# Power Factor - What is it a characteristic of?

I always thought it was a characteristic of a powered device, rather than the power source.

A generator (whether it's a station or a small petrol powered one) does not have a power factor. I've been told that the power source has a PF.

Is this correct? Does the PF change depending on the load (type of device)?

• Quite simply you are forgetting that real life, all sources work as loads as well. – Aron Jan 27 '16 at 11:17
• It would be best to say that it is a characteristic of a device. Power factor correction can occur at just about any point in the system. – Sean Boddy Jan 30 '16 at 20:13

## 2 Answers

Yes, power factor is a characteristic of a load and how close it is to being purely resistive (current and voltage in phase). Power factor correction is generally a feature of a load (a computer, lighting system, etc.) that helps bring that load's current and voltage into phase alignment.

• A source can have an impedance that requires power factor correction - it's all about obtaining maximum power transfer. – Andy aka Jan 27 '16 at 8:55

A power source can have a significant impedance that can make power factor correction of a resistive load a possibility. For example if the output impedance of the generator is net inductive (the most likely situation) then to give the load maximum power a capacitor in series is used to counter the inductive impedance that would otherwise drop a few volts.

It's called obtaining maximum power transfer and IS related to the impedance of the source. See the diagram below: - The source has loss Rs and series inductance Xs. The load has a capacitance placed in series that totally cancels the inductive reactance and on the right you are left just with just the equivalent circuit.

This is power factor correction of a source rather than a load.