Cost Effective Power Factor Correction

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kdubya

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One of our customers has a 83% - 85% lagging power factor at the service to his wood-drying kiln building. The information was obtained by a data logger connected to the line side of the main over a two month period. The building's electric load is six 5HP motors on VFD's, several 3HP circ. motors and a number of smaller motors and HID lighting. A sales rep would like to propose installing capacitors to raise the PF to 95%. I thought that 90% is ideal...anything greater may introduce leading PF.
--Is it cost effective to raise the PF by 5%
--Any thoughts on raising the PF to 95%
Thanks
 
zog

zog

Senior Member
Location
Charlotte, NC
kdubya said:
One of our customers has a 83% - 85% lagging power factor at the service to his wood-drying kiln building. The information was obtained by a data logger connected to the line side of the main over a two month period. The building's electric load is six 5HP motors on VFD's, several 3HP circ. motors and a number of smaller motors and HID lighting. A sales rep would like to propose installing capacitors to raise the PF to 95%. I thought that 90% is ideal...anything greater may introduce leading PF.
--Is it cost effective to raise the PF by 5%
--Any thoughts on raising the PF to 95%
Thanks
Click to expand...

Is he paying a PF penalty?
 
K

kdubya

Member
The correction numbers were calculated by a rep from a reputable manufacturer.
No, it's not one of those "black boxes" that we see peddled from time to time.
 
Jraef

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
DON'T install capacitors on a system feeding multiple VFDs and electronic (SMPS) ballasts without knowing what you are doing and engineering a complete system including reactors. You will hasten the death of the VFDs. Then whatever micro savings the caps provide (if any) will be more than eaten up by losses in the reactor(s). Waste of effort.

Something smells fishy here. If the majority of the load is running off of VFDs, the displacement PF they create is virtually nil; usually .95 or better. Same for the HID ballasts. Both will create distortion PF, but that will not affect the utility kVAR meter and capacitors alone will not necessarily correct it. In fact, they may make it worse if a resonant circuit ends up getting created.

But it's all moot anyway if the PoCo is not assessing PF penalties. The savings from correcting to .95 will be negligent at best as the others have said. Someone is trying to sell you a vial of snake oil, reputable or not.
 
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