• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.64-66
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• 2004

Several techniques have been adopted in motor design of interior permanent magnet (IPM) type brushless DC (BLDC) motor to minimize cogging torque. IPM type motor has better ability in the centralization of flux than surface-mounted permanent magnet (SPM) type BLDC motor. So, the structure of IPM type BLDC motor has high saliency ratios that produce additional torque. However, this structure has a significant cogging torque that generates both vibration and noise. This paper describes new technique of the flux barriers design for reduction of cogging torque of IPM type BLDC motor. To reduce the cogging torque, flux barriers are applied in the rotor. Changing the number of barrier, the cogging torque is analyzed by finite clement method(FEM).

• 한국자동차공학회논문집
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• 제6권2호
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• pp.235-243
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• 1998

For motor operation at low speeds and loads, torque pulsation by the cogging torque is often a source of vibration and control difficulty. In this paper, the magnetic field of a motor is calculated by finite element method. The periodic cogging torque is determined using Maxwell stress method and time stepping method, and then decomposed using fourier series expansion, The purpose of this paper is to characterize design parameters on the cogging torque and to design a permanent magnet motor with a cogging torque less vulnerable to vibration, without sacrificing the motor performance. The design parameters include stator slot width, permanent magnet slot width, airgap length and magnetization direction. A new design with a less populated frequency spectrum of the cogging torque is proposed after characterizing individual effect of design parameters. Magnet pole edge shaping, by gradually increasing the cogging torque with reduced higher harmonics.

• Journal of Electrical Engineering and Technology
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• 제9권3호
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• pp.866-872
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• 2014

The purpose of this paper was to find an effective method for measuring electromagnetic torque produced by a brushless DC motor with single-phase current sensing in real-time. A torque equation is derived from the theory of brushless DC motor. This equation is then validated experimentally with a motor dynamometer. A computer algorithm is also proposed to implement the electromagnetic torque estimation equation in real-time. Electromagnetic torque is a linear function of phase current. Estimating the electromagnetic torque in real-time using single-phase current is not appropriate with existing equations, however, because of the rectangular alternating-pulse nature of the excitation current. With some mathematical manipulation to the existing equations, the equation derived in this paper overcame this limitation. The equation developed is simple and so it is computationally efficient, and it takes only motor torque constant and single-phase current to evaluate the electromagnetic torque; no other parameters such as winding resistances, inductances are needed. The equation derived is limited to the three-phase brushless DC motor. It can, however, easily be extended to the multiphase brushless DC motor with the technique described in this paper.

• Journal of Magnetics
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• 제22권2호
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• pp.266-274
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• 2017

In this paper, torques of two motors are compared by Finite Element Analysis (FEA). One has a symmetric rotor structure and the other has an asymmetric rotor structure. The comparison shows that the asymmetric rotor structured motor has reduced torque ripple compared to the symmetric. The torque of the compared motor models was analyzed by separating into magnetic torque and reluctance torque. Through the analysis of torque component separated, it is shown that the magnetic torque and the reluctance torque compensate each other in the motor with the asymmetric structure rotor. Here "compensate" means decrementing the effect of one or more harmonics. It is shown how this compensation appears between the magnetic torque and the reluctance torque by looking into back electro motive force (emf) and the relative permeability distribution of rotor core.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.67-69
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• 2004

This paper describes an approach to design a interior permanent magnet motor(IPM motor) for the reduction of cogging torque. The magnitude of the torque ripple and cogging torque in a interior permanent magnet motor(IPM motor) are generally dependent on several major factors: the shape of stator tooth tip, slot opening width, air gap length, the shape of barrier preventing flux leakage of magnets, magnet configuration and magnetization distribution or magnet poles. In this paper, the IPM BLDC motor is designed considering a saturated leakag flux between the barriers on the rotor for increasing the efficiency and decreasing the magnitude of the cogging torque. Analytical model is developed for the IPM BLDC motor with a concentrated winding stator. The results verifies that the proposed design approach is very efficient and effective in reducing the cogging torque and the torque ripple of the IPM BLDC motor to be used in an electric vehicle.

