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In the Forum: Audio Discussions
In the Thread: It’s mad, mad, mad... electricity.

Post Subject: PFC correctionPosted by JOHNR on: 12/1/2015

PFC is a function of adding Xc using capacitors to bring the current in the circuit downwards.
What you have is an inductive load giving a lagging PF eg a simple motor gives a PF of 0.85.
Thus the inductive element can be manipulated to bring it from lagging to leading. The economic target is 95%.

If you step back from the needs of an audio system, if applied properly, the current in a large supply network can be reduced quite considerably. In fact above certain loads, your power company will insist on implementing PFC.

The best way to observe this at home is to connect a clamp on meter to the line side of the supply and read off the current. For the purposes of this test, assume 10 amps.
Now add an 8uF capacitor, motor run type anywhere convenient, oil filled for cool running and watch the 10 amps go down to 8 amps.
Add a second cap and watch it go down to 6 amps. By adding more caps a point will be reached when the current increases. The PF will now be leading which is not good. Back off and aim for a 10% current reduction.

An example of this is if you have push pull amp, any technology will do.
Equip the socket with an 8uF cap and the sound will improve. Adding a second one may also help but be careful as the cap draws current.

It is not trickery, it is engineering. It is not done on small loads because the capacitive bank needs to be connected according to the load. You cannot leave it in because you will have to pay for the energy usage. In the case of the PP example, you turn on the amp then turn on the cap.

John

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