Electrical Troubleshooting Quiz, June 28, 2011

June 28, 2011
As part of a green initiative, your division VP hired a special team to "clean up the power factor" at every plant

As part of a green initiative, your division VP hired a special team to "clean up the power factor" at every plant. Your plant was the first on the list. Because you weren't involved in the actual work, you requested "as-built" drawings. The VP said those drawings were not in the budget and were not going to happen.

While this lack of documentation is bad enough, you have a more pressing problem. Since this team finished and left, you've had a rise in trouble calls all over the plant. The maintenance department is buried in repairs and repeat repairs. What probably happened, and how do you solve it?

Correcting power factor (PF) at the service eliminates the low PF rate penalty. To reduce your actual electrical consumption, you must correct PF at each load. But never install PF correction capacitors at a motor with a VFD, because doing so creates power quality problems and leads to failure of the VFD and motor. To correct for low PF at a VFD, simply upgrade to a newer VFD that's PF-corrected. It will also be harmonics-mitigated.

The fix for this situation is to remove the local PF capacitor(s) at each motor and upgrade to PF-corrected VFDs.

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