• 전기학회논문지
• /
• 제57권12호
• /
• pp.2173-2178
• /
• 2008

A doubly-fed induction generator(DFIG) system has been widely used in the modem wind turbines due to variable-speed operation, high efficiency and small converter size. It is well known that an inter-turn fault of a generator is very difficult to be detected. The DFIG system uses a wound rotor induction machine so that the magnetizing current of the generator can be fed from both the stator and the rotor. This paper proposes a protection algorithm for a DFIG using the d-q equivalent circuit in the time domain. In the case of a DFIG, the voltages and currents of the rotor side as well as the voltages and currents of the stator are available. The proposed algorithm estimates the instantaneous(i.e., converted into the stationary frame) induced voltages from the rotor and the stator sides. If the difference between the two estimated induced voltages exceeds the threshold, the proposed algorithm detects the inter-turn fault. The algorithm can detect a inter-turn fault of a winding. The performance of the proposed algorithm is validated using a PSCAD/EMTDC simulator under inter-turn fault conditions and normal operating conditions such as an external fault and the change of the wind speed.

• Journal of Magnetics
• /
• 제20권2호
• /
• pp.176-185
• /
• 2015

We present the design optimization of the magnetic pole and slot design options that minimize the cogging torque of permanent-magnet (PM) brushless generators for small wind turbine generators. Most small wind-turbines use direct-driven PM generators which have the characteristics of low speed and high efficiency. Small wind-turbines are usually self-starting and require very simple controls. The cogging torque is an inherent characteristic of PM generators, and is mainly caused by the generator's geometry. The inherent the cogging torque can cause problems during turbine start-up and cut-in in order to start softly and to run a power generator even when there is little wind power during turbine start-up. Thus, to improve the operation of small turbines, it is important to minimize the cogging torque. To determine the effects of the cogging torque reductions, we adjust the slot opening width, slot skewing, mounting method of magnets, magnet shape, and the opening and combinations of different numbers of slots per pole. Of these different methods, we combine the methods and optimized the design variables for the most significant design options affecting the cogging torque. Finally, we apply to the target design model and compare FEA simulation and measured results to validate the design optimization.

• 조명전기설비학회논문지
• /
• 제30권2호
• /
• pp.71-77
• /
• 2016

The dielectric barrier discharge (DBD) has low efficiency due to about 70% input power is consumed as thermal energy in the discharge space. However, because of the usage of DBD ozone generator is easier than other methods. The DBD ozone generator has been widely applied for high concentration ozone generation in the industrial application. But, the low-capacity compact DBD ozone generator is not applied so far. Therefore, the DBD ozone generator is necessary to improve ozone production efficiency and reduce the capacity. In this paper, the stainless steel pipe inner electrode was designed with hall type and screw type to improve the ozone production yield. The manufactured two inner electrodes were experimented with normal type for comparison of the discharge characteristics and the ozone generating characteristics. As the experimental results, the discharge current effective value of designed inner electrodes with hall type and screw type are higher than the normal type, due to unequal electric field is formed at the boundary. However, the difference of designed and original electrodes is less than 0.1mA that has no effect on the discharge characteristic. On the other hand, the screw type inner electrode increased higher than original model about 7 times when the flow rate of the oxygen source gas was increased from $0.6{\ell}/min$ to $1.0{\ell}/min$ The reason was assumed by the flow rate of the raw gas through the inner electrode was became fast that has a cooling effect. The designed hall type and screw type inner electrodes have shown good performances in ozone generation and ozone production that better than normal type in the same electrode surface area.

• 디지털융복합연구
• /
• 제14권9호
• /
• pp.281-286
• /
• 2016

본 논문에서는 수소수 생성기 구조설계를 최적화하여, 세계 최고 수준의 용존수소량(1,000~1,200 ppb)을 보유한 수소수생성기를 개발하여 평가하였다. 평가는 용존수소량, 산도, 최대수압, 산화환원전위 등 4가지로 나누어 각각의 목표치를 잡아서 평가하였다. 실험결과는 4가지 모두 5차례의 실험을 통하여 시행하였고, 모두 목표치 범위 안에서 결과가 나타나 그 우수성을 입증하였다. 또한 기능성 평가에 있어서도 그 결과는 기능성은 25/30점, 유지보수성은 17/20, 사용성은 26/30점. 효율성은 19/20점으로 나타났으며, 특히 효율성이 높게 나타나서 본 연구의 타당성을 증명하였다. 본 논문은 이러한 수소수 생성기를 즉시 출수 가능한 시스템으로 개발하여 정수기 대체재로 사용 가능하도록 하였다.

