電気絶縁材料の耐アーク性に及ぼす印加電圧波形の影響

Abstract

There are many cases that the alternating voltage applied on the practical electrical machines contains not only constant amplitude sinusoidal waves but also distorted waves or high frequency-superimposed waves. Therefore, the real appraisal of arc resistance of insulating materials for such applications is difficult to make on the basis of arc resistance determined by the conventional test under sinusoidal wave voltage.In this paper, the arc resistance under distorted wave voltage and high frequency-superimposed wave voltage were investigated. The test method was similar to the high voltage low current arc resistance test like the ASTM method. However, the test method using the triac was tried in order to search for a reliable arc resistance test which incorporates the merits of the electrical static type interrupter of circuit and compensates the weakness of the mechanical intermittent interrupter. The applied voltage, arc current and arc intermittent time of the fundamental waves for the high voltage low current arc test were the same as used in the ASTM method. The electrode type was the rod type and the electrode gap length was 6.4mm. To generate distorted wave voltage and high frequency-superimposed one, the voltage from the oscilator was amplified separately as in Fig. 2 and was superimposed to the fundamental sinusoidal wave at the secondary side of the transformer.The results of the tests show that the arc resistance decreased with increasing frequency of the superimposed wave and also with increasing crest value of the waves at a constant frequency, when the high frequency voltage was superimposed and its crest value was about 4-20% of the fundamental sinusoidal wave voltage. Furthermore, the above arc resistance was lower than the one at the smooth sinusoidal wave voltage with the same maximum and minimum voltages.