Patent ID: 8232501

Claim:
A plasma arc power supply used in a plasma arc apparatus that processes a workpiece by forming a pilot arc between a main electrode and a nozzle electrode of the plasma arc apparatus and subsequently forming a main arc between the main electrode and the workpiece, the power supply comprising: N direct current power supply units each having positive and negative terminals, the terminals being connected to the main electrode and the workpiece, where N is an integer greater than or equal to 2; and a switch arranged between a first direct current power supply unit that is one of the N direct current power supply units and the workpiece, wherein the first direct current power supply unit is connected to cause the nozzle electrode to have an opposite polarity to the main electrode, and when the switch is open, the first direct current power supply unit supplies a small current between the main electrode and the nozzle electrode while forming a pilot arc between the main electrode and the nozzle electrode, after the pilot arc is formed, a second direct current power supply unit that is another one of the N direct current power supply units solely supplies a small current between the main electrode and the workpiece while forming a main arc between the main electrode and the workpiece, when a load current exceeding a small current region is set, the second direct current power supply unit increases the small current to a predetermined value, and when the current from the second direct current power supply unit reaches the predetermined value, the remaining direct current power supply units start supplying currents and a total output of the N direct current power supply units is used as the load current.