• 조명전기설비학회논문지
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• 제28권4호
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• pp.49-55
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• 2014

In this paper, we propose the cogging toque reduction technique of the dual stator radial flux permanent magnet generator. The cogging toque is caused by the torque ripple increase and vibration and noise of the generator. And it is important factor determining cut-in speed of the small wind generator. To reduce cogging torque, permanent magnet displacement was studied. And the theory of the permanent magnet displacement was formulated and the cogging torque reduction according to the permanent magnet displacement was confirmed through the finite element method.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제12B권1호
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• pp.1-6
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• 2002

The severe problem in improving the positioning precision of a permanent magnet linear synchronous motor (PMLSM) is the large detent farce caused by the permanent magnet arrangement. It is generally an undesired effect that contributes to the torque ripple, vibration and noise of machine. The detent force is arisen from the difference of the position of a permanent magnet end and a tooth position. In this paper, the four methods to reduce detent force were studied and analyzed. The methods are adjusting the width of permanent magnet, varying the shape of armature teeth, relocating the permanent magnet, and adjusting the width of permanent magnet and relocating the permanent magnet at the same time. To analyze the detent farce according to flour methods, a two-dimensional Finite Element Analysis [FEA] was used and we compared with the ratio of reduction of the detent farce according to the flour methods.

• Journal of Power Electronics
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• 제6권4호
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• pp.290-297
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• 2006

Various methods have been discussed to reduce detent force in a tubular permanent magnet type linear single phase AC generator. In particular, the proposed methods depend on variations of the permanent magnet construction. These methods include two approaches in the form of sloped magnets, and conical magnets in addition to the conventional method of optimizing the magnet length. The undesired detent force ripples were calculated by a two dimensional Finite Element Method (FEM). Moreover, the generated electromotive force in the stator coils was calculated for each configuration of the permanent magnet. The experimental results agreed well with those obtained from the FEM-based simulations. Sufficient reduction in the detent force was achieved over the range of 40% while the root mean square of the output voltage was maintained. It was found that sloping the permanent magnet decreased the detent force and at the same time increased the generated rms voltage of the AC generator. The performance of the designed linear AC generator was evaluated in terms of its efficiency, total weight, losses, and power to weight ratio.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.1832-1837
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• 2011

This paper presents the optimal permanent magnet shape on the rotor of an interior permanent magnet motor to reduce the core losses and improve the performance. As permanent magnet has conductivity inherently, it causes huge amount of eddy current losses by the slot harmonics with concentrated winding. This loss is roughly 100 times larger than that of distributed winding in high speed operation and it cannot be ignored, especially on traction motors. Each eddy current loss on permanent magnet has been investigated in detail by using FEM(Finite Element Method) instead of EMCNM(Equivalent Magnetic Circuit Network Method) in order to consider saturation and non-linear magnetic property. Simulation-based DOE(Design Of Experiment) is also applied to avoid large number of analyses according to each design parameter and consider expected interactions among parameters. Consequently, the optimal design to reduce the core loss on the permanent magnet while maintaining or improving motor performance is proposed by an optimization algorithm using regression equation derived and lastly, the core loss reduction on the proposed shape of the permanent magnet is verified by FEM.

• 전기학회논문지
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• 제58권10호
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• pp.1930-1935
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• 2009

This paper deals with the torque ripple reduction of permanent magnet synchronous motor using harmonic current injection. Torque ripple of electric motor reduces system stability and performances, therefore efforts to reduce torque ripple are exerted in the design process. Torque ripple can be reduced by appropriate pole/slot combination, skew of rotor or stator, design of magnetic circuit, etc. In addition, torque ripple can be also reduced by input voltage and current, and many researches have been conducted to reduce torque ripple for six-step drive. Torque ripple reduction for current vector controlled permanent magnet synchronous motor also have been conducted and verified by investigating back emf wave form. Torque ripple reduction in this paper started from getting torque profile according to input current and electrical angle calculated by FEA, then instantaneous currents at each electrical angles for constant torque are calculated and applied to experiments. Therefore, 0% of torque ripple can be obtained theoretically with harmonic current injection. In order to maximize the effect of torque ripple reduction, a BLDC motor having high harmonic component of back emf is chosen. With sinusoidal current drive, over 100% of torque ripple is obtained initially, then 0.5 % of torque ripple is obtained by FEA using harmonic current injection. The effect is verified by experiment and the presented method can be effectively applicable to Electric Power Steering(EPS).

