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최창주,서강성,박수강,조금배,백형래,임병옥 조선대학교 에너지.자원신기술연구소 2002 에너지·자원신기술연구소 논문지 Vol.24 No.2
Single phase induction motor(SPIM) is one of the most widely used type of low power AC motors in the world, especially for domestic or commercial applications where a three phase power supply is not available. Fractional horse power single phase induction motors have no starting torque their own. So there are several ways of starting single phase induction motors. The most common type is the starting capacitor installed in series with the auxiliary winding to increase the starting torque. Also, the auxiliary winding is disconnected once the speed of the motor reaches 70 to 80% of the rated speed. In the conventional systems, this function is conducted by a centrifugal switch. But the mechanical centrifugal switch has many problems such as switch malfunction. This paper presents the new methods of universal starting switch by digital controller to overcome these shortcomings of centrifugal switch.
Battery Charge and Discharge Characterisitcs in Small Scaled Photovoltaic System
Cho, Geum-Bae,Baek, Hyung-Lae,Choi, Youn-Ok CHOSUN UNIVERSITY 1997 Basic Science and Engineering Vol.1 No.2
In any photovoltaic system, a battery storage system is needed to save some extra power and to meet the required power by load, likely, in a cloudy days or night time. Especially, for a small scale photovoltaic(PV) system in household load application, the battery storage system has a very important role for continuos power supply to household loads in night time. Even though a battery storage system help to improve the availability of solar power, the total availability of the solar power can be restricted to around 80% due to its ingerent losses involving in evergy transformation; charging and discharging chemical reactions. nowadays, the operating efficiency and performance are treated as so important factors in order to evaluate the PV system economially. This paper describes charge and discharge characteristics of a small scale PV system under controlling of a new and simple battery management system. This battery management system is composite controller having a voltage comparator, a power MOSFET switch and accessary instead of conventional relay switching devices. Experimental results show that the proposed battery management system is superior the conventional relay switching system in its the operating performance and the system reliability of the small scale PV system.
임형백 ( Hyung Baek Lim ),박지영 ( Ji Young Park ),이금옥 ( Geum Ok Lee ) 한국농촌지도학회 2009 농촌지도와 개발 Vol.16 No.1
This study empirically studies the effects of Agricultural Technology Service Center`s educational program for farmers on their incomes. The educational program for farmers has widely been managed in discourse and policy in Korea. In 2008, Agricultural Technology Service Center managed 88 educational program for farmers, where 6,409 farmers received a certificate. While there are important studies, most of them have concentrated on qualitative analysis and noneconomic effects to an educational program for farmers. This study tried to analyze whether or not there is an economic effect of an educational program for farmers, focusing on the relationship between the educational program for farmers and their income status. Multilevel models (or hierarchical linear models) were applied to this study. Multilevel model is a quantitative model of parameters that vary at more than one level and show hierarchical structures between levels. This study particularly accentuates that an educational program for farmers is more meaningful when it can raise farmers` incomes by region and by educational program for farmers.