• Title/Summary/Keyword: Bypass-circuit

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An Experimental Study on the Performance Characteristics of a Single-Circuit Multi Cycle and a Bypass Two-Circuit Multi Cycle (단일유로 멀티사이클 및 바이패스유로 멀티사이클 적용 냉동시스템의 성능특성에 관한 실험적 연구)

  • Song, Young-Seung;Jung, Hae-Won;Yoon, Won-Jae;Kim, Yong-Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.23 no.7
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    • pp.513-519
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    • 2011
  • The object of this study is to investigate the performance characteristics of refrigerators using a single-circuit multi cycle and a bypass two-circuit multi cycle. Each refrigeration cycle was tested by varying secondary fluid mass flow rate and temperature. Based on the experimental data, the optimum refrigerant charge was 48 g and the COP at the optimum secondary fluid mass flow rate was 1.53 for the single-circuit multi cycle. For freezer(F)-only mode, both the single-circuit multi cycle and the bypass two-circuit multi cycle were operated at overcharge conditions, resulting in an increase of the secondary fluid mass flow rate. The maximum COPs of the single-circuit multi cycle and the bypass two-circuit multi cycle were 1.22 and 1.35, respectively. The COP increased by 10.7% with the application of the bypass two-circuit multi cycle.

Performance Characteristics of a Bypass Two-Circuit Refrigeration System (바이패스유로 멀티사이클을 적용한 냉동시스템의 성능특성에 관한 연구)

  • Kim, Ki-Youl;Jung, Hae-Won;Kim, Yong-Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.21 no.6
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    • pp.319-325
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    • 2009
  • The purpose of this study is to investigate the performance characteristics of a bypass two-circuit refrigerator. A bench scale refrigeration system was designed and constructed to estimate possible performance improvement of the bypass two-circuit refrigerator. The experiments were conducted in the bench scale refrigeration system by varying capacity of the condenser and refrigerant charge amount with an adoption of a refrigerant storage vessel. The COPs of the bypass two-circuit refrigeration system in the refrigerator and freezer (RF)-mode and freezer(F) only-mode were increased by 10% and 17%, respectively, with increasing the capacity of the condenser. Besides, the COP of the system in the F only-mode was increased by 10% by adopting the refrigerant storage vessel.

Design Technique Using Bypass Capacitor to Improve Antenna Efficiency of Inverted-F Antenna with Band Stop Matching Circuit (Band Stop Matching Circuit이 적용된 Inverted-F Antenna의 Bypass Capacitor를 이용한 안테나 효율 향상 기법)

  • Bae, Jang Hwan;Choi, Woo Cheol;Lim, Seonho;Yoon, Young Joong
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.30 no.1
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    • pp.1-7
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    • 2019
  • In this paper, a design technique using a bypass capacitor is proposed to improve the antenna efficiency of an inverted-F antenna (IFA) with a band stop matching circuit (BSMC). The proposed antenna operates in the LTE bands 26 and 5(814~ 894 MHz). The bandwidth of the IFA is expanded from 803~863 MHz to 800~888 MHz using the impedance change caused by the BSMC. To enhance the antenna efficiency in the expanded frequency band, the bypass capacitor is applied to the IFA with the BSMC. The bypass capacitor improves the efficiency of the antenna by reducing the current variation of the IFA with the BSMC. The proposed antenna has a bandwidth of 804~895 MHz and the antenna efficiency increases by more than 10 % in the extended frequency band by using the bypass capacitor.

Comparison Analysis of Dynamic Characteristics of Servo-hydraulic Piezo-driven Injector between 3-way and Bypass-circuit Type (3-way형과 Bypass형 서보유압 피에조 인젝터의 구동특성 비교)

  • Jo, Insu;Jeong, Myoungchul;Lee, Jinwook
    • Transactions of the Korean Society of Automotive Engineers
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    • v.21 no.5
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    • pp.169-175
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    • 2013
  • CRDi technology of diesel engine was developed from in the early 2000s due to a need to increase fuel efficiency and environment care. Especially, high-pressure fuel injection system in CRDi system which has a fuel injection unit including an injector, a fuel pump and common-rail, etc. becomes possible to make the exhaust gas clean as well as power improvement. In this study, comparison of dynamic characteristics of servo-hydraulic piezo-driven injector with 3-way and bypass-circuit type was analyzed by using the AMESim code. As results of this study, it found the bypass-circuit inside servo-hydraulic piezo injector can cause a faster injection response than that of the 3-way type. Also it was shown that bypass-circuit type had better control capability due to hydraulic bypass system.

