• Title, Summary, Keyword: Cogging torque

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Sensitivity Analysis of Design Parameters for Reduction of Cogging Torque in Brushless DC Motors used for Automobile Part (자동차 부품용 BLDC 모터 내의 코깅 토크 저감을 위한 설계 변수의 민감도 해석)

  • 황상문
    • Transactions of the Korean Society of Automotive Engineers
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    • v.6 no.2
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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.

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Design of Cogging Torque and Torque Ripples Reduction for High Precision Controlled SPMSM (정밀제어용 표면부착형 영구자석 동기전동기의 코깅토크 및 토크리플 저감 설계)

  • Kim, Chang-Ki;Lee, Sang-Gon;Jung, Sang-Yong
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.10
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    • pp.1923-1929
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    • 2009
  • The design of SPMSM(surface mounted permanent magnet synchronous motor) has been performed to reduce cogging torque and torque ripples. In general, cogging torque and torque ripples are affected by the shapes of teeth width, yoke depth, magnet pole arc, etc. Particularly, the minimum design point of cogging torque and torque ripples are different so that the design of SPMSM should be done to compromise both of them for precision application. In this paper, the design of PMSM for EPS(electric power steering) system is performed to verify the validity, and the design characteristics versus teeth width, yoke depth, and magnet pole arc are investigated in order to find out the minimum point of cogging torque and torque ripples. In addition, skew of PM is applied for cogging torque reduction.

Cogging Torque Minimization in Permanent Magnet Brushless DC Motors for High-Speed Application

  • Jang Seok-Myeong;Cho Han-Wook;You Dae-Joon
    • KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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    • v.5B no.2
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    • pp.146-153
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    • 2005
  • In a permanent magnet brushless dc motor, cogging torque is produced by the magnetic attraction between the rotor mounted permanent magnets and the stator teeth. This always produces a pulsating torque ripple resulting in vibration and acoustic noise, which is detrimental to the motor performance. This paper deals with the analytical prediction of cogging torque and the various cogging torque minimization techniques as applied to a permanent magnet brushless dc motor.

Optimal Design of Stator of Permanent Magnet Motors Having Closed Slot For The Cogging Torque Reduction (폐슬롯 형상을 가진 영구 자석형 동기 전동기의 코깅 토크 저감을 위한 고정자 치수 최적화)

  • Chun, J.S.;Hong, S.K.;Yoon, J.S.;Jung, H.K.
    • Proceedings of the KIEE Conference
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    • pp.59-61
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    • 1995
  • This paper presents the cogging torque analysis of the permanent magnet type AC servo motor which have the closed slot structure. Generally, existence of the slot opening causes the cogging torque. But the cogging torque exists in this type motor(having closed slot structure) because the bridge part is saturated by the rotor flux. In this paper, the finite element analysis is used to calculate the cogging torque and the rated torque. As the size of the bridge part-the thickness and the width-changes, the cogging torque and the rated torque are obtained repeatedly like as upper procedures. Finally, the trends of the cogging torque and the rated torque versus the size of the bridge part are obtained from this analysis procedures. By this approach, the optimal geometry of the bridge part can be found which minimize the cogging torque satisfying the required value of the rated torque.

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Reduction and Analysis for Cogging Torque of Permanent Magnet Synchronous Generators with Multi-Pole Rotor for Wind Power Application (풍력발전용 영구자석 다극 동기발전기의 코깅토크의 해석 및 저감)

  • Jang, Seok-Myeong;Lee, Sung-Ho;Choi, Jang-Young
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.57 no.3
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    • pp.375-383
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    • 2008
  • This paper deals with reduction and analysis of cogging torque for permanent magnet synchronous generators with multi-pole rotor for wind power applications. Open-circuit field solutions are derived using a magnetic vector potential and a two-dimensional (2-d) polar coordinate systems. On the basis of derived open-circuit field solutions and 2-d permeance functions, we also derive open-circuit field solutions considering stator slotting effects. By using open-circuit field solutions considering stator slotting effects and energy variation methods, this paper analytically predicts the cogging torque considering skew effects. All analytical results are shown in good agreement with those obtained from finite element (FE) analyses. In order to reduce the cogging torque, by predicting the variation of the cogging torque according to pole arc/pitch ratio using analytical and FE methods, pole arc/pitch ratio which makes the cogging torque minimum are determined. However, we confirm that measured value for cogging torque of the PMG with determined pole arc/pitch ratio is twice higher than predicted value. Therefore, the reason for an error between measured and predicted cogging torque is discussed in terms of a shape of PMs and is proved experimentally.

