TWI Technology Briefing 410 - March 1990
M Amin
Scope
A linear voltage-current synergic control unit has previously been developed at The Welding Institute to regulate automatically the steady DC open arc MIG operation. Originally, the unit was designed to work with a versatile but high cost transistor controlled power source and then adapted to a low cost and more widely used thyristor controlled power source.
At present, a newly developed inverter controlled power source has become popular because it is small, light, efficient and relatively low cost. Therefore, to promote the wider use of synergic control technology, the control unit has been adapted and tested with an inverter controlled power source in this study.
Two techniques have been used to adapt the control unit to the inverter controlled power source. One uses the generalised 'reference voltage-output current' relationship to take account of the characteristics of the inverter controlled power source. An alternative approach uses the 'voltage feedback control' technique to accommodate the power source characteristics.
Main conclusions
- The synergic control system regulates the welding operation automatically and produces sound welds with both constant as well as modulated wire feed, for both mechanised and manual welding operations.
- There is no significant difference between the performances of the two control techniques.
Recommendations
The synergic control unit has been adapted and evaluated successfully with transistor, thyristor and inverter controlled power sources, for the regulation of steady DC open arc MIG welding. The control unit can now be used, as an 'add-on' unit, to control the power sources, especially for mechanised welding operations.
The use of the 'voltage feedback control' is preferable on the grounds of simplicity and versatility.
