How To Choose A Varistor
Feb 28, 2021
Generally speaking, the varistor is often used in parallel with the protected device or device. Under normal circumstances, the DC or AC voltage across the varistor should be lower than the nominal voltage, even when the power supply fluctuates the worst.
It should not be higher than the maximum continuous working voltage selected in the rated value, and the nominal voltage value corresponding to the maximum continuous working voltage value is the selected value. For the application of overvoltage protection, the varistor voltage value should be greater than the voltage value of the actual circuit.
Generally, the following formula should be used to select: VmA=av/bc where: a is the circuit voltage fluctuation coefficient; v is the DC working voltage of the circuit ( AC is the effective value; b is the varistor voltage error; c is the aging coefficient of the component; the actual value of VmA calculated in this way is 1.5 times the DC working voltage, and the peak value should be considered in the AC state, so the calculation result should be expanded 1.414 times.
