• Journal of Advanced Marine Engineering and Technology
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• v.34 no.2
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• pp.282-288
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• 2010

The paper presents the characteristics of capacity control of variable speed water cooler with the electronic expansion valve open/close degree. It is a preliminary study on the optimum control of the water cooler system using a variable speed compressor controlled by inverter. The electronic expansion valve controlled by the variation of compressor speed maintains the constant degree of superheat at the evaporator outlet, which aims to find the degree of superheat obtaining the optimum refrigeration effect. The investigation indicates that there is a point achieving the maximum cooling capacity by the variation of the electronic expansion valve open/close degree with constant compressor speed.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.316-317
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• 2010

본 논문은 압축기용 영구자석 동기전동기의 효율 개선을 위한 새로운 운전 제어 방법에 대해 제안한다, 일반적으로 냉장고용 압축기는 종래에 고정속도로 운전되는 유도기를 많이 적용해 왔으나 최근 고효율화, 고성능화의 요구증대로 영구자석 동기전동기를 적용하여 가변속 제어가 가능하도록 구성한다. 최근 냉장고의 경우 대용량화 고효율화의 요구로 인해 더 넓은 운전 범위 운전 특성이 요구되고 있는 실정이다. 이에 따라 본 논문에서 제안하는 제어 방법은 넓은 운전 제어 및 고효율 운전이 가능하도록 운전 속도에 따라 구형파 제어 및 정현파 제어가 전환이 되어 속도 및 부하조건에 따라 최적 제어가 이루어지는 방법을 제안한다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.5
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• pp.466-466
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• 2000

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.6
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• pp.1122-1127
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• 2001

This paper proposed a speed adaptive control system with load torque observer and feed-forward compensation using neural network for air compressor system driven an induction motor. The motor receive impact load change under the influence of piston movement of up and down, and so it difficult to obtain good speed control characteristics. With real-time adjusting control gain estimated in neural network, control characteristics of motor is improved. The validity of the proposed system is confirmed through the theoretical analysis and computer simulation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.397-400
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• 2001

This paper proposed a speed adaptive control system with load torque observer and feed-forward compensation using neural network for air compressor system driven an induction motor. The motor receive impact load change under the influence of piston movement of up and down, and so it difficult to obtain good speed control characteristics. With real-time adjusting control gain estimated in neural network, control characteristics of motor is improved. The validity of the proposed system is confirmed through the theoretical analysis and computer simulation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.12
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• pp.502-508
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• 2016

An optimized PI controller design method is presented to promote the control performance of an oil cooler system for high precision machine tools. First, a transfer function model of the oil cooler system with a variable rotating speed compressor was obtained by the perturbation method as the first order system with a negligible dead time. Then, the closed-loop control system was described as the second order system with a zero. Its dynamic behaviors are mostly governed by characteristic parameters, the damping ratio, and the natural frequency which is incorporated in PI gains. Next, an optimum integral of the time-weighted absolute error (ITAE) criterion was applied to the second order system. The characteristic parameters can be determined by the given design specifications, percent overshoots and settling times and comparisons with the ITAE criterion. Hence, the PI gains were plainly identified in a deterministic way. Finally, the PI gains were fine-tuned to obtain desirable dynamics in real systems, considering the zero effect and parameter variations. The validity of the proposed method was proven by computer simulations and real experiments for selected cases.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.120-120
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• 2010