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 B
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• pp.757-759
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• 2000

The problem in improving the positioning precision of a permanent magnet linear synchronous motor(PMLSM) is the large detent force caused by the permanent magnet. The detent force is thought to arise from the difference of the position of a permanent magnet end and a tooth position. In this paper, Three methods of reducing detent force is presented The first method is adjusting the width of permanent magnet. The second method is varying the shape of armature teeth. The third method is the arrangement of the permanent magnet end. This paper compares with the ratio of reducing the detent force according to the three methods.

• 전기학회논문지
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• 제57권12호
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• pp.2208-2212
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• 2008

This paper deals with the cost reduction design of a single-phase line-start permanent magnet(LSPM) motor. Due to high cost of the permanent magnet(PM), cost reduction can be effectively achieved by reducing PM volume. Therefore, motor characteristics according to the PM volume are calculated by using d-q axis equivalent circuit analysis, and the characteristic map is made. In the characteristic map, maximum torque and efficiency are shown according to motor parameters such as back electromotive force(back emf) and inductances; back emf represents the PM volume. Minimum back emf and inductances satisfying output performance are determined in the characteristic map. Then, motor geometry based on the prototype motor is optimized to get the determined parameters using response surface methodology(RSM) and finite element method(FEM). Through the presented cost reduction design, total PM volume is reduced to 32% of prototype model.

• 조명전기설비학회논문지
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• 제24권8호
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• pp.27-31
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• 2010

EPS(Elctrical Power Steering)에서 전동기의 토크 리플은 조향장치의 진동 문제를 야기한다. 따라서 EPS에서 전동기의 토크 리플 저감은 중요한 문제이며, 본 논문에서는 EPS에서 사용하는 표면부착형 영구자석 동기전동기의 토크 리플 저감에 대해 논하였다. 유한요소법을 이용하여 영구자석과 고정자 슈의 형상 변화를 통해 역기전력을 분석하였으며 이를 바탕으로 토크 리플 저감 방안을 제시하였다.

• 전기학회논문지
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• 제57권3호
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• pp.390-397
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• 2008

Permanent Magnet Linear Synchronous Motor (PMLSM) has high efficiency, high energy density, and high control-ability. But, the detent force always is produced by the structure of slot-teeth. There are the disadvantages such as noise and vibration of the apparatuses are induced and the control ability is curtailed because detent force acts as thrust ripple. Therefore, the detent force reduction is an essential requirement in PMLSM. Generally, the method, skewing permanent magnet or slot-teeth, is used to reduce the detent force. But the thrust is decreased at the same time. If permanent magnet is skewed, the lateral force which operates as the perpendicular direction of skew direction is generated in linear guide of PMLSM. So, V-skew model is proposed for the reduction of lateral force. The lateral force acts as braking force in linear motion guide, and it has bad influence to the characteristics of PMLSM. However, these problems will not be solved by 2-dimensional Finite Element Analysis (FEA). So, in this paper 3-dimensional FEA is applied to analyze the PMLSM where permanent magnet is skewed and has overhang. The detent force and thrust characteristics considering skew and overhang effects of permanent magnet are analyzed by 3-dimensional FEA and the results are compared with experimental values to verify the propriety of analysis.

• Journal of Electrical Engineering and Technology
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• 제11권4호
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• pp.878-888
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• 2016

Cogging torque has a negative impact on the operation of permanent magnet machines by increasing torque ripple, speed ripple, acoustic noise and vibration. In this paper Magnet Shifting Method has been used as a tool to reduce the cogging torque in inset Line Start Permanent Magnet Synchronous Motor (LSPMSM). It has been shown that Magnet Shifting Method can effectively eliminate several lower-order harmonics of cogging torque. In order to implement the method, first the expression of cogging torque is studied based on the Fourier analysis. An analytical expression is then introduced based on Permanent Magnet Shifting to reduce cogging torque of LSPMS motors. The method is applied to some existing machine designs and their performances are obtained using Finite Element Analysis (FEA). The effect of magnet shifting on pole mmf (magneto motive force) distribution in air gap is discussed. The side effects of magnet shifting on back-EMF, core losses and torque profile distortion are taken into account in this investigation. Finally the experimental results on two prototypes 24 slot 4 pole inset LSPMS motors have been used to validate the theoretical analysis.