The Varistors library is one of the component library types within the Component Library included in PI Expert.. Once a Metal Oxide Varistor (MOV) is added to the library and included in a Component Set, you can manually choose your varistor to be used where applicable. Varistors are used to limit the excessive transient voltages by shunting the current created by a surge protecting the remaining components within the power supply.
PI Expert does not allow you to modify or delete the default components. You can only view the parameters of a selected component type by clicking the View button. You can add custom components to the Component Library by clicking the Add button in the Component Library dialog where you can input all relevant specifications for a particular component. See the Component Library topic for more information on adding and editing components.
You can specify the following parameters to add a varistor:
Type - Varistor type
Rated Voltage - Varistor rated voltage in Volt (V)
Energy Rating -amount of dissipation energy in joules (J)
Peak Current - value of the varistor peak current in amperes (A)
Max DC Voltage - varistor maximum DC voltage value in volts (V)
Max DC Current - varistor maximum DC current value in amperes (A)
Diameter - diameter of the varistor in millimeters (mm)
The following settings are common to all component type parameter dialogs:
Manufacturer - The name of the company that manufactures the component.
Part Number - The part number that uniquely identifies the component.
Click OK to add the custom capacitor to the library. The 
User mark will indicate the custom varistor in the component list.