• 전기학회논문지
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• 제66권11호
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• pp.1584-1590
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• 2017

This paper presents a implementation method of reliable speed limitation controller considering motor parameter variation in high speed operation. In spinning process of drum washing machine, speed increase has to be limited when unallowable imbalance mass is detected. Otherwise, severe noise and vibration can happen because noise and vibration are proportional to imbalance mass. To detect imbalance mass, d-axis current magnitude is used. However, we have to compensate for back-emf and power supply variation by means of detecting them because d-axis current is affected by both of them. On the other hand, we have to carefully estimate back-emf because back-emf is affected by stator resistance variation and inverter voltage error. Stator resistance variation can happen by manufacturing process for mass production or temperature variation in running. And there are inverter voltage errors between command voltage from micro-computer to inverter and real voltage from inverter to motor because of rising and falling time delay and turn-on resistance of power semiconductor switch. To solve this problem, we propose 2-step align current injection method which is to inject step-wise current right before starting. By this method, we can simply obtain stator resistance by ratio of voltage without inverter voltage error and current, and we can measure inverter voltage error. So we can obtain more exact model current, and then by simple calculation with compensation gain, we can estimate more accurate motor back-emf. We show that this method works well. It is verified through experiments.

• 설비공학논문집
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• 제13권5호
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• pp.348-355
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• 2001

The coupled conduction and convection heat transfer from a protruding heated module in a horizontal channel with a variation of channel height is experimentally investigated. The input power to the module is 3, 7W and thermal resistance of module support is 0.06 , 1.03 and 158K/W. the Reynolds number ranged from 350 to 4500 corresponding to the inlet velocity(0.4~1.3 m/s) and channel height(11~35 mm). The results were obtained that the decrease of thermal resistance of module support reduces the module temperature by redistributing the heat flux and the overall thermal resistance of the module. In the study the effect of channel height is very significant in the adiabatic condition, but negligible in the conjugate condition. Finally, correlations for Nusselt number and $Q_B$/Q with a variation of Reynolds number were developed respectively.

• JSTS:Journal of Semiconductor Technology and Science
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• 제17권3호
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• pp.458-464
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• 2017

A magnetic tunnel junction (MTJ) based ternary content addressable memory (TCAM) is proposed which provides non-volatility. A unit cell of the TCAM has two MTJ's and 4.875 transistors, which allows the realization of TCAM in a small area. The equivalent resistance of parallel connected multiple unit cells is compared with the equivalent resistance of parallel connected multiple reference resistance, which provides the averaging effect of the variations of device characteristics. This averaging effect renders the proposed TCAM to be variation-tolerant. Using 65-nm CMOS model parameters, the operation of the proposed TCAM has been evaluated including the Monte-Carlo simulated variations of the device characteristics, the supply voltage variation, and the temperature variation. With the tunneling magnetoresistance ratio (TMR) of 1.5 and all the variations being included, the error probability of the search operation is found to be smaller than 0.033-%.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.412-414
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• 1996

The rotor resistance variation has a large effect on the field oriented control system of induction machine. In this paper, the adaptation technique based on MRAC is used to identify the rotor resistance variation. The criterion function used in the adaptation algorithm is the error function of the two reactive powers of the induction motor. The one is obtained from the voltages and the currents of the stator of the induction motor. And the other is estimated from the rotor flux and stator current. We simulated this control system operated by field oriented control and assured the robustness of the induction motor control system against the rotor resistence variation.

• Journal of Biosystems Engineering
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• 제4권2호
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• pp.53-63
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• 1979

