There are many types of welding machines and methods. Basically they fall under two main categories. CC & CV - Constant Current & Constant Voltage.
MMA welding - (Manual Metal Arc welding or just Stick welding) - using a flux coated welding rod - requires a constant current power source. It can use AC or DC type current.
Gas Metal Arc Welding - also called Metal Inert Gas (MIG) or Metal Active Gas (MAG) - this type is found in workshops and requires DC current with a constant voltage power source.
Flux cored Arc welding - Similar to MIG with a slight modifications.
Gas Tungsten Arc welding - Alloyed Tungsten electrode creates the heat required to fuse the materials. The arc is shielded by an inert gas to protect the electrode and the weld from the atmosphere.
There are two voltages in play here. They are the Closed and Open Circuit Voltages. When you are doing the welding the circuit is obviously
closed and the voltages are less. Depending on the electrode size they will vary between 20V to 30V. But the current can vary between 50A to 300A.
Open circuit voltage (OCV) is the voltage at the output terminals when the machine is on but no welding is done.
However, to start the arc you need a higher OCV - for safety reasons usually these are limited are 80 V for AC sources and 115 V for DC. This depends on the safety regulations in the country where it's used. Note some machines offer much higher strike voltages around 200V.
The IEC-60974 series documents the details if anyone is interested.