The Improvement of Junction Box Within Photovoltaic Power System

  • Sun, Ki-Ju;Cheon, Min-Woo
    • Transactions on Electrical and Electronic Materials
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    • v.17 no.6
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    • pp.359-362
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    • 2016
  • In the PV (Photovoltaic) power system, a junction box collects the DC voltage generated from the PV module and transfers it to the PCS (power conditioning system). The junction box prevents damage caused by the voltage difference between the serially connected PV modules and provides convenience while repairing or inspecting the PV array. In addition, the junction box uses the diode to protect modules from the inverse current when the PV power system and electric power system are connected for use. However, by using the reverse blocking diode, heat is generated within the junction box while generating electric power, which decreases the generating efficiency, and causes short circuit and electric leakage. In this research, based on the purpose of improving the performance of the PV module by decreasing the heat generation within the junction box, a junction box with a built-in bypass circuit was designed/manufactured so that a certain capacity of current generated from the PV module does not run through the reverse blocking diode. The manufactured junction box was used to compare the electric power and heating power generated when the circuit was in the bypass/non-bypass modes. It was confirmed that the electric power loss and heat generation indicated a decrease when the circuit was in the bypass mode.

Low-Power Cool Bypass Switch for Hot Spot Prevention in Photovoltaic Panels

  • Pennisi, Salvatore;Pulvirenti, Francesco;Scala, Amedeo La
    • ETRI Journal
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    • v.33 no.6
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    • pp.880-886
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    • 2011
  • With the introduction of high-current 8-inch solar cells, conventional Schottky bypass diodes, usually adopted in photovoltaic (PV) panels to prevent the hot spot phenomenon, are becoming ineffective as they cause relatively high voltage drops with associated undue power consumption. In this paper, we present the architecture of an active circuit that reduces the aforementioned power dissipation by profitably replacing the bypass diode through a power MOS switch with its embedded driving circuitry. Experimental prototypes were fabricated and tested, showing that the proposed solution allows a reduction of the power dissipation by more than 70% compared to conventional Schottky diodes. The whole circuit does not require a dedicated DC power and is fully compatible with standard CMOS technologies. This enables its integration, even directly on the panel, thereby opening new scenarios for next generation PV systems.

Clinical Effect of Albumin Addition to the Prime solution in Cardiopulmonary Bypass (체외순환시 산화기 충전액에 첨가된 알부민의 임상적 효과)

  • Lee, Hyeong-Gyo;Yu, Se-Yeong
    • Journal of Chest Surgery
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    • v.23 no.6
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    • pp.1152-1157
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    • 1990
  • Colloid solution is commonly used to increase the oncotic pressures of priming solutions used in the cardiopulmonary bypass circuit. To study the effectiveness of this practice, we retrospectively evaluated 24 patients undergoing cardiac operations to receive isoelectric solution plus 50 gm of albumin[group A], isoelectric solution plus 25 gm of albumin[group B] and isoelectric solution without albumin[group C] as the prime solution for the bypass circuit. Various clinical parameters related to the perioperative fluid balance, cardiopulmonary function, and renal function were studied. There were no differences between the three groups with regard to postoperative clinical parameter of cardiopulmonary, liver function and renal function. But at the previous report by Cho et al. [38], there was a significant difference between groups with regard to hematologic property, especially in crenated red blood cells. These hematologic events did not affect the clinical outcome but thorough evaluations are needed in order to prove the clinical effect of crenated red blood cell. We conclude that there is no clinically detectable advantage for the routinely supplementing of albumin to the priming solution of bypass circuit in cardiac operations. Whether this practice can be of value in selected cases needs to be further studied.

