Main Contactor for MIG Welders, TIG Welders and Plasma Cutters. 12 Amp
They typically come as 24V AC and 24V DC in your machine but other voltages are available.
This size of contactor is usually good for machines up to 130 amps output
There will be three main contacts on the top of the contactor L1/L2/L3 these are for the windings to your transformer. The last contact comes in normally closed (NC) or normally open (NO) and these are generally used as auxiliaries in you equipment.