• 한국신재생에너지학회:학술대회논문집
• /
• 2007.06a
• /
• pp.423-426
• /
• 2007

Pohang Wind Energy Research Center (PoWER-C) is developing a 3 MW Radial Flux Permanent Magnet (RFPM) Synchronous Generator for offshore Wind Energy Converter (WEC). The rotor rpm is 15.7 and the gear ratio is set to be 92.93. The nominal generator rpm at the rated load is about 1459. To reduce the switching loss in the power electronics, the maximum frequency is limited to 100 Hz. This requirement limits the number of pole to six or eight. Permanent magnet excitation is assumed for higher energy yield and higher efficiency. In this report, the requirements and the first efforts for the physics design are described.

• Proceedings of the Korean Society for Agricultural Machinery Conference
• /
• 2003.07a
• /
• pp.232-237
• /
• 2003

Sound has been rated negatively in many industrial areas as the noise to be removed. In the agricultural process such as rice milling based on grinding the surface of the rice, however, it may be anticipated that the sound can contain the some information on the process. In this research, on the assumption that variation of the shape of the rice kernel during milling may bring the change in frequency characteristic of sound signal, we tried to investigate the relationship between the milling degree in the grinding test mill and the resonance and anti-resonance frequencies (the frequencies at which the sound power has the extreme values). (omitted)

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.62 no.5
• /
• pp.626-631
• /
• 2013

Gas turbine systems are applied extensively in energy supplies to cover peak load requirements. The gas turboset must be accelerated by starting device up to 60%~80% of rated speed to ignite the gas turbine. Recently, the most favorable and economical starting device is the LCI(Load Commutated Inverter). The LCI runs up the gas turboset by feeding the generator as a synchronous motor. In this paper, we discuss in detail the driving principles and features of 183MW gas turbine system. During field application of LCI system, many tests have been conducted and the results were described in this paper. The test results will be considered as the important resources for development in future.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.27 no.6
• /
• pp.9-16
• /
• 2013

This paper presents an operating characteristics of the 5-phase 5kW with developed the surface permanent magnetic synchronous generato (SPMSG) in order to make a study of a polyphase ac motors keeping hold of more advantages. There are shown a amplitude and waveform of the generated electromotive force, in FFT analysis of harmonics, within output voltages, and reviewing a experiment results in no-load test, resistive load, and inductive load using 5-phase induction motor by variable output frequency. The operating characteristics of the developed manufacturing generator include voltage regulation, efficiency, power factor, THD, and so on at rated load.

• Proceedings of the KIPE Conference
• /
• 2004.11a
• /
• pp.27-31
• /
• 2004

This paper presents a nonconventional method for oft starting of three-phase induction motors, which achieved by flux weakening technique. flux weakening is not done by reducing the applied voltage as in the conventional methods, Flus weakening is achieved y increasing the supply frequency over the rated value while the voltage amplitude is kept constant. This method has advantage of reducing the stress on the electrical and mechanical systems. The feasibility of this basic idea has been confirmed through investigating the starting transient corresponding to this mode of operation. For this purpose, a rigorous state space mathematical model has been developed and simulated. The validity of the proposed method through the results from the mathematical model have been confirmed experimentally.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.30 no.4
• /
• pp.253-257
• /
• 2017

Nowadays, it is increasingly important to detect whether cables are live for the operator's safety if there is a sudden power failure. It is especially hard to detect the electrical field of an underground line because of shielding. This paper on detection of live-line states in cables studied the detection characteristics of the change in the magnetic field and axis as the frequency, voltage, and distance at the same load are changed using 3 axes. A search coil type was used as a magnetic field sensor with non-contact. We found that magnetic fields decrease proportionally to the square of the distance and the decrease of rated voltage with load effected to magnetic field. The magnetic field was detected by 3-axis sensors given correct proximity, but appeared as noise components beyond a distance of 2 cm.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.48 no.8
• /
• pp.417-425
• /
• 1999

This paper presents an effective control scheme with the voltage-fed half-bridge series resonant inverter for induction heating system, which is based upon a load-adaptive tuned frequency tracking control strategy using PLL(Phase Locked Loop) and its peripheral control circuits. The proposed control strategy ensures a stable operation characteristics of overall inverter system and ZVS(Zero Voltage Switching) irrespective of sensitive load parameter variations, specially in the non-magnetic materials as well as power regulation. The detail operation principle and the characteristics of inverter system with the proposed control scheme are described and its validity is verified by the simulation and the experimental results for a prototype induction cooking system rated at 1.2kW.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.28 no.1
• /
• pp.36-44
• /
• 2014

The conventional central photo voltaic inverters have several problems. First, shadow problem in each solar panel, and high DC voltage problem from each panel because of concentration to one central inverter. Therefore, module integrated inverter is proposed to solve these problems. The inverter should be small and cost effective. The cost and size in the inverter depend on the inductor. So the switching frequency should be increased to reduce the inductor and total size, but there is a problem in efficiency because of the losses in turn-on and turn-off. In the paper, the critical conduction mode(CRM) switching method is adopted to reduce the switching loss and interleaving method is proposed to increase the efficiency in Flyback converter. Finally, the validity of the proposed scheme is investigated with simulated and experimental results for a prototype system rated at 200W.

• Proceedings of the KIEE Conference
• /
• 2005.07b
• /
• pp.1416-1418
• /
• 2005

This paper presents a new hybrid control method of asymmetrical half-bridge converter(AHBC) with low voltage stresses of the diodes and interleaved PFC(power factor correction). The proposed new control scheme can observe variation of secondary diodes voltage stresses by variation of duty ratio and then decide the control portions which are asymmetrical control and PFM(Pulse Frequency Modulation). Therefore, the proposed control scheme has many advantages such as a low rated voltage of the secondary diodes, low conduction loss according to the low voltage drop and wide zvs range by load variation. Through simulation results, the validity of the proposed control scheme is demonstrated.

• Journal of Power Electronics
• /
• v.13 no.4
• /
• pp.626-635
• /
• 2013

An analysis of the junction capacitance in resonant rectifiers which has a significant impact on the operating point of resonance circuits is studied in this paper, where the junction capacitance of the rectifier diode is to decrease the resonant current and output voltage in the circuit when compared with that in an ideal rectifier diode. This can be represented by a simplified series resonant equivalent circuit and a voltage transfer function versus the normalized operating frequency at varied values of the resonant capacitor. A low voltage to high voltage push-pull DC/DC resonant converter was used as a design example. The design procedure is based on the principle of the half bridge class-DE resonant rectifier, which ensures more accurate results. The proposed scheme provides a more systematic and feasible solution than the conventional resonant push-pull DC/DC converter analysis methodology. To increase circuit efficiency, the main switches and the rectifier diodes can be operated under the zero-voltage and zero-current switching conditions, respectively. In order to achieve this objective, the parameters of the DC/DC converter need to be designed properly. The details of the analysis and design of this DC/DC converter's components are described. A prototype was constructed with a 62-88 kHz variable switching frequency, a 12 $V_{DC}$ input voltage, a 380 $V_{DC}$ output voltage, and a rated output power of 150 W. The validity of this approach was confirmed by simulation and experimental results.