• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.36 no.12
• /
• pp.874-887
• /
• 1987

The efficiency of a synchronous motor can be substantially improved by controlling armature voltage, field excitation, and load angle on optimum values which yield minimum input power at any specified torque and speed. This improvement is particularly noticeable in the case of light loads. In addition, the control of armature input voltage improves the power factor at which the motor operates. Employed in the analysis is a new equivalent circuit model of the motor which incorporates the frequency dependent nature of the motor parameters and the effects of iron loss. The stability of synchronous motor operation is studied by applying the Nyquist stability criterion to the linearized equations which describe the behavior of the motor as the motor loads perturb about a steady-state operating point. This investigation reveals that, in some cases, the stable region of the motor is delineated from the results of a computer simulation. With a view to reducing harmonic loss and improving torque pulsation from harmonic components, a very poweful pulse amplitude modulation (PAM) method using an 16-bit microcomputer has been developed. This method has the advantages of simplicity of control algorithms and requires small memory space for storing thyristor trigger angles for a three-phase PAM inverter. The method can be used for smooth control of both modulation depth and frequency over a wide range.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.61 no.4
• /
• pp.206-213
• /
• 2012

This paper propose a improved speed control system for five-phase squirrel-cage induction motor(IM) considering effects of 3rd. harmonic current components with field oriented control(FOC) A five-phase IM drives present unique characteristics due to the additional degrees of freedom and also drives possess many others advantage compared with the traditional three-phase motor drive system, such as reducing a amplitude of torque pulsation at low frequency and increasing the reliability. In order to maximize the torque per ampere, the proposed motor has concentrated windings. The produced back-electromotive force is almost trapezoidal, and the motor is supplied with the combined sinusoidal plus third harmonic of currents. There is necessary to controlled 3rd harmonic current. For presenting the superior performance of the proposed the speed control system, experimental results are presented using a 32-bit fixed point TMS320F2812 DSP with 1.5[KW] induction motor.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.12 no.4
• /
• pp.277-284
• /
• 2007

This paper describes independent phase BLDC motor with a maximum torque among BLDC motor used for electric propulsion system Independent phase BLDC motor has characteristic that phases of stator we independent electrically. This paper is modeling two type of 3 phases BLDC motors, one has Y-connection type and the other has independent type, and it shows simulation of them, compares its characteristics. As a result of simulation, phase voltage of independent 3 phase BLDC motor is higher than Y-connection three phase BLDC motor. When the stator resistance and inductance are stable, high phase voltage causes an increase in maximum phase current and an increases in it serially causes an increase of maximum torque. It is also found that the current pulsation of independent phase BLDC motor was decreased by controlling phase current of independent BLDC motor.

• Proceedings of the KIEE Conference
• /
• 2007.07a
• /
• pp.983-984
• /
• 2007

The spindle motor used on the ODD has a characteristic that electromagnetic pulsation and noise change differently by magnetization pattern of rotor. Therefore, design of magnetizer yoke that make to have optimal magnetization pattern is very important. In this paper, we proposed an analysis method that applies magnetizer analysis result to the spindle motor. We measured back-EMF of the real spindle motor. And then, we verified validity of the proposed analysis method by comparing the measurement and analysis result. Also, we designed the magnetizer shape that has optimal magnetization pattern by using proposed method. As a result, we reduced cogging torque of the spindle motor.

• Journal of Ocean Engineering and Technology
• /
• v.27 no.3
• /
• pp.67-72
• /
• 2013

In this study, numerical analyses that considered the dynamic interaction effects between the flow and a turbine were carried out to investigate the power output performance of an H-type Darrieus turbine rotor, which is one of the representative lifting-type vertical-axis tidal-current turbines. For this purpose, a commercial CFD code, Star-CCM+, was utilized for an example three-bladed turbine with a rotor diameter of 3.5 m, a solidity of 0.13, and the blade shape of an NACA0020 airfoil, and the optimal tip speed ratio (TSR) and corresponding maximum power coefficient were evaluated through exhaustive simulations with different sets of flow speed and external torque conditions. The optimal TSR and maximum power coefficient were found to be approximately 1.84 and 48%, respectively. The torque and angular velocity pulsations were also investigated, and it was found that the pulsation ratios for the torque and angular velocity were gradually increased and decreased with an increase in TSR, respectively.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.26 no.11
• /
• pp.87-96
• /
• 2012

