Capacitor on MCC with VFD

[Ron11]

Hello All,

I have an MCC 453 that has capacitors placed to help with power factor correction. On the same bus, there is a VFD present as well. Would anyone happen to know if the VFD could potentially affect the CAPS. Please share your thoughts

Thanks

 

[jraef]

Potentially, yes. It can actually go both ways; the VFD harmonics may affect the caps and the caps may affect the VFD. But beyond the concept of potentially, there are way too many variables to consider for getting an absolute determination over a forum posting., at least in my opinion.

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[Ron11]

Thank you Jraef. I was thinking of Harmonics as well but I guess I need to support the argument and not just make a bare statement. Do you have any other recommendations material wise to read(IEEE papers etc) that could help me support my stance that VFD harmonics in essence may affect the Capacitors.Appreciate the help

 

[RRaghunath]

Ron11,
The following is from IEEE Red Book:

"Harmonic problems. Symptoms of harmonic problems include blown power factor correction capacitor fuses, a reduction in plant power factor, motor and transformer heating and/or failure, and possibly unexplainable operation malfunctions of process controls, especially timing problems in electronic equipment. Typical causes of harmonic problems include the application of power electronics and other solid-state power control devices for plant processes combined with power factor correction capacitors, creating harmonic resonance situations."

Trust you will find it helpful.

 

[Ron11]

Thank You raghun. That helps. What would you think would be a possible solution to rectify such a problem?

 

[RRaghunath]

I can think of two actions:
1. De-Tuned (that won't allow other than fundamental component to pass to the capacitors) PFC capacitor banks and
2. Harmonic filters on the input side of VFDs or Low harmonic (with active front-end) VFDs