HIGH-FREQUENCY VOLTAGE STRESS OF INSULATION - METHODS OF TESTING

Traditionally high electrical stress of insulation occurs in HV equipment. Usually this stress is 50/60 Hz ac and rather seldom dc. Exceptional situations may occur in rf transmitters. This is very different in low voltage equipment. Due to the increased use of high-power semiconductors with high cutoff frequency, working voltages of rather high amplitudes and with frequencies > 100 kHz occur frequently. Also, the distances through solid insulation may be rather low resulting in electrical fields in excess of those being typical for HV equipment. In combination with such hf working voltages, this means an extraordinary stress for the insulation. As there is a strong economical interest in further miniaturization, those problems have to be analyzed more precisely. The most important data about hf stress of insulation, which are readily available until now, are summarized in this paper.