Varistor energy calculation

The energy absorbed by the varistor can be calculated by:

W=K.I.U.T(J)

Where: I - peak current flowing through the varistor;

U-- the voltage developed across the varistor when it flows through circuit I;

T - the duration of current I;

The K--waveform factor for the square wave of 2ms, K = 1; for the 8/20μs wave, K = 1.4; for the 10/1000μs wave, K ≈ 1.4.

In practical applications, the energy stored in the circuit (such as the energy on coils and capacitors, and stray energy) requires varistors to absorb. When this happens, the varistor must be chosen so that the total energy stored in the circuit is less than the energy that the varistor can absorb.

The current production of varistors due to the different varieties, the great difference in their capacitance, so the selection does not affect the normal operation of the principle of the circuit. The general varistor is suitable for use at 300Hz frequency.