Power Factor Correction Capacitors

Timeismoney08

Member
Join Date
Jul 2012
Location
United States
Posts
312
Hello,

I was just curious if a PF correction capacitor is ever used with a VFD install?

Have any of you ever needed to add a PF correction capacitor in any of your builds?



Thank you!
 
Out of pure interest, how were you 'bit'?

On one occasion, I was commissioning a panel with a handful of VFDs and a couple of servos. The servo motion would occasionally act erratic. After much time scratching heads and thinking that it was a tuning problem, I noticed the h/w designer had not designed in line reactors for the VFDs or Servos. I asked the electrician to rummage in their bone yard and install some in the new panel and the erratic behavior disappeared (or never again showed up).
 
Input reactors stop drive noise from contaminating the supply.
Output reactor reduce the noise on the motor cable and reduce the chance of crosstalk to other cables.
 
PFC is not needed with a VFD. With a large amount of VFD's in an industrial plant, you may need to look at a harmonic filter.

As stated above, input reactors mitigate some of the noise and harmonics that are sent on the line feeding the VFD. Output reactors are to smooth out the pulsed voltage that is created from the SCR's firing. They are also used to stop the reflected voltage spikes that are created with long leads from the VFD to the motor.
 

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