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Electric Circuit Analysis for PV Array on Short-Circuit Failure of Bypass Diode in PV Module (PV모듈의 바이패스 다이오드 단락 고장 시 태양광어레이 회로 특성분석)

  • Lee, Chung-Geun;Shin, Woo-Gyun;Lim, Jong Rok;Hwang, Hye-Mi;Ju, Young-Chul;Jung, Young-Seok;Kang, Gi-Hwan;Chang, Hyo-Sik;Ko, Suk-Whan
    • Journal of the Korean Solar Energy Society
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    • v.39 no.6
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    • pp.15-25
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    • 2019
  • As the installation of photovoltaic systems increases, fire accidents of PV system grow every year. Most of PV system fires have been reported to be caused by electrical components. The majority of fire accidents occurred in combiner box, which is presumed to be short-circuit accidents due to dustproof and waterproof failures or heat deterioration of blocking diode. For this reason, the blocking diode installation became optional by revised PV combiner regulation. In this paper, according to the revised regulation, reverse current that generated by voltage mismatch was measured and analyzed in PV array without a blocking diode. The factors that cause voltage mismatch in array are assumed to be shaded PV module and short circuit failure of bypass diode. As the result of experiment, there is no reverse current to flow under shading condition in module, but reverse current flows on the failure of bypass diode in module. According to the module's I-V characteristic curve analysis, open voltage was slightly reduced due to operation of bypass diode in shading. However, it showed that open circuit voltage has decreased significantly in the failure of bypass diode. This indicates that the difference in open voltage reduction of voltage mismatch factor causes reverse current to flow.

Estimation of Output Power for PV Module with Damaged Bypass Diode using MATLAB (Matlab을 이용한 손상된 바이패스 다이오드가 포함된 PV 모듈의 출력 추정)

  • Shin, Woogyun;Go, Seokhwan;Ju, Youngchul;Chang, Hyosik;Kang, Gihwan
    • Journal of the Korean Solar Energy Society
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    • v.36 no.5
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    • pp.63-71
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    • 2016
  • Installed PV module in field is affected by shading caused by various field environmental factors. Bypass diodes are installed in PV module for preventing a power loss and degradation of PV module by shading. But, Bypass diode is easily damaged by surge voltage and has often initial a defect. This paper propose the electric characteristic variation and the power prediction of PV module with damaged bypass diode. Firstly, the resistance for normal bypass diode and damaged bypass diode of resistance was measured by changing the current. When the current increases, the resistance of normal bypass diode is almost constant but the resistance of damaged bypass diode increases. Next, To estimate power of PV module by damaged bypass diode, the equation for the current is derived using solar cell equivalent circuit. Finally, the derived equation was simulated by using MatLab tools, was verified by comparing experimental data.

Electrical Characteristics of PV Modules with Odd Strings by Arrangement on Bypass Diode (홀수스트링 PV모듈의 바이패스 다이오드 배치에 의한 전기적 특성)

  • Shin, Woo-Gyun;Go, Seok-Hwan;Ju, Young-Chul;Song, Hyung-Jun;Kang, Gi-Hwan
    • Journal of the Korean Solar Energy Society
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    • v.37 no.4
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    • pp.1-11
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    • 2017
  • Most PV modules are fabricated by 6 cell-strings with solar cells connected in series. Moreover, bypass diodes are generally installed every 2 cell-strings to prevent PV modules from a damage induced by current mismatch or partial shading. But, in the case of special purpose PV module, like as BIPV (Building Integrated Photovoltaic), the number of cell-strings per module varies according to its size. Differ from a module employing even cell-strings, the configuration of bypass diode should be optimized in the PV module with odd strings because of oppositely facing electrodes. Hence, in this study, electrical characteristics of special purposed PV module with odd string was empirically and theoretically studied depending on arrangement of bypass diode. Here, we assumed that PV module has 3 strings and the number of bypass diodes in the system varies from 2 to 6. In case of 2 bypass diodes, shading on a center string increases short circuit current of the module, because of a parallel circuit induced by 2 bypass diodes connected to center string. Also, the loss is larger, as the shading area in the center string is enlarged. Thus, maximum power of the PV module with 2 bypass diode decreases by up to 59 (%) when shading area varies from 50 to 90 (%). On the other hand, In case of 3 and 6 bypass diodes, the maximum power reduction was within about 3 (W), even the shading area changes from 50 to 90 (%). As a result, It is an alternative to arrange the bypass diode by each string or one bypass diode in the PV module in order to completely bypass current in case of shading, when PV module with odd string are fabricated.