Once a stable arc with proper thermal equilibrium has been established, it is essential to maintain it so that welds of consistent quality can be achieved. Normally, it is not difficult to re-ignite a stable arc, if it goes off momentarily. Whereas thousands of volts may be required to initiate an arc in TIG welding machine (gas tungsten arc welding), it may require only tens or at the most hundreds of volts to reignite it.

Maintenance of an arc when ppr pipe cutter with an ac power source is rather a problem because the arc extinguishes every half cycle when the current is zero, that is, it will extinguish 100 times a second with a normal 50 hertz mains supply. For re-ignition the required voltage must be available at the time [...]