ISSN 1203-8407 © 2007 Science & Technology Network, Inc. J. Adv. Oxid. Technol. Vol. 10, No. 2, 2007 311 Duty Factor Effect on Ozone Production Using Dielectric Barrier Discharge Reactor Driven by IGBT Pulse Modulator T. Miura, T. Sato 1 , K. Arima 1 , S. Mukaigawa 1 , K. Takaki 1 , and T. Fujiwara 1 Technical Research Department, SAWAFUJI ELECTRIC CO., LTD., 3, Nittahayakawa cho, Ota City, Gunma, 370-0344, Japan 1 Department of Electrical and Electronic Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020- 8551, Japan Abstract: An ozone production using pulse voltage driven dielectric barrier discharge (DBD) reactor was investigated experimentally to clarify an influence of a duty factor of applied pulse voltage on ozone yield. A square of 10 kV applied voltage was generated using a pulse modulator. Insulated gate bipolar transistor (IGBT) switches were employed to generate the square pulse with 1 kHz in pulse repetition rate. Duty factor of the pulse voltage was controlled in range from 10 to 80% by timing of a gate signal to the IGBT switches. The output voltages of the power supply were applied to a multipoint electrode type DBD reactor in order to operate at low applied voltage. The ozone yield was obtained to be around 100 g/kWh at several thousands ppm ozone produc- tion in pure oxygen circumstance at 5 L/min. gas flow. The ozone yield decreased with increasing ozone concentration and was almost independent of the duty factor of square applied voltage under the present experimental condition. Power loss consumed in the pulse modulator was successfully reduced by decreasing duty factor of the output voltage without decrease of the ozone production. Introduction It is well known that high-pressure dielectric barrier discharges (DBD; so-called silent discharge) have become one of the powerful methods for ozone production since the pioneering work by Siemens (1). So far, there have been many attempts to improve the efficiency of ozone production, leading to industrial uses of such discharges (2). The efficiency depends on the gas pressure, the temperature, and the gas used as well as the discharge conditions such as gap-width, electrode surface, electrode material including a dielectric barrier, and an applied voltage waveform (3-5). Some researchers reported that the application of pulse voltages was effective to achieve high yield of ozone production (6). The application of pulse vol- tages emphases the highly distorted high electric field near a head of a streamer discharge, as the results, the streamer head contains high energy electrons (6, 7). Moreover, a loss in the dielectric barrier is expected to be reduced by employment of pulse waveforms as applied voltage owing to a short duration of rise and fall phases of the applied voltage. However, an influence of duty factor, which is defined by a ratio of a voltage-on time to an inverse number of the applied voltage frequency, on an energy transfer efficiency of the power supply with DBD reactor as a load is not clear. Keywords: ozone, DBD, pulse modulator, ozone yield, efficiency, non-thermal plasma This paper describes the results of experimental study on ozone production using pulse voltage driven DBD reactor to clarify an influence of applied vol- tage pulse width on ozone yield including power transfer efficiency of the power supply. Experimental Setup Pulse Modulator Figure 1 shows equivalent circuit of the pulse modulator employed to drive the DBD reactor for ozone production. The pulse modulator generates a square wave pulse with various duty factors. A three- phase 50 Hz sinusoidal voltage is rectified using a diode bridge. The rectified voltage is applied to a primary energy storage capacitor C. This part works as an AC/DC converter with maximum voltage of 300V. Four insulated gate bipolar transistor (IGBT) switches are used as repetitive closing switch to generate a square waveform voltage. This part is worked as DC/AC inverter. The pulse width i.e. the duty factor is controlled by timing of applying gate pulse to the IGBT switches. The pulse repetition rate is fixed at 1 kHz. The output voltage of 300 V is amplified to 10 kV using pulse transformer. This voltage is applied to the DBD load to produce ozone. Figure 2 shows typical output voltage of the pulse modulator for two different pulse widths i.e. duty factors. A resistor of 180 kΩ is used as high impedance load in this case. The pulse width is successfully controlled from 50 to 400 µs i.e. from 10 to 80% of Brought to you by | University of Michigan Authenticated Download Date | 1/29/17 9:10 PM