# The importance of power factor in inverter welding power sources

Power factor (PF) provides a measurement of a power source’s efficiency in exploiting the energy provided by the AC mains supply.

A system with unity power factor (PF = 1) is able to exploit all the energy delivered by the mains supply, while a system with a PF of 0.65 can only exploit 65% of it. As a practical example, take two welding power sources performing exactly the same work; one has a PF=1 and the other has a PF=0.65. If the power source with PF=1 needs to draw 10 A from the mains supply, the other power source with PF=0.65 will need to draw 15 A in order to generate an arc of exactly the same power.

## Power Factor is not (the same as) Cosφ

There is a fundamental difference between the concepts of Cosφ and power factor, though the two are frequently confused. Cosφ only measures part of an appliance’s power draw. Power factor (PF) is the only parameter that takes into consideration all the components of reactive power.