• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.9
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• pp.1571-1576
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• 2007

This report describes the analytical characteristic of sinewave air gap flux density for the brushless AC motor with surface permanent magnet. The analysis of sinewave air gap flux density is the key to expect the performance of back EMF for the design of brushless AC motor. The numerical analysis and FEM analysis are performed to adopt radial and parallel flux magnetization of magnet on the rotor. And it is also executed to vary the magnet arc angle and arc radius for the condition of constant and non constant air gap. This report is focused on the characteristic of sinewave air gap flux density for permanent magnet of surface brushless AC motor. This results also have more reliable data against the previous paper which had the representative numerical analysis of air gap flux density[1][2].

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.12
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• pp.2179-2189
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• 2010

This paper deals with analytical techniques for performance evaluation of small scaled wind power generator with outer permanent magnet rotor. In part (1), using transfer relations theorem, magnetic field distribution characteristics by PM and armature reaction field are derived. Moreover, electrical parameters such as back-EMF, inductance and resistance are calculated from the obtained field characteristic equations. The proposed analytical techniques are validated by nonlinear finite element method using commercial software 'Maxwell' and performance experiments of the manufactured generator. In part (2), generating characteristics analysis such as constant speed characteristics and constant resistive load characteristics, and performance evaluation according to variation of wind speed will be accomplished using the derived electrical parameters.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.731-732
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• 2008

This paper deals with design and characteristics analysis of 7.5-kW, 60,000-rpm class permanent magnet synchronous motor for turbo compressor. In order to determine the design parameters of rotor, torque per rotor volume method is applied. And, to analyze the magnetic field distribution and estimate the electrical parameters such as back EMF constant, inductance and torque constant, electromagnetic transfer relations theorem is employed. We compare the characteristics analysis results of model designed by proposed method with those by nonlinear FEA. As a result of this, the design have been validated.

• Proceedings of the KIEE Conference
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• 2005.10c
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• pp.129-131
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• 2005

This paper deals with an electromagnetic analysis and control parameter estimation of a moving-coil linear oscillatory actuator (MCLOA). Analytical solutions for electromagnetic characteristics of the MCLOA are obtained from transfer relations derived in terms of a magnetic vector potential and two-dimensional (2-d) rectangular coordinate systems. And then, on the basis of 2-d analytical solutions, control parameters such as the thrust constant, the back-emf constant and winding inductances are estimated. Finally, analytical results for both electromagnetic characteristics and control parameters of the MCLOA are validated extensively by finite element (FE) analyses. In particular, test results such as static thrust, resistance and inductance measurements are given to confirm the analyses.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1294-1296
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• 2005

Because of its cost effectiveness, the Brushless DC Motor(BLDCM) is focused by the industry these days. Considering the constant back-EMF region of the BLDCM, only a simple position information should be provided for constant torque control. From this point of view, using expensive position sensors, such as encoder, resolver, etc, decreases the cost effectiveness of the BLDCM. The Proposed detecting circuit detects position of zero crossing point(ZCP) then relative position could be calculated from ZCP. This circuit is robust to noise because of working in the current level. BLDCM is driven from the position information by the ZCP The reliability on BLDCM sensorless control using the voltage detecting circuit is shown through simulation using Matlab.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.5
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• pp.62-70
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• 2007

In this paper, the boost Power Factor Correction(PFC) technique for Direct Torque Control(DTC) of brushless DC motor drive in the constant torque region is implemented on a TMS320F2812DSP. Unlike conventional six-step PWM current control, by properly selecting the inverter voltage space vectors of the two-phase conduction mode from a simple look-up table at a predefined sampling time, the desired quasi-square wave current is obtained, therefore a much faster torque response is achieved compared to conventional current control. Furthermore, to eliminate the low-frequency torque oscillations caused by the non-ideal trapezoidal shape of the actual back-EMF waveform of the BLDC motor, a pre-stored back-EMF versus position look-up table is designed. The duty cycle of the boost converter is determined by a control algorithm based on the input voltage, output voltage which is the dc-link of the BLDC motor drive, and inductor current using average current control method with input voltage feed-forward compensation during each sampling period of the drive system. With the emergence of high-speed digital signal processors(DSPs), both PFC and simple DTC algorithms can be executed during a single sampling period of the BLDC motor drive. In the proposed method, since no PWM algorithm is required for DTC or BLDC motor drive, only one PWM output for the boost converter with 80 kHz switching frequency is used in a TMS320F2812 DSP. The validity and effectiveness of the proposed DTC of BLDC motor drive scheme with PFC are verified through the experimental results. The test results verify that the proposed PFC for DTC of BLDC motor drive improves power factor considerably from 0.77 to as close as 0.9997 with and without load conditions.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.10
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• pp.1065-1072
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• 2008

A HDD adopts a sensorless brushless DC (BLDC) motor as a spindle motor. Because there is no direct sensor measuring rotor position. open loop commutations with inductive sensing are used to increase the rotor speed up to a certain speed where the zero crossings of the back electromotive force (EMF) voltage are measurable. Therefore, successful open loop commutations are necessary for the stable start-up control of the spindle motors. In this paper, the time scale and the number of the open loop commutations are employed for design parameters to guarantee robustness to torque constant variation and initial rotor position. The design results are verified by experiments on a very low current start-up of the spindle motor with various environment. The experimental results show that the design results can decrease the start-up failure rate considerably.

• Proceedings of the KIEE Conference
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• 1991.11a
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• pp.171-174
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• 1991

Among the various PWM methods, the hysteresis-band current control PWM method is popularly used because of its simplicity of implementation, fast response characteristics and inherent peak current limiting capability. However, the current control PWM method with a fixed hysteresis-band has the disadvantage that switching frequency decreases and current ripple is high as the increasing of back-EMF. As a result, load current contains excess harmonics. This paper describes a adaptive hysteresis-bandwidth control algorithm so as to maintain the average switching frequency constant and decrease the current ripple where the hysteresis bandwidth is derived as a relation with the switching frequency. This control algorithm is applied to the surface-type brushless DC motor with separated winding and using the computer simulation, the validity of its algorithm is proved.

• Proceedings of the KIEE Conference
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• 2008.04c
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• pp.86-88
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• 2008

The rotational loss is one of the most important problems for the practical use of the high power Flywheel Energy Storage System (FESS). This rotational loss is divided as the mechanical loss by windage and bearing and iron loss by hysteresis loop and eddy current in the part of the magnetic field. So, In this paper, a double-sided PMSM/G without the iron loss is designed by analytical method of the magnetic field and estimation of the back-EMF constant represented as the design parameter. This design model consists of the double-sided PM rotor with Halbach magnetized any and coreless 3-phase winding stator. The results show that the double-sided PMSM/G without iron loss can be applicable to the high power FESS.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.53 no.4
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• pp.195-200
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• 2004

Many kinds of speed sensorless control system of induction motor had been developed. But it is difficult to implement at the real system because of complex algorithm and equations. This paper investigates a novel speed sensorless control of induction motor using neural networks. The proposed control strategy is based on neural networks using stator current and output of neural model based on state observer. The errors between the stator current and the output of neural model are back-propagated to adjust the rotor speed, so that adaptive state variable will coincide with the desired state variable. This algorithm may overcome several shortages of conventional model, such as integrator problems, small EMF at low speed and relatively large sensitivity of stator resistance variation. Also, this paper presents a newly developed optimal equation about the momentum constant and the learning rate. The proposed algorithms are verified through simulation.