With an inverter type welder, AC input current is rectified into DC output current.  Because of the high frequency and good heat efficiency, this type of welder is suitable for precision welding of electronics components.  The inverter welder offers three control modes:  constant voltage, constant current, or constant power. The voltage feedback function allows the welder to adjust to changes in the weld condition in real time, leading to stable, quality welds.  High speed repetitive welding makes this welder good for automated systems. 
 

With a linear DC welder, the electric current is directly controlled by a transistor.  This produces fast control speed and a controlled wave form.  With a high speed linear controller, this welder is suitable for welding of very small components or extremely fine wires.  The transistor welder offers three control modes:  constant voltage, constant current, or constant power.  The control modes make possible very dependable and consistent welds.  

The hybrid type battery spot welder possesses the high speed properties of a DC power supply, and the polarity switching function of an AC power supply.  The polarity of a high current is switched at high speed by a power transistor.  This type of welder is very good for battery tab welding, where different types of metals must be series welded.

 

With a capacitor discharge welder, electric energy is stored in a capacitor and discharged all at once.  Because a large current can be discharged all at once, this type is useful for welding highly conductive materials such as aluminum and copper.  Also because of the short welding duration, heat impact on surrounding material is minimized, making it useful for welding small sensitive components.

In a single phase AC welder, current is controlled by a thyrister, and operates at relatively low peak current.  This type of weld current is less affected by dirt or contamination at the weld.  Because the weld time can be adjusted more wide range, this type of welder is suitable for thick plates and copper wire.