에너지 절약적 차원에서 한 대의 실외기에 다수의 실내기가 접속되는 개별공조형 멀티 열펌프에 관한 연구 및 개발과 보급이 증대되고 있다. 본 연구에서는 복수의 실내기를 갖고 가변속 압축기를 채용한 지열원 물대공기 멀티열펌프시스템을 학교 현장에 설치하여 제조사의 운전 제어 알고리즘에 따라 일일 냉난방 실증 성능 특성을 분석하였다. 2008년 9월 30일의 냉방부하가 낮은 일자에 대하여 시간에 따른 부하 변동에 따라 압축기의 용량가변으로 실내기 냉방용량은 정격용량 대비 17.1%에서 111.3%의 범위에서 변이되었으나, 열펌프 유닛의 일일 최대 COP는 6.2를 나타냈으며, 일일 평균 열펌프 유닛 COP는 4.5로 열펌프 유닛 인증 기준 이상의 성능을 나타냈다. 2008년 11월 10일 대비 2008년 12월 15일에는 시스템 가동 중의 평균 외기온도가 $9.6^{\circ}C$ 감소하였으나, 각 재실공간의 용도별 부분 부하특성으로 11월 10일 보다 난방 부하량이 작게 나타났다. 하지만, 12월 15일에는 부하량이 매우 작아서 11월 10일보다 잦은 압축기 가변에 따른 손실로 일일 평균 COP가 낮게 나타났다. 2009년 1월 12일에는 정격 용량대비 94%의 부하율로 11월 10일과 12월 15일 대비 4배 이상의 부하량으로 압축기 용량 가변율이 작아서 난방용량과 COP 변화율이 작게 나타났다. 2009년 1월 12일에는 지중순환수의 실외열교환기 유입온도가 2008년 12월 15일보다 감소하고, 시스템의 난방용량 증가로 상대적으로 응축기와 증발기 크기가 감소한 효과로 히트펌프 유닛 COP가 감소하였으나, 본 지열원 열펌프 제조사에서 생산하고 있는 본 지열원 시스템과 동일한 압축기 등을 채용한 동일 용량의 공기열원 열펌프의 1월 12일 외기온도 $-10^{\circ}C$에서의 열펌프 유닛 COP 대비 70% 우수한 성능을 나타냈다. 본 지열원 히트펌프의 2008년 11월 10일의 일일 평균 히트펌프 유닛 COP는 외기온도가 낮고 일일 부하량이 크게 나타난 1월 12일의 일일 평균 히트펌프 유닛 COP 대비 37% 높게 나타났으나, 지중순환펌프의 정속운전으로 시스템 요구 지중순환수 유량 증가에 따른 성능 향상보다 소비전력 증가 영향이 커서 1월 12일의 시스템 COP 보다 33.3% 작은 값을 나타냈다. 본 연구의 용량 가변형 압축기를 채용한 지열원 멀티 히트펌프 유닛을 지열원 냉난방 시스템의 히트펌프 유닛으로 사용할 경우 시스템 최적화를 통한 시스템 COP 향상과 연간에너지 절감을 이루기 위해서는 히트펌프의 용량 변화 시에 지중순환펌프의 순환 유량 최적화를 위한 효율적 운전 제어 알고리즘 개발이 요구된다.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.2
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• pp.238-243
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• 2011

The ambient temperature of the experimental conditions changes by varying the speed of the compressor and the electronic expansion valve opening. The effects of changing valve opening to the entire system has been investigated. The results show that the ambient temperatures of $35^{\circ}C$ and $30^{\circ}C$ controlled at 30Hz must be avoided. The capacity control range of the control compressor with changing speed is about 43~100% at $35^{\circ}C$, 43~100% at $25^{\circ}C$ and 48~100% at $10^{\circ}C$, respectively. The results show the capacity control range decreases with decreasing ambient temperature.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.1
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• pp.1-8
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• 2012

Recently, the needs of system performances such as working speed and processing accuracy in machine tools have been increased. Especially, the speed increment generates harmful heat at both moving part of the machine tools and handicrafts. The heat is a main drawback to progress accuracy of the processing. Hence, a cooler system to control temperature is inevitable for the machine tools. In general, two representative control schemes, hot-gas bypass and variable speed control of a compressor, have been adopted in the water cooler system. In this paper, comparisons of system performances according to the control schemes in a cooler for machine tools were conducted in detail. Each proportional-integral feedback controller for the two different control systems is designed. The system performances, especially the temperature control accuracy and coefficient of performance which is a criterion of energy saving, were mainly analyzed through various experiments using 1RT water cooler system with different two types of control scheme. These evaluations will provide useful information to choose suitable water cooler system for the engineers who design controllers of the cooler system for machine tools.

• Journal of the Institute of Convergence Signal Processing
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• v.14 no.2
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• pp.130-135
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• 2013

Recently, the needs of system performances such as working speed and processing accuracy in machine tools have been increased. Especially, the working speed increment generates harmful heat at both moving part of the machine tools and handicrafts. The heat is a main drawback to progress accuracy of the processing. Hence, a oil cooler to control temperature is inevitable for the machine tools. In general, two representative control schemes, hot-gas bypass and variable speed control of a compressor, have been adopted in the oil cooler system. In this paper, the compressor's speed are controlled to keep reference value of temperature at oil outlet. The precision processing of a machine tool is required for an oil cooler guaranteeing ${\pm}0.1^{\circ}C$ temperature control. But the oil cooler with precision temperature control is expensive. Therefore in this paper, instead of a on/off(relay) control method, a PID and phase angle electric power control method is proposed for the precision control of an oil cooler. The proposed controller is implemented and tested at the temperature of $23^{\circ}C$, $24^{\circ}C$ and $25^{\circ}C$.