# when would you say it is a good idea to install a capacitor bank



## don_resqcapt19 (Jul 18, 2010)

You really need to look at where the utility starts charging a penalty for low power factor. There is very little savings by correcting the power factor if there is no PF penalty.


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## billymac93 (Apr 4, 2015)

Don, you nailed it! Capacitor banks, even when needed, are expensive and the ROI (return on investment may be years) The first thing to do is check with the local power authority to find out what the penalty is and when does it kick in. A check of the facility's utility bills will outline the actual cost. Try to get a years worth of bills to show any peaks/dips associated with weather extremes and production slowdowns/overtime etc. Once the cost of NOT having a capacitor bank is determined, one can explore the investments.
BillyMac93


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## telsa (May 22, 2015)

The typical, rule of thumb, for adding reactive power is that the client's power factor must be sliding below .80.

The reason for the sur-charge is that the Poco is compelled to size any Service based upon true power consumed -- divided by the power factor.

This means that the conductors, towers, transformers -- the works -- all the way back to the synchronous alternator have to be upsized.

Now you're talking really big money.

&&&&&&

This is such a big issue when major blocks of power are involved that the Poco's install their own reactive power components.

Traditionally they built synchronous capacitors. { Think of a synchronous motor that runs virtually no load -- but has its salient poles over excited to generate astounding amounts of reactive power. }

These days, the industry has hugely shifted over towards solid state power electronics and banks of capacitors. Such reactive power can also be pad mounted -- look to see 'big boxes' mounted right next to conventional transformers.

I've never heard of ANY utility popping a customer with a power factor above .90.

&&&&

VFD's have hugely reduced the issue. For all that the Poco 'sees' is the rectifying circuit. These have very high power factors. ( not being constructed out of