Which power source type has a relatively flat volt-amp curve?

Which power source type has a relatively flat volt-amp curve?

• A. Constant Voltage machine
• B. Constant Current machine
• C. AC transformer
• D. DC inverter

Answer: (A)

A constant voltage power source keeps the arc voltage essentially the same as you change the welding current. Because the voltage stays nearly constant while current varies, the volt-amp (V-I) relationship appears as a flat, horizontal line. This flatness is what’s being tested: it shows that the machine regulates voltage rather than current, providing a stable arc length and consistent arc characteristics as you adjust current. If the machine were constant current, it would hold the current steady and let the voltage swing up or down to maintain that current, producing a V-I curve that isn’t flat. An AC transformer or a DC inverter can deliver welding power, but they aren’t defined by a flat volt-amp curve unless they’re configured specifically to regulate voltage; the key concept here is the voltage-regulating behavior that keeps the arc voltage constant.

A constant voltage power source keeps the arc voltage essentially the same as you change the welding current. Because the voltage stays nearly constant while current varies, the volt-amp (V-I) relationship appears as a flat, horizontal line. This flatness is what’s being tested: it shows that the machine regulates voltage rather than current, providing a stable arc length and consistent arc characteristics as you adjust current.

If the machine were constant current, it would hold the current steady and let the voltage swing up or down to maintain that current, producing a V-I curve that isn’t flat. An AC transformer or a DC inverter can deliver welding power, but they aren’t defined by a flat volt-amp curve unless they’re configured specifically to regulate voltage; the key concept here is the voltage-regulating behavior that keeps the arc voltage constant.