Design Techniques for reduction of Cogging Torque in Brushless DC Motors used for Electric Power Steering (전기 조향 장치용 BLDC 모터 내의 코깅 토크 저감을 위한 설계 기술 개발)

  • 황상문
    • Transactions of the Korean Society of Automotive Engineers
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    • v.6 no.3
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    • pp.106-114
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    • 1998
  • Cogging torque is often a principal source of vibration and control difficulty in permanent magnet motors, especially at low speeds and loads. For example, reduction of cogging torque is an important specification for DC motors used for electric power stee- ring. This paper examines two motor design techniques, stator tooth notching and rotor pole skewing with magnet pole shaping, for reduction of cogging torque, and the effect of each method on the airgap flux, and the use of the Maxwell stress method and Fourier decomposition to calculate the periodic cogging torque. The analyses show that the cogging torque can be nearly eliminated by the suggested designs, with minimal scacrifice of output torque.

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Design Techniques for Reducing Cogging Torque in Permanent Magnet Flux Switching Machine

  • Wang, Daohan;Wang, Xiuhe;Jung, Sang-Yong
    • Journal of Magnetics
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    • v.18 no.3
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    • pp.361-364
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    • 2013
  • Permanent magnet flux switching motor (PMFSM) is a novel double salient machine which employs PMs instead of field winding for excitation. PMFSM contains only one set of armature winding, thereby features simple control strategy, low cost power inverter and substantial high efficiency. Due to the unique double salient structure and operation principle, the generated cogging torque in PMFSM is critical and quite different compared to the traditional PM machines. This paper presents and investigates various design techniques for reducing cogging torque in PMFSM. Firstly, an analytical model is proposed to study the influence of different methods on cogging torque. Then the optimal design parameters for minimizing cogging torque are determined by the analytical model, which significantly reduces the computational efforts. At last, the cogging torque with different design approaches are simulated by FEA along with the average output electromagnetic torque, which validates the analysis above.

Minimization of Cogging Torque in Permanent Magnet Motors by Stator Pole Shoe Pairing and Magnet Arc Design using Genetic Algorithm (유전자 알고리즘을 이용한 영구자석 모터의 고정자 잇날 페어링 및 자석 극호각 설계에 의한 코깅 토오크의 저감 설계)

  • Eom, Jae-Bu;Hwang, Geon-Yong;Hwang, Sang-Mun
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.51 no.1
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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.

Cogging Torque Analysis of BLDC Motor with the Axial Displacement of Rotor (축방향 변위를 가진 BLDC 전동개의 코깅토크 해석에 관한 연구)

  • Kim, Young-Kyoun;Lee, Jeong-Jong;Nam, Hyuk;Hong, Jung-Pyo;Jin, Young-Woo;Hur, Yoon
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.52 no.8
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    • pp.368-372
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    • 2003
  • This paper deals with the cogging torque analysis of a BLDC Motor, which has the axial displacement of its rotor. In order to improve the torque performance of the BLDC motor, Brushless motor is commonly designed to minimize its cogging torque. Therefore, a skewed model is used to reduce the cogging torque. However, even though the rotor or stator is skewed, the cogging torque could be increased by the axial displacement of the rotor, which occurs when the BLDC Motor is manufactured. Therefore, this paper investigates the effect of the axial displacement of the rotor on the cogging torque. In order to investigate the effect, an analysis method, which is 3D-EMCN in combination with 2D-FEM, is proposed to analyze the cogging torque of the BLDC motor with the axial displacement of its rotor, and the result of the analysis is verified by comparison with the experimental result.

Cogging Torque and Acoustic Noise Reduction in High Torque BLDC Motors by Teeth Pairings (고정자 잇날 페어링을 이용한 고출력 토크 BLDC 전동기의 코깅 토크 및 소음 저감)

  • Lee, Sang-Min;Hwang, Sang-Mun
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.48 no.3
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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.

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