Arc Welding Machine -- MMA/TIG/SMAW/GTAW Welding Machines
MMA process use drooping characteristic power source and consumable electrodes which produces arc by scratching the electrode with the job forming a short circuit. It is only when the short circuit is broken, arc is formed and the main welding current starts flowing. Welding takes place as the electrode gets fused with the job under the cover of the slag. In case of TIG, arc starts between tungsten electrode (non-consumable) and the job under the cover of inert gas. Arc is started by scratching the tungsten electrode with the job or using a high frequency unit which initiates the arc between the tungsten electrode and the job.
Diode based power sources are the basic type arc welding power source used for MMA/TIG applications. Current control is achieved through saturable core reactor. Very reliable power source but not recommended for radiographic welding application as there is no dependable feedback for maintaining the output current constant due to fluctuation of input supply or change in load. Power factor is poor for these power sources.
Thyristorised power sources have current feedback control which maintains the set output current constant. There can be many welding features such as up slope, down slope, pulsing, etc. which can be incorporated in this type of power source. Efficiency and power factor of these machines are better than diode based machines.
Inverterised Welding machines are manufactured using switching devices such as IGBT (Insulated Gate Bipolar Transistor) MOSFET etc. This makes the power source very compact in size, very efficient and best in power factor. These power sources are incorporated with digital technology such as DSP etc. Fully programmable machines are available under this category.
A power source which can be used as Alternating OR Direct current power source with high frequency and programmable welding features. AC TIG is used for Aluminium Welding. Thyristorised or inverterised power sources are available with AC/DC characteristics. Welding transformers (AC) with DC suppressor, High frequency unit and TIG torch is used as AC TIG welding machine for Aluminium Welding applications. But this cannot weld precision jobs.