Power conditioning for pulsed high voltage generation from capacitor bank by using fuse opening switch (FOS) and tape-wound transformer

Abstract

Multi-channel spark gap switch has been widely used in high current and low inductance pulse forming network to obtain switching of fast rise time and high current pulses. Inductance and resistance of a spark gap switch are rapidly decreased with increase of channels and electrode erosion is reduced hy lower current density. In this work, electrically multi-triggered spark gap switch was developed to be used as a multi-channel spark gap switch in 2-15 kJ plasma focus device with a capacitor of Maxwell No. 32169 (capacitance; 32 uF, inductance 65 nH). The geometry of multi-triggered spark gap switch is similar to an annular-type rail gap switch. The large bodies of dielectric that surround the electrodes were designed to prevent arcing along the exterior of the gap. The dielectric material is translucent polycarbonate which has high Izod impact strength. By using the translucent polycarbonate, breakdown in the gap switch could be visually observed, The main electrodes and trigger are made of stainless steel. The minimum gap spacing in this switch is 7mm and the trigger is located between two main electrodes. The trigger is similar to the main electrode of trigatron switch. In parenthesis, five different trigger-pins are located in main trigger-plate and these are isolated with dielectric material. Therefore, sixdifferent trigger signals can he generated with time difference of a few micro-second. painhyunQihanyang.sckr , Agency for Defense Development Yvseong P. 0. 80235-5, Taejon, 305-600 KoreaWhen pulsed power is supplied to a high-impedance load from a capacitor hank, power-condtioning devices are required in order to convert slow high-current into fast highvoltage. Most widely used power-conditioning devices are opening switches, closing switches, and transformers. We designed a fuse opening switch (FOS) and a tape-wound transformer to obtain a high voltage pulse from a capacitor bank.The FOS was made of a layer of copper foil as a fuse and two layers of PTFE (ploytetrafluoroethylene) films as a quenching medium. The copper foil was sandwiched tightly with two PTFE sheets by adhesive tape. An au-core type transformer was adopted in order to avoid problems associated with high magnetic field. Copper sheets coated two times with polyester films were wound by 1 turn for the primary and 16.5 turns for the secondary coils of the transformer. We assembled the capacitor bank, the FOS, the transformer, and a resistive load, in series, and tested the assembled system. Peak current of 150 kA was supplied from the capacitor bank of 75 pF charged at 19 kV to the primary coil of the transformer through the FOS. The current was rapidly interrupted hy rupture of the FOS, and induced high di/dt and consequently high voltage, 38 kV at the primary coil and 330 kV at the secondary coil of the transformer connected to a resistive load of 300 R. The FWHM (full width half maximum) of the load voltage was 0.9 #s. Experimental details and results will be presented.at the conference. t .tdokimOadd.re. kr 308