Selection technique of varistor: nominal voltage selection

 In general, varistors are often used in parallel with protected devices or devices, and under normal circumstances the DC or AC voltages at both ends of the varistors should be lower than the nominal voltage, even in the worst case of power fluctuations. Nor should it be higher than the maximum continuous working voltage selected in the rating. The nominal voltage value corresponding to the maximum continuous working voltage value is the selected value. For the application of overvoltage protection, the voltage-sensitive voltage value should be larger than the actual circuit voltage value, and the following formula should be used to select the voltage fluctuation coefficient of the circuit. Generally 1.2; V is the DC working voltage of the circuit. B is the varistor voltage error, generally taking 0.85; C is the aging coefficient of the element, generally take 0.9; The actual value of VmA calculated in this way is 1. 5 times of DC working voltage, and the peak value should be considered in AC state. Therefore, the calculated results should be expanded by 1. 414 times.