Single phase power factor controllers - do they exist?

Thread Starter

Just Another Sparky

Joined Dec 8, 2019
I'm trying to track down a power factor controller capable of operating on 120 volts single phase. 99% of the parts available seem to be made for 208-480 volts three phase. As I understand, a three phase power factor meter will not function correctly on single phase power (Current sensing is typically done on L1 and voltage input is taken across L2 and L3 if memory serves).

All I need is some kind of a solution to cut in and cut out some capacitors in response to changes in power factor. I've got some machines in the garage and the ancient motors in them exhibit horrific power factor under light loads (COS φ = 0.3-0.35). This means I end up paying for 3 times more energy than I am actually using.

My original plan was to just correct each machine individually in some fashion (easy), but then I got to thinking about all the other equipment that gets plugged and un-plugged down there from time to time and figured it might be worth a stab to just put together an "autovar" type system.

My question is: Is there an easy/cost effective way of going about this, either with store-bought components or home-brew circuitry, or should I just save myself the trouble and stick with the tried-and-true technique of installing an individual cap bank on the load side of the drum switch for each machine?

Last edited:


Joined Jul 18, 2013
You are probably not going to find a P.F.Controller for 1ph as mostly this would apply to residential installations and it is often not deemed necessary due to the lighter loads of a residential supply and the degree of saving against the cost of the units and installation costs.
The solution of installing the individual banks one each M/C is probably the most viable.
Just ensure the quality of the capacitors are up to the task.
The ideal is a P.F. meter which switches the caps in as needed.