• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.1
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• pp.48-56
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• 2006

This paper studies particularly applicable method for sensorless PM BLDC motor drive system. The waveform of the motor internal voltages(or back emf) contains a fundamental and higher order frequency harmonics. Therefore the third harmonic component is extracted from the stator phase voltage. The resulting third harmonic signal keeps a constant phase relationship with the rotor flux for any motor speed and load condition. Also because of low resolution of estimated signal obtained by the proposed sensorless algorithm, to improve the wide range of speed response characteristic more exactly, we propose the rotor position signal synthesizer using PLL circuit based on estimated signals. Some experimental results are provided to demonstrate the validity of the proposed control method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.7
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• pp.899-903
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• 2013

A self-bearing is an electric machine that achieves both rotational actuation and magnetic levitation using a single magnetic structure. To be able to stably levitate the rotor in a self-bearing, one needs to have an inverse of the force-current model. However, the force-current model in a self-bearing motor is typically not square. Furthermore, the elements of the matrix vary with respect to the rotational angle, resulting in singularities of the pseudo-inverse at various angles. In this paper, we propose a new force-current model that eliminates the singularities by adding a constraint in coil currents. This constraint eliminates the flux density in the stator core so that the saturation problem in the previous study is avoided. By implementing this force-current model, we are able to implement a levitation controller for a toroidally-wound self-bearing BLDC motor. The model inversion and levitation are validated experimentally.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.2
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• pp.112-118
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• 2004

Recently, development of rare earth permanent magnet with the high remanence, high coercivity allows the design of brushless motors with very high efficiency over a wide speed range. Cogging torque is produced in a permanent magnet by magnetic attraction between the rotor mounted permanent magnet and the stator teeth. It is an undesired effect that contributes to output ripple, vibration, and noise of machine. This cogging torque can be reduced by variation of magnet arc length, airgap length, magnet thickness, shifting the magnetic pole and varying the radial shoe depth and etc. In this paper, some airgap length and magnet arc that reduce cogging torque are found by finite element method(FEM) and Maxwell stress tensor method. The SPM(Surface Permanent Magnet) type of high-power Brushless DC (BLDC) motor is optimized as a sample model.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.11
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• pp.1568-1574
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• 2017

This paper studied cogging torque reduction effect for sloping notch applied two notches on stator teeth. We have confirmed accuracy of FEM(Finite Element Method) through comparison previous model using asymmetric notch for experiment and 3D FEM results, and then cogging torque comparison of previous model and sloping notch model. Also the sloping notch model has been modified to step-sloping notch model to consider manufactur. The modification method of sloping notch changed the degree of slope of notch (a)(Notch(a) sloping Deg) and the degree of Slope of notch (b)(Notch(b) Sloping Deg). When Cogging torque is case of minimum, Notch (a) Sloping Deg is $-12[^{\circ}]$ and Notch(b) Sloping Deg $12[^{\circ}]$. In this case, cogging torque was about 23.9[mNm]. Cogging torque of previous model is about 40.8[mNm], so sloping notch model is less than previous model by 41.42[%]. Also, if sloping notch model is changed to step-sloping notch model, cogging torque of step-sloping notch model is about 24.82[mNm], Therefore the difference between the two cogging torque is about 3.85[%], so step-sloping notch model can be applied when considering manufacture.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.897-899
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• 2002

BLDCM(Brushless D.C. Motor) is widely used industrial application because of high efficiency and high power density. Especially, In servo system and home appliance, BLDCM is very useful due to high control performance and low acoustic noise. In this paper, 2.5HP rated BLDCM controller and drive was developed for tread mill application. The prototype BLDCM has 4 poles rotor and 24 slots stator. Ferrite was used as a rotor magnet due to the cost and temperature characteristic. For the stable operation of tread mill, over current and high temperature can be detected by the DSP control1er. For the commutation signal, switching patterns from the sensorless circuit and hall sensor signal are used in the DSP controller.

• 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.

• Proceedings of the KIEE Conference
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• 2007.10c
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• pp.175-177
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• 2007

This paper presents for the torque characteristics and improving the efficiency of driving system of electric bicycle which applied IEWPM(Independently Excited Winding Permanent Magnet) motor. IEWPM motor can expand the number of phase from 3 phases to multiphase like SRM motor because stator windings are unconnected directly. BLDC motor raise rotor'-s electromagnetic torque per unit volume by using Spoke type permanent magnet. By using two photo sensor per phase and applying excited width, advance angle and bipolar control, we confirmed higher torque at a low speed, higher out-put at a high speed, and efficiency improvement at a wide speed control area.

• Proceedings of the KIEE Conference
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• 2004.04a
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• pp.37-39
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• 2004

This paper deals with the prediction of armature reaction field produced by 3-phase stator windings whose current waveform contains significant harmonics. On the basis of 2-d analytical technics, we derived governing equation and predicted magnetic field distribution according to rotor position. The results of predictions from the analysis are compared with corresponding FE (finite element) analyses.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.916-917
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• 2015

This paper deals with electromagneitc characteristics analysis of high-speed brushless DC motor. First, under same rated and restricted conditions, four models which have different slot combinations each other are designed using 2-d finite element (FE) analyses. Designed models are analyzed and compared in terms of core loss, copper loss, eddy-current loss, etc. On the basis of analysis results, it is found that the motor with a 2-pole PM rotor and a 6-slot stator has most outstanding performances in electromagnetic aspects.

• Proceedings of the KIEE Conference
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• 2004.10a
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• pp.60-63
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• 2004

BLDC Motor has many advantages but the motor has slots in Stator like as other conventional Motors therefore cannot be eliminated torque ripple which is not acceptable for a special purpose. For high speed and high efficiency and no torque ripple is a Double Cylinder Motor suggested which has a air-gap-winding and rotating yoke with magnet. Because Airgap winding needs no slot and no ironloss is made in rotating yoke. In this paper describes design and construction and theoretical and experimental investigation of a Double Cylinder Motor.