Varistor selection.

Minimum reference voltage: Ulma≥(1.8～2) Uac (used under DC conditions)

　　Ulma≥(2.2～2.5) Uac (used under AC conditions, Uac is AC working voltage)

The maximum reference voltage of the varistor should be determined by the withstand voltage of the protected electronic device, and the residual voltage of the varistor should be lower than the loss voltage level of the protected electronic device, that is (Ulma)max≤Ub/K, above Where K is the residual voltage ratio, Ub is the loss voltage of the protected equipment.

36VMAX, generally choose a MOV of about 50V, such as Langtuo's LT14D540K. MOV has relatively few gears around 50V, and it is recommended to use LTSMCJ43CA.

The maximum voltage of 36V generally chooses a 470 varistor, and you need to determine the type of your varistor according to the withstand voltage of your back-end circuit and the surge power of the input power supply, which can be slightly relaxed.