• Journal of Electrical Engineering and Technology
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• 제9권5호
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• pp.1569-1576
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• 2014

This paper mainly proposes a direct torque control strategy to minimize torque ripple in brushless DC (BLDC) motor. BLDC motor has large current and torque ripple when one voltage vector applied in one cycle due to its low inductance. Hence, this paper proposed a hysteresis torque control with PWM mode to control the resultant torque. Moreover, when the direct torque control system is operating during the two-phase half-bridge $120^{\circ}$ conduction mode, large torque ripple in commutation area appears every 120 electrical degree. Based on analyzing the root of torque ripple in detail, lookup tables of switching devices states for new half-bridge modulation mode in the positive and negative reference torque put forwarded. Finally, simulations by MATLAB software and experiment results from DSP are presented to verify the feasibility and effectiveness of the proposed strategy operating in four-quadrant operation.

• 전력전자학회논문지
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• 제3권1호
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• pp.23-35
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• 1998

영구자석 동기전동기의 제어에 있어서 토오크 맥동은 전동기 제어성능 결정에 큰 요인으로 작용한다. 본 논문에서는 이러한 토오크 맥동을 효과적으로 저감하기 위한 새로운 토오크 추정 및 제어기법에 대해서 다룬다. 제안된 기법에서는 모델 기준 적응시스템(Model reference adaptive system ; MRAS) 기법을 이용하여 순시 토오크를 추정하고 적본형 가변구 조제어(Integral variable structure control ; IVSC)를 이용하여 추정된 토오크를 제어한다. DSP를이용하여 고 토오크 영구자석 동기전동기 제어시스템을 구성하고 실험을 수행하였으며 그 결과 제안된 제어기법이 우수한 토오크 맥동 저감효과를 가짐을 입증하였다.

• 조명전기설비학회논문지
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• 제27권12호
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• pp.125-132
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• 2013

This paper has done a three-dimensional FEM analysis of the PM claw pole stepping motor. As magnetization happens in the z-axis, which does not have a constant value, three-dimensional FEM analysis is necessary for characteristic analysis of PM claw pole stepping motors. Because it is a type of permanent magnet motor, the PM claw pole stepping motor naturally has a detent torque. This torque is known to show negative effects on motor performance. To improve motor performance, reducing the detent torque is very important during the motor design. This paper applied DOE for optimization of stator pole design of the motor. Also, we compared motor performance by applying a different type of rotor shape, dividing the permanent magnet. To verify the simulation results, an experiment was done.

• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.118-127
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• 2015

This paper presents an advanced torque ripple minimization method of a switched reluctance motor (SRM) using torque sharing function (TSF). Generally, TSF is applied into the torque control. However, the conventional TSF cannot follow the expected torque well because of the nonlinear characteristics of the SRM. Moreover, the tail current that is generated at a high speed motor drive makes unexpected torque ripples. The proposed method combined TSF with fuzzy logic control (FLC). The advantage of this method is that the torque can be controlled unity at any conditions. In addition, the controller can track the torque under the condition of the wrong TSF. The effectiveness of the proposed algorithm is verified by the simulations and experiments.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권1호
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• pp.9-15
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• 2006

The conventional hysterysis band DTC(Direct Torque Control) strategy have relatively high torque ripple at low speed and variable switching frequency according to motor speed even though it provides a fast torque response with very simple scheme consisted with only two hysteresis band comparators and a switching table for torque and flux control. In this paper, author proposed a new DTC scheme based on the torque slope and reference voltage control. The new scheme can maintain the minimized torque ripple and constant switching frequency. Experimental tests carried out with an 1.5kW induction motor drive system show improved dynamic characteristics and prove the feasibility of proposed strategy.