Power Factor for Lighting Panel

[timm333]

We take into account the low power-factor of inductive loads (motors) for sizing the capacitors for power-factor improvement.

What about non-motor loads like transformers, ballasts of lighting, welding machines, etc? Should we take into account the low power factor of these loads for capacitor sizing, or can we assume the power factor of all non-motor loads equal to 1?

 

[templdl]

1ph or 3ph?

 

[timm333]

The motor loads are all 3-phase. The distribution/lighting transformers are 3-phase, but the loads on the transformers (ballast of lighting, welding receptacles, etc) are single phase.

 

[templdl]

You are going to have to figure what your power factor is based upon what you loads are. The, if you want to add PFCCs you also must consider what your going to do when the loads are turned of where you may end up with a positive PF which is not good with PFCCs still connected.

 

[timm333]

The capcitors are in automatic steps. When some loads are off, less capacitance will be conncetd in the circuit. When more loads are on, more capacitance will be connected. It will prevent the power factor to exceed 1.

Shall I size the capacitors based on only the motor loads, or other inductive loads (transformer, welding machine, lighting ballast) as well?

 

[Jraef]

If the lighting is incandescent (ha ha ha...) then the PF would be 1.0. Anything with an electronic balast, which now is essentially everything, will have both a diplacement power factor and a distortion power factor, but the dirty little secret is that when they mfrsa sell them, they only list the displacement PF, not the distortion, because that would make them look bad However, ading PFCCs to circuits with non-linear loads is something to be done VERY carefully, because the PFC capacitors can interract with the electronic loads to create resonnance and you can get yourself in serious doodoo. I'm not a big fan of automatic bulk PF correction systemes for that reason.

For the most part, if you just correct the lagging PF created by induction motors, that is usually sufficient to take care of the penalties and that can be done by connecting PFCCs behind each motor starter, so they ONLY come on when the motor does.