When selecting power sources for welding, take into account technological and economic indicators. The choice of sources will ultimately be based on economic calculations, but this economic calculation will be performed from the set of sources that satisfy the first two criteria. Therefore, it is necessary to know about these two criteria.

The power source is considered to be technological if it provides:

- the arc stability (estimated by the coefficient of stability– К
_{У}); - the arc elasticity;
- the minimum level of spattering of the electrode metal.

The arc elasticity is the ability of a stable arc to burn without breaks in its elongation.