How is current controlled in an AC inverter type?

In the AC inverter type, welding current is controlled by changing the pulse-width using a semi-conductor called IGBT.This control is called PWM (Pulse Width Modulation) control.Since the output from the welding power source is an alternating current of about 50 – 200Hz, a regular single-phase alternating current welding transformer can be used.
The feedback control to keep the weld current constant is called constant current control.