2-phase loading in 3-phase circuit

[hkharmonic]

Dear Friend,

 

We have conducted an energy audit to a 2-phase loading which was supplied by a 3-phase circuit (Phase R & . We found that the power factor with both the leading and lagging signs for the phases. Why?

 

Since we're not often work with the 2-phase loading, so would the expert here can give me some advise on how's the 2-phase loading works ? i.e. power factor, current

 

Thanks,

 

HK

[marke]

Hello hkharmonic

 

Welcome to the forum.

 

If your two phase load is connected to two phases only, (ie two wires - no neutral) it is actually a single phase load across two phases. You treat it exactly like a single phase load. If you reference neutral in your measurements, you will have very strange readings due to the neutral reference.

 

Provided that you measurment equipement cna withstand 400 volt on the voltage input, connect it across the two phases rather than phase to neutral and you will get the correct measurement.

For correction, connect a single capacitor across the two phases.

 

Best regards,

[hkharmonic]

Hello Mark,

 

Thanks for your advise. For power factor correction, 3-phase capacitors (Ph-R, Y & were connected to the system. Will it function the same as to connect across only 2-phases ?

 

For the existing 3-phase PFC, any bad effect ? Will it waste the phase of capacitor without load connected ?

 

Best regards,

 

HK

[marke]

Hello hkharmonic

 

Three phase power factor correction will not correct this two phase load. The only way to correct this is by that addition of a single 400V rated capacitor across the load.

This load will not affect the three phase correction, but it will show as a total imbalance in power factor and you could increase the penalty by going into a lead power factor on one phase.

 

Best regards,

[hkharmonic]

Dear Mark,

 

It's poor that for the imbalance power factor. The system I think exactly has the problem you mentioned. But, why the total imbalance in power factor will appears? Is it because the phase-Y without load connected overcompensated by capacitor ?

 

Apart from the penalty for the lead power factor on one phase, will the power factor can be improved on the other two phases ? Beacuse there is no penalty for the power factor in leading sign in HK.

 

Best regards,

 

HK

[marke]

Hello hkharmonic

 

You are trying to correct an unbalanced load with a balanced correction method. The result will always be unbalanced. A leading power factor is just as bad as a lagging power factor, in fact it is often worse so I am surprised that you would not pay a penalty.

I would not recommend trying to correct with a three phase capacitor.

 

Best regards,