Inverter Power Source for MMA welding, 400Vac three-phase power supply for welding with coated electrodes.On the front panel a digital instrument display shows the operator a reading of the actual welding current for precise amperage settings.Hot Start and Arc Force are adjustable via two knobs on the front panel and the welding current s adjusted by one control knob.For your own safety, the Riland Arc 250G and 400G are equipped with the VRD system. The Voltage Reduction Device (whose acronym is: VRD) is a device used to decrease output voltage to a safe level when the welding source it is outside the welding cycle. Through this particular arrangement, when the arc is switched off, the open circuit voltage is reduced to only 25 V.