• 전기학회논문지P
• /
• 제58권4호
• /
• pp.588-591
• /
• 2009

We had experimental studies of microwave output generator. We experimented with a corrugate-shped K-band slow wave guide in the backward wave oscillator. It generated output 표 interaction between electron beam's generation and magnetic field. We estimated oscillation frequency at 24GHz by changing propagation velocity and group velocity. We identified movement by second harmonic of Cherencov interaction and slow cyclotron mode. In our study we achieved oscillation stabilization, generation of long pulse, improvement of oscillation efficiency and output.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2007년도 추계학술대회 논문집
• /
• pp.481-481
• /
• 2007

The characteristics of slow wave structure employed for backward wave oscillator expected to be a high power microwave source are studied analytically. The slow wave structure is a sinusodially corrugated wall waveguide. The waveguide is designed and transmitted characteristics for microwave are measured in the air. There exist literatures on high efficiency of enhansed radiation from backward wave oscillators involving plasmastudied experimentally another results.

• 산업융합연구
• /
• 제22권7호
• /
• pp.15-21
• /
• 2024

등산스틱은 일반적으로 산행하는 등산객 등이 보행 시 자신의 신체를 의지하면서 보행이 가능하도록 하는 보행 보조도구의 하나이다. 이러한 보조기구인 등산스틱에 다양한 기능을 수행할 수 있도록 하기 위해 충전용 배터리가 내장되어야 한다. 충전용 배터리를 충전하기 위해 별도의 전원공급장치가 필요하다. 본 연구는 자가발전 전원장치에 대한 것으로 기존의 방식보다 발전효율이 높은 스크루를 이용한 발전장치를 개발한다. 기존의 발전 방식 등과 비교 분석하고 이에 대한 문제점을 파악하여 본 연구에서 제시한 방식과 차별화를 둔다. 스크루 방식의 발전장치는 등산스틱이 지면에 접촉할 때와 지면과 떨어질 때 발전하도록 한다. 발전장치의 내장으로 별도의 전원공급장치가 필요 없고, 휴대폰 보조배터리의 역할과 조명등을 부착하여 사용할 수 있고, GPS 센서 등을 내장하여 위치 추적을 통해 길을 잃었을 때 찾을 수 있고 조명을 이용해 조난 등 위급한 상황에서 사용자의 안전을 지킬 수 있는 효과가 있다. 기존의 등산스틱 내장형 발전장치는 전류가 매우 약해 충전이 어렵고 실용성이 낫다. 본 연구에서 개발한 발전장치는 고효율을 실현하여 충분한 전류를 얻을 수 있어 배터리 충전이 가능하고 실용성이 높다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
• /
• 제52권4호
• /
• pp.161-169
• /
• 2003

The applications of SRM(Switched Reluctance motor) are dramatically increasing due to a simple mechanical structure, a high efficiency and a high speed drive characteristics. Energy recovery in the regenerative region is very important when SRM is used in traction drive. This is to reduce energy loss during mechanical braking and/or to have a high efficiency drive. To control excitation voltage during motoring and regenerating voltage in the generator operation in the SRM, multi-level voltage control is effective. This paper suggests multi-level inverter which is useful for motoring and regenerative operation. The proposed method is verified through simulations and experiments.

• 대한전기학회논문지:전력기술부문A
• /
• 제52권4호
• /
• pp.161-161
• /
• 2003

The applications of SRM(Switched Reluctance motor) are dramatically increasing due to a simple mechanical structure, a high efficiency and a high speed drive characteristics. Energy recovery in the regenerative region is very important when SRM is used in traction drive. This is to reduce energy loss during mechanical braking and/or to have a high efficiency drive. To control excitation voltage during motoring and regenerating voltage in the generator operation in the SRM, multi-level voltage control is effective. This paper suggests multi-level inverter which is useful for motoring and regenerative operation. The proposed method is verified through simulations and experiments.

• 전력전자학회논문지
• /
• 제17권5호
• /
• pp.431-437
• /
• 2012

PV simulators are essential equipment for testing power conditioning systems (PCS) which are one of an important part in PV generator systems, for testing before shipment. High dynamic PV simulator is required since MPPT(Maximum Power Point Tracking) test procedure has been established by EN50530 regulation recently. Most high quality PV simulator prevailed in the market is linear type which however has low efficiency. This paper proposes design guide lines for the power stage and LCL type filter cooperating with a switching mode PV simulator that shows high efficiency and very low power consumption. Proposed theory is verified by experiment.