Behavior of low voltage varistors under very fast oscillatory type current impulse environment

In this study, the behavior of low voltage varistors under very fast oscillatory type non standard current impulses were analyzed. The experiment was performed on 20 mm disk varistors with different nominal operating voltages of 14V, 30 V, 40 V, 75 V, 150 V, 250 V and 275 V. Non standard current impulses were generated using a Van De Graaff generator. The shape of the impulse was like a double exponential oscillatory type wave which has the oscillation frequency of 14.53 MHz. The rise time of the impulse was 8 ns with a maximum peak current rate-of-rise is of 2.41 × 10¹¹ A/s. According to the results, under vary fast non standard current impulse environment, clamping voltage could be depend on both nominal voltage of varistors as well as its disk diameter. Another important feature of the voltage signatures observed was the DC offset voltage causes between terminals of varistor immediately after it triggered due injected fast current impulses.