMF function are the most important design parameters to control cogging torque. To control these functions, stator pole shoe pairing and magnet arc design are proposed to minimize cogging torque. As for optimization technique, genetic algorithm is applied to handle trade-off effects of design parameters. Results show that the proposed method can reduce the cogging torque effectively.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권3호
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• pp.97-103
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• 1999

This paper investigates reduction of acoustic noise and cogging torque in a BLDC motor with larger stator slot open width. Using energy method, cogging torque is analytically determined with airgap MMF function and airgap permeance function and confirmed by FEM analysis. It shows that the cogging torque is firstly governed by NL GNL BNL with the fundamental period of NL, where NL is the least common multiple of the number of slots and the number of poles, GNL, airgap permeance function and BNL, airgap MMF function. It also shows that there exist several tooth width which minimizes the cogging torque, for the motors that smaller slot open width or stator teeth notching is not available. And it proposes a teeth pairing with two different tooth width which can effectively eliminate the cogging torque and thus the acoustic noise. Experimental results show that the proposed teeth pairing reduces the cogging torque by 85% and the acoustic noise by 3.1dB.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 추계학술대회 논문집 학회본부
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• pp.19-22
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• 1990

In this paper, in order to reduce the cogging torque in a permanent motor, a method to optimize the shape of permanent magnet and iron pole is presented. Because the cogging torque comes from the irregular system energy variation according to the rotor position, system energy variation is taken as object function and the object function is minimized to optimize the shape. The positions of permanent magnet surface and iron pole surface are chosen as design parameters and sensitivity of object function with respect to design parameter is calculated. The shape is changed according to sensitivity. Sensitivity can be generated by methods that exploit the FEM formulation. A numerical example shows that about 90% of the original cogging torque is reduced.

• 대한전기학회논문지
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• 제39권12호
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• pp.1246-1252
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• 1990

In order to reduce the cogging torque in a permanent magnet motor, a method to optimize the shape of permanent magnet and iron pole is presented. Sine the cogging torque comes from the irregular system energy variation according to the rotor position, system energy variation is taken as object function and the object function is minimized to optimize the shape. The positions of permanent magnet surface and iron pole surface are chosen as design parameters and sensitivity of object function with respect to the design parameter is calculated. The shape is changed according to sensitivity can be generated by methods that exploit the FEM formulation. A numerical example shows that the cogging torque is reduced to about 10% of the original value.

• 전기학회논문지
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• 제57권6호
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• pp.959-965
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• 2008

This paper presents a novel method for cogging torque reduction of interior type permanent magnet motor. For calculation position and width of notch, energy formulation and cogging torque function in air gap are analyzed by analytical method(space harmonics method) and numerical method. The optimal shape of notchs is decided by using finite element method. The validity of the proposed method is confirmed with experiments.

• 전기학회논문지
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• 제58권4호
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• pp.735-741
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• 2009

This paper presents an algorithm for the permanent magnet shape optimization of a large scale BLDC(Brushless DC) motor to minimize the cogging torque. A response surface method (RSM) using multiquadric radial basis function is employed to interpolate the objective function in design parameter space. In order to get a reasonable response surface with relatively small number of sampling data points, additional sampling points are added on the basis of design sensitivity analysis computed by using FEM. The algorithm has 2 stages: the first stage is to determine the PM arc angle, and the 2nd stage is to optimize the magnet pole shape. The developed algorithm is applied to a 5MW BLDC motor to get a minimum cogging torque. After 3 iterations with 4 design parameters, the cogging torque is reduced to 13.2% of the initial one.

• Journal of Electrical Engineering and Technology
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• 제1권4호
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• pp.466-471
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• 2006

This raper presents a new optimization method combining the genetic algorithm with the response surface method for the optimum design of a Brushless Direct Current motor. The method utilizes a regression function approximating an objective function and the window moving and zoom-in method so as to complement disadvantages of both the genetic algorithm and response surface method. The results verify that the proposed method is powerful and effective in reducing cogging torque by optimizing only a few decisive design factors compared with the conventional stochastic methods.

• 대한전기학회논문지
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• 제40권7호
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• pp.643-655
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• 1991

The analysis method on air gap permeance distribution, air gap MMF distribution, air gap flux density distribution, cogging torque and BEMF about the skewed stator slots or the skewed rotor magnet segments for BLDCM, respectively, is studied as a function of the skew ratio. The proposed method describes the differences between the skewed stator slots and teh skewed rotor magnet segments for the air gap permeance distribution, air gap MMF distribution and air gap flux density distribution. The reliability of the method is also confirmed by the waveform of the cogging torque and BEMF through experiments. And the result shows that the effects on the cogging torque and BEMF due to the skewed stator slots or the skewed rotor magnet segments are the same. In case of the skewed stator slots, the effects of the variations of the winding resistance and inductance are also studied.

• 한국자기학회지
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• 제24권5호
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• pp.160-164
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• 2014

본 논문에서는 설계변수의 불확실성을 고려한 BLDC 전동기의 코깅 토크 저감 설계를 수행하기 위하여 개선된 다구찌법을 이용한 효율적인 강건 최적설계 기법을 제안하였다. 일반적인 강건 최적설계 문제를 처리할 때 발생하는 기존 다구찌법의 단점을 해결하기 위하여, 벌칙함수와 최적수준 탐색기법이 새로이 도입되었다. 제안된 설계기법의 타당성을 검증하기 위하여 5 kW, 정격속도 2,300 rpm, 정격 토크 20 Nm의 전기자동차 구동용 BLDC 전동기의 코깅 토크 저감을 위한 강건 설계가 수행되었다. 또한 도출된 설계결과를 코깅 토크, 정격 토크 및 토크 리플에 대해 개념설계와 결정론적 최적설계 된 전동기들의 결과와 비교하였다.

• Journal of Electrical Engineering and Technology
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• 제9권3호
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• pp.859-865
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• 2014

Optimization of an electric machine is mainly a nonlinear multi-modal problem. For the optimization of the multi-modal problem, many function calls are required with much consumption of time. To address this problem, this paper proposes a novel hybrid algorithm in which function calls are less than conventional methods. Specifically, the proposed method uses the kriging metamodel and the fill-blank technique to find an approximated solution in a whole problem region. To increase the convergence speed in local peaks, a parallel gradient assisted simplex method is proposed and combined with the kriging meta-model. The correctness and usefulness of the proposed hybrid algorithm is verified through a mathematical test function and applied into the practical optimization as the cogging torque minimization for an interior permanent magnet synchronous machine.