This paper propose a development of surface permanent mount synchronous generator(SPMSG) for 5-phase 5Kw in order to study a polyphase ac machinery that keep hold of advantages more than traditional three-phase squirrel-cage induction motor, such as reducing a amplitude of torque pulsation decreasing electric noises, and increasing the reliability. Design methods of the generator use a development tools with Maxwell 2D and Simplorer. There are designed drawing of manufactured frames of the SPMSG. A amplitude and waveform of the generated electromotive force, FFT analysis of harmonics within output voltages, and reviewing a experiment results are shown by variable output frequency. We are presenting a design and manufacture methods for the SPMSG.

• Proceedings of the KIEE Conference
• /
• 1992.07b
• /
• pp.1088-1091
• /
• 1992

Programmed PWM(Pulse Width Modulated) generation techniques eliminating several low order harmonics have been widely used in the inverter circuit which produces minimum current ripple, reduced torque pulsation and thereby improves overall system performance. However, the applications of the programmed PWM technique are limited to CVCF(Constant Voltage Constant Frequency) applications and various motor drives. Although the programmed PWM produces a lower harmonic distorted waveform than the carrier modulated PWM, real-time programming is not possible because of the complicated calculation required for the gating signal. In this paper, a new programmed PWM technique named TAM (time averaging model) is developed to compensate for the demerits of the conventional programmed PWM technique with moderate harmonic distortion. Computer simulations are performed to verify the performance of the proposed algorithm.

• Proceedings of the KIPE Conference
• /
• 2002.07a
• /
• pp.104-109
• /
• 2002

본 논문에서는 기존의 BLDC전동기 구동방식에 의한 등가회로를 스위치가 off되는 상의 전류 및 역기전력을 고려한 새로운 토크모델을 이용하여 사다리꼴 역기전력을 가지는 BLDC전동기의 전환시 발생하는 토크맥동과 평균토크를 개선할 수 있는 새로운 토크맥동 저감방식을 제안하였다. BLDC전동기의 전기적인 등가모델 및 전류현상과 전환시 발생하는 토크맥동에 대하여 기술하였으며 발생토크의 변동의 원인이 되는 역기전력과 전류와의 관계를 고찰하였다. 이를 바탕으로 전환시 발생하는 토크맥동을 개선하기 위하여 스위칭 소자가 off 되는 상의 전류 및 역기전력을 고려한 상승상과 감쇄상의 전류기울기 제어 및 전환시점제어를 통한 토크맥동 저감방식을 제안하였으며, 전환시 발생하는 맥동토크의 저감효과에 대하여 해석하였다. 이의 검증을 위하여 MATLAB/Simulink를 이용하여 제안한 토크맥동 저감방식의 저감효과의 타당성을 검증하였다.

• Proceedings of the KIPE Conference
• /
• 1998.10a
• /
• pp.493-497
• /
• 1998

In this paper, a three phase voltage source inverter synchronous motor drive is introduced which is capable of producing an approximate to sine-wave currents in the stator windings. Compare to a conventional current forced synchronous machine drive, for the same machine loss, a gain in out put per unit overall volume of 125% at a 50Hz supply frequency has been achieved. In addition, the torque pulsation has been drastically reduced. These improvements are achieved by introducing new rotor windings which are capable of controlling the stator current waveforms an approximate to sine-wave. A computer program has been developed which can be used to predict the dynamic performance of this drive/system. The paper describes the design of rotor windings for cylindrical rotor motor but the theory is equally applicable to salient-pole designs.

• Proceedings of the KIEE Conference
• /
• 1988.07a
• /
• pp.127-129
• /
• 1988

Square-wave current source inverter drives suffer from torque pulsation and speed variation at low speed. Attempts to minimize these problems, CSI PWM strategies have been reported. It is shown that these PWM strategies are based on unnecessarily restrictive modulation laws. In this paper, trapezoidal PWM strategy for CSI is investigated theoratically by double fourier series and we proposed Harmonic Speed ripple Factor(HSF) that is independent of motor parameters and load conditions. Speed ripple are considered in T-PWM and square wave inverter by HSF. We obtain modulation index(M) and carrier ratio (CR) for minimum speed ripple.