Main arc ignition device and main arc ignition control method of plasma cutting machine

A main arc ignition device of a plasma cutting machine, comprising:

• gas supply means provided with gas switching means which switches at least either a gas flow rate or gas pressure so as to supply a plasma torch with a plasma gas at least either at a lower flow rate or at lower gas pressure as compared with a flow rate and gas pressure of the plasma gas at a time of cutting a work, before or immediately after starting arc;
• a pilot current circuit which supplies a pilot current to said nozzle from a plasma power supply when pilot arc is formed between an electrode and a nozzle of said plasma torch, at a time of starting the arc;
• a main current circuit which supplies a main current to main arc from said plasma power supply on forming the main arc between said electrode and the work, at the time of cutting the work;
• a main current detector which is provided at said main current circuit connected to said work, and detects the main current;
• and
• a semiconductor switch which is provided at said pilot current circuit connected to said nozzle, and interrupts the pilot current after said main current detector detects the main current.