The knowlege of thermal properties of rough rice has become of greate importance to the analysis of heat and mass transfer phenomenon in rice drying and storage process. Some information is available on the thermal properties of rough rice in foreign countries but is not available for these properties in Korea. A fundamental study was made to determine the thermal conductivity and thermal diffusivity of rough rice with line source method and to select current and resistance suitable for these properties from investigating the effect of current and resistance of heating wire on the temperature rise. The result of this study may be summarized as follows ; 1. Even through the power per unit length of heating wires is about the same, the tendency of temperature rise showed a little difference among them , and the suitable range of it for thermal properties was found to be 3.56-5.37w/m. 2. the most desirable resistance and current of heating wire was 18.40 ohm/m, 0.44 amperes among three kinds of heating wires and currents, respectively. because it took 13 minutes or so for the heating wire to reach equilibrium temperature. 3. The thermal conductivity of rough rice was 0.120-0.130 w/m$ ^\circ C$. and thermal diffusivity of it was $5.8210 $\times10^{-8} -9.7529 $\times10^{-8} m^2 /s.$ 4.The thermal conductivity showed a little difference in variation with resistance of heating wire but the variation of current of heating wire at the same resistance did not affect the thermal conductivity , and the thermal diffusivity was not affected by the variation of resistance and current.

• 조명전기설비학회논문지
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• 제19권3호
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• pp.51-56
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• 2005

접지의 성능을 결정하는 기본 요소인 접지저항을 측정하는 것은 성능평가를 위한 중요한 기술이 된다. 접지저항의 정확한 측정을 위하여는 측정 환경상 고려하여야 할 주요한 변수들이 있는데 실제의 측정 현장에서 이러한 변수들을 알고 측정하기는 곤란한 것이 현실이다. 본 논문에서는 3점전위강하법상의 전류전극에 이르기까지 나타나는 전위차 특성 곡선에 대하여 측정 환경 변수의 특성을 내포하고 있는 변이율이라는 개념을 도입하여 미지의 측정 환경 변수중에서도 가능한 접지저항의 참값에 근접한 측정을 지향하는 방법을 제의한 것이다. 이 이론은 이미 기검증된 논문들의 결과 내용을 분석함으로써 귀납적인 결론을 유도한 것이다.

• Journal of Advanced Marine Engineering and Technology
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• 제31권8호
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• pp.1013-1019
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• 2007

This paper is about structural analysis of globe valve for controlling cryogenic LNG's flow or stop in normal temperature. The used valve is demanded safety resistance for inner pressure and temperature variation caused by using it in cryogenic, high pressure surrounding. This study evaluates for safety resistance for inner pressure and temperature variation by heat transfer analysis in cryogenic surrounding, heat stress analysis in temperature variation and deformation analysis in high pressure.

• Journal of Power Electronics
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• 제9권3호
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• pp.354-364
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• 2009

Rotor resistance variation due to changing rotor temperature is a significant issue in the design of induction motor controls. In this work, a new on-line rotor resistance estimator is proposed based on an alternate qd induction machine model which provides better mathematical representation of an induction machine than the classical qd model (which uses constant parameters). This is because the former simultaneously includes leakage saturation, magnetizing path saturation, and distributed circuit effects in the rotor conductors. The comparisons via computer simulation studies show the ability of the proposed estimator to accurately track rotor resistance variation. For the experimental studies, due to the difficulty in measuring the actual rotor resistance, comparison of the controller performance using the proposed estimator, the classical qd model based estimator, and no estimator is made.

• International Journal of Precision Engineering and Manufacturing
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• 제5권3호
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• pp.5-10
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• 2004

Electric contacts serve the purpose of transmitting electric signals across two conducting components. In this paper, the effects of contact conditions such as surface roughness, oxidation, and contamination were investigated with respect to electrical resistance variation of a connector in a direct current circuit. Such change in the electrical resistance is particularly important for low power circuits. The experimental results showed that compared with the effects of contact surface scratch or oxidation, the effect of contamination on the resistance variation was the most significant. In order to minimize failure due to electrical resistance change at the contact region, proper sealing to prevent contamination from entering the interface is needed.

• 대한조선학회논문집
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• 제46권5호
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• pp.471-478
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• 2009

The present paper deals with characteristics of resistance performance according to the variation of synthetic ice thickness and hull form. The resistance test has been conducted with pack ice condition in Pusan National University towing tank. Stem angle has been chosen as main parameters for the variation of hull form characteristics, which is the most important factor especially in icebreaking cargo vessel. The serial comparisons of resistance test have been done with the variation of hull form parameter as well as with the different thickness of synthetic ice. The different trend of resistance performances with increasing of stem angle has been shown at each synthetic ice thickness. The present test results is expected to be confirmed by comparing the test results in ice tank in the near future.