• Proceedings of the KIEE Conference
• /
• 2005.07b
• /
• pp.1530-1533
• /
• 2005

Total 12 units of high power klystron-modulator systems as microwave source is under operation for 2.5-GeV electron linear accelerator in Pohang Light Source(PLS) linac. RF power and beam power of klystron are precisely measured for the effective control of electron beam. A precise measurement and measurement equipment with good response characteristics are required for this. Input power of klystron is calculated from the applied voltage and the current on its cathode. Tiny measurement error severely effects RF output power value of klystron. Therefore, special care is needed to measure precise beam voltage. Capacitive voltage divider(CVD) unit is intended for the measurement of beam voltage of 400 kV generated from the pulsed klystron-modulator system. Main parameter to determine the standard capacitance in the high arm of CVD is dielectric constant of insulation oil. Therefore CVD should be designed to have a minimum capacitance variation due to voltage, frequency and temperature in the measurement range. This paper will discuss the analysis of capacitive voltage divider for a pulsed high-voltage measurement, and the empirical relations between capacitance and oil temperature variation.

• Journal of Power Electronics
• /
• v.17 no.4
• /
• pp.923-932
• /
• 2017

This paper proposes a novel scheme which can compensate the common-mode voltage (CMV) for five-level active neutralpoint clamped (5L-ANPC) inverters, which is based on modifying the space vector pulse width modulation (SVPWM) and adding an auxiliary leg to the inverter. For the modified SVPWM, only the 55 voltage vectors producing low CMV values among the 125 possible voltage vectors are utilized, which varies over the three voltage levels of $-V_{dc}/12$, 0 V, and $V_{dc}/12$. In addition, the compensating voltage, which is injected into the 5L-ANPC inverter system to cancel the remaining CVM through a common-mode transformer (CMT) is generated by the additional NPC leg. By the proposed method, the CMV of the inverter is fully eliminated, while the utilization of the DC-link voltage is not decreased at all. Furthermore, all of the DC-link and flying capacitor voltages of the inverter are well controlled. Simulation and experimental results have verified the validity of the proposed scheme.

• Proceedings of the KIEE Conference
• /
• summer
• /
• pp.205-207
• /
• 2004

This paper proposes a new SSHG(Sag/swell and Harmonic Generator) injecting voltage by using series inverter. The proposed SSHG composes series inverter, DC capacitor as energy storage, rectifier and voltage clamp circuit. This SSHG is designed to generate typical power disturbances, such as voltage sag/swell, over/under voltage and voltage flicker. Also it is designed to generate unexpected voltage phase jumping waveform by controlling the series inverter. In this paper, three kinds of control methods for the proposed 2MVA SSHG are given. Typical voltage sag and swell waveforms are implemented by adopting simple control method. Also the voltage flicker is generated by changing the amplitude of the injected voltage in random. Owing to the limited bandwith of the proposed SSHG, high frequency transient waveforms can be obtained by using the open loop control. The simulation and experimental results are given to verify the operation of the proposed SSHG, Finally, conclusions are given.

• Proceedings of the KIEE Conference
• /
• 1992.07b
• /
• pp.669-672
• /
• 1992

The increasing application of Vacuum Circuit-Breakers (VCB) on utility and industrial systems has prompted and detailed investigation of vacuum switching surge mechanisms and protections. This paper arranges arc-extinguishing principles of magnetic field in vacuum in order to disperse rapidly arc generated from vacuum contacts on switching VCR and plans establishment of protection means to protect high-voltage motor against surge voltage magnitude and transient voltage rate of rise

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.58 no.1
• /
• pp.38-43
• /
• 2009

Reactors are connected with capacitors to passive filter circuits for reducing harmonics caused by power conversion application. This passive filter frequently gets out of order by voltage and current stress. Especially filter reactor has too much voltage harmonics components, its trouble rate is higher than capacitor. In this paper, we analyzed voltage and current of reactor and capacitor used for passive filter by simulation and measurement. If reactor has a tolerance on variation of reactance value, series resonance frequency is different from originally filter design frequency and parallel resonance can be generated at the close point of the former. Because filter absorbs harmonic component of non-linear load, much of harmonic voltage has been impacted on reactor.

• 한국연소학회:학술대회논문집
• /
• 2004.06a
• /
• pp.83-88
• /
• 2004

High voltage AC electric field has been applied to turbulent propane jets to investigate the effect of electric field on liftoff characteristics. Liftoff velocity and liftoff height have been measured by varying the applied voltage and frequency. Liftoff velocities were delayed and liftoff heights were reduced by applying AC, not by DC. The electric effect became disappeared with further increasing jet velocities, which shows that the effect can be explained by the balance between inertia force and electric force. The flame stabilization effect was intensified as either applied voltage or frequency increased. Plasma streamers were generated between the flame and the jet under high voltage conditions. Liftoff velocity in the absence of plasma can be well correlated by the function of voltage and frequency.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07b
• /
• pp.595-598
• /
• 2004

We have explained Process and electrical characteristics of a step-down Rosen type piezoelectric transformer for AC-adapter. When the electric voltage is applied to the driving piezoelectric vibrator notarized in the thickness direction, then output voltage is generated at the generating piezoelectric vibrator polarized in the thickness direction due to the piezoelectric effects. Output voltage and current from a single-layered piezoelectric transformer were measured under the various condition of loads and frequencies It was shown from experiments that output voltage has increased and resonance frequency has changed according to various resistor loads. Output current has decreased inversely proportional to the loads

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.23 no.3
• /
• pp.250-259
• /
• 2010

The ability for energy harvesting via the piezoelectric effect was studied for a unimorph element such as piezo buzzer. A simple equivalent circuit was proposed to predict the energy generated based on the internal stress. Unimorphs with a metal-cavity were used as a driving device of the generation panel. Both the AC open voltage and DC output voltage as a function of pressure period and number of element were measured. For the unimorph generation circuit, DC output voltage varies with pressure period, reaching a maximum value at $470{\mu}F$. The maximum output voltage a according to load resistance was measured at $1M{\Omega}$. Data analysis of the DC output voltage and time constant indicated that number of piezoelectric element of optimum was 60~80. It was found that piezoelectric unimorph has the possibility to be used as the driving element of the electric generation.

• New & Renewable Energy
• /
• v.2 no.3
• /
• pp.5-9
• /
• 2006

We have fabricated a micro power generator which changes vibrational energy into useful energy. With vibrating a magnet on the surface of a winding coil, the micro power generator produce alternating voltage. We have changed the vibrational frequency from 0.5Hz to 10Hz. AC voltage of $20{\sim}25mV$ was generated at the frequency of 1Hz. When the vibration was 3Hz, AC voltage of 80mV was obtained. We have rectified and stepped up the input voltage using a quadrupler circuit. The voltage was stepped up to 130mV.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.24 no.1
• /
• pp.124-129
• /
• 2015

The performance of a passenger vehicle has been greatly improved recently owing to the intensive use of electronic controllers. Many components of a vehicle, including the engine, are controlled by electronic systems installed in the vehicle. Therefore, the electrical power required for such electronics has increased significantly. However, the electrical power generated by the vehicle's alternator, operated by the engine, is limited, and when the vehicle is started, a large instantaneous current is required. The voltage of the vehicle electrical system fluctuates to a very low level, then, it is gradually recovered. This case is very severe and can even cause damage to electronic systems. In this study, a voltage-stabilizing module comprising electric double layer supercapacitors, which could alleviate the voltage variation, was developed and tested.