• The Korean Journal of Rheology
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• v.3 no.1
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• pp.76-85
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• 1991

적은양의 분자량이 큰선형 고부자를 수용액에 첨가함으로서 얻어지는 마찰저항가소 연구가 rotating disk 장치를 이용해 수행되었다. 마찰저항 감소제로 poly(ethylene oxide)와 poly(acrylamide)를 사용하였으며 고분자 분자량 고분자 농도, disk 의 회전속도 및 온도 등 여러 가지 인자에 대한 마찰정항감소의 의존성을 연구하였다. 또한 마찰저항 감소 효과와 고분자 용액의 점도평균 분자량을 동시에 측정함으로서 고분자 퇴화에 대한 연구도 수행하 였다. 마찰저항감소는 고분자 농도가 증가함에 따라 임계농도에 도달할때까지 증가하였고 낮은 농도에서는 분자량이 큰 고분자일수록 더욱 큰 마찰저항 감소효과를 나타내었다. 마찰 감소 진행 중의 높은 전단력에 기인하는 고분자의 분해는 고분자 농도가 낮은데에서 더욱두 드러지게 나타났으며 온도 효과의 연구로부터 poly(acrylamide)가 poly(ethylene oxide)보다 열적으로 안정함을 알수 있었다.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.2
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• pp.101-109
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• 2005

The newly developed speed sensorless control scheme is proposed to estimate both motor speed and rotor resistance simultaneously using variable rotor flux. The rotor flux is given as sinusoidal waveform with an amplitude and a frequency without affecting precise torque control. Especially the proposed method makes the simultaneous estimation of rotor resistance and speed with high precision even though at the low speed area including a few rpm. Moreover, on-line identification of rotor resistance can be performed simply without calculating troublesome trigonometric functions and complicated integral computation. Therefore, the proposed system can be accomplished by using very cheap microprocessors for several applications. The results of the numerical simulations and experiments demonstrate that this method is effective to estimate the speed and on-line identification of rotor resistance for sensorless induction motors.

• Journal of Sensor Science and Technology
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• v.2 no.1
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• pp.65-74
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• 1993

A miniature size electrostatic induction motor has been fabricated and studied with emphasis on the role of the surface resistivity, the relative dielectric constant and the charge relaxation time constant of the rotor surface materials and the rotor liner materials, which, however, control the surface charge induction and relaxation on the rotor material surface and the field intensity between the rotor and the stator of the motor. It is found that the surface resistivity and/or the relative dielectric constant, and the charge relaxation time constant of the rotor surface material enfluenced significantly to motor speed controlled by the surface charge induction and relaxation on the rotor surface depending on the applied voltage and/or frequency changing. The resistivity of the rotor liner material is also found to be effected to the motor speed greatly by control of the field intensity between the rotor and the stator and of the surface charge distribution of the induced charge on the rotor. As a result, a maximum no load rotor speed of the motor tested was about 5500 rpm at the applied voltage of 4.5 kV and the frequency of 220 Hz for the case of the rotor surface material of $BaTiO_{3}$ 80% in the resin binder layered on the copper-foil rotor liner material.

• Journal of the Korean Magnetics Society
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• v.26 no.2
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• pp.67-69
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• 2016

Recently, cost of rare-earth magnets has been raised, because rare-earth magnets are monopolized and the export is also regulated in China. For this reason, the induction motor is operated without the rare-earth magnets. The efficient development of induction motor is more important for economical scheme. A torque of the induction motor is computed and the correlation between dimension and resistance of the squirrel cage rotor is investigated. Also, the correlation between leakage reactance and torque was analyzed with respect to the same dimension of rotor with different shapes. Therefore, this paper proposes the method of improvement for squirrel cage rotor.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.6
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• pp.517-523
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• 2002

A sensorless control of a PM synchronous motor with the compensation of the motor parameter variation is presented. The rotor position is estimated by using the d-axis and q-axis current errors between the real system and motor model of the position estimator. The stator resistance is measured at low speeds when the motor changes its rotating direction and the variation of the stator resistance and back emf constant caused by the temperature variation is compensated. The gains in the position estimator are also adapted according to the motor speeds.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.10 no.2
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• pp.71-77
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• 1996

The end-ring may contribute a significant influence to the performance of machine. The induced currents flow through the bars of a cage rotor and complete their closed paths by passing around the end-ring. This dissertation is to describe a method for calculating end-ring resistance of squirrel cage rotor, based on 3-D finite element method(A-$\Phi$). The resistance under consideration of skin effect is calculated by using Joule's loss equation.

• Journal of the Korean Magnetics Society
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• v.6 no.5
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• pp.287-293
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• 1996

The squirrel cage rotors of induction motors may have several faults such as broken bars, bad spots in end ring and abnormal skew caused by improper processing. These faults may cause bad effects on the performance of the induction motor. This paper proposes the detecting technique of these faults by analyzing the induced current of the detecting electric magnet, using 2-D finite element method taking account of the rotor movement.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.65-66
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• 2007

본 논문은 파라미터 변동에 잘 적응하며 강인한 영구자석 동기전동기의 위치센서 없는 센서리스 제어를 위해 개선된 슬라이딩 모드 관측기에 고정자 저항 추정기능을 추가한 새로운 슬라이딩 모드 적응 관측기를 제안한다. 제안된 관측기는 개선된 슬라이딩 모드 관측기를 사용함으로써 기존의 슬라이딩 모드 관측기에서 채터링(Chattering) 문제 해결을 위해 저역통과필터(Low-pass filter)의 사용 및 추가적인 회전자의 위치보상은 Sigmoid 함수를 스위칭 함수로 사용하므로 제거 할 수가 있다. 또한 고정자 저항 추정기능을 추가하여 센서리스 운행 중 환경적 요인으로 인한 고정자 저항값의 변동이나 초기에 고정자 저항값을 잘못 알고 있더라도 빠른 적응을 통해서 추정오차를 절감시켜 전동기의 속도추정 성능을 향상시킬수 있다. 또한 기존의 적응 슬라이딩 모드 관측기에서의 적분연산을 줄임으로써 제어시스템의 성능을 개선시켰다 제안된 관측기의 안정성은 Lyapunov 후보 함수를 이용하여 관측기의 이득을 설정함으로써 검증하였으며 관측기의 성능은 시뮬레이션을 통한 실험을 통하여 그 타당성을 입증하였다.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.10-11
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• 2011

단일 회전자 전동기와 달리 동일한 크기에서 높은 출력 밀도와 높은 토크의 장점이 있는 이중 회전자 구조를 갖는 전동기는 공간적 제약을 받는 전기 자동차, 전기 이륜차 등의 분야에 활발히 연구되고 있다. 이중 회전자 구조를 갖는 전동기는 고 토크 운전을 위해 이중 인버터 운전 방식이 요구된다. 이때, 내부와 외부전동기의 역기전력이 다를 때 이를 고려하지 않고 운전한다면 발생하는 동손이 증가하여 운전효율 저하로 이어진다. 본 논문에서는 이중 회전자 구조를 갖는 3상 BLDC 전동기에서 내부와 외부전동기의 역기전력비(${\alpha}$)와 고정자 저항 비(${\beta}$)를 고려한 전류분배방식을 통해 동손을 최소화하는 최적운전 알고리즘을 제안하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.808-811
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• 2002

The stability for a speed sensorless vector control of an induction machine has been studied. These studies show that the sensorless control is apt to be more unstable than the control with sensor on the variation for stator resistance, rotor resistance and system parameters of the machine. First, this paper investigates the speed characteristics when the inertia, J, changes and the rotor resistance, R$_{r}$ changes respectively for a step change of a speed reference, $\omega$. Then, the new speed estimation algorithms with no effects on the parameters variation of the machine and the system is proposed. The proposed method is to implement the observer using voltage, current and constant of the machine. The results are verified by simulation.