Search

The triggered vacuum gap (TVG) is a closing switch for generating large current pulse and can work in the wide range of voltage for several kV to tens kV. Main electrodes are made of Ag-WC. One of main electrode has a hole for trigger electrode (Mo). The switching time is short, if the polarity of the holed-electrode is negative. It is called polarity effect. We devised a crowbar circuit using the polarity effect of the TVGs. The crowbar current of this circuit was investigated experimentally by varying applied voltage, inductance, capacitance, gap length of TVGs, and trigger current duration. A crowbar current, crest of which is 2.4 kA and 4.9/270µs for example, was observed. The probability of generating the crowbar current was more than about 90 %, in the following condition: the trigger current duration of 6.65 µs and the gap length of 2-6 mm.

Both switching time and minimum firing voltage of a triggered vacuum gap employing a trigger electrode in the cathode and anode (double triggered vacuum gap) were measured. The double triggered vacuum gap was operated below 100 V independent of the high voltage main electrode polarity (positive or negative). This minimum firing voltage was lower than that of the conventional triggered vacuum gap. The switching time is approximately 0.5 μs in the range 3 to 18 kV. The conventional triggered vacuum gap has a trigger electrode that is placed at the center of the grounded main electrode. The polarity of the main electrode affected switching time characteristics. A trigger electrode was added to the high voltage main electrode. The double triggered vacuum gap was only slightly influenced by the polarity of the high voltage main electrode when both main electrodes were triggered at the same time.