The distance current travels to make resistance-spot welds determines the amount of impedance, resistance to
current flow in the circuit. The longer the current path, the higher the impedance or power loss, in the circuit. In
multiple-direct spot-welding machines, which use weld guns with large throats, current paths are long; setups have
high impedances that require large transformers. Throat depth on these machines is typically 24 to 36 inches. The
deeper the throat, the higher the power loss and the larger and more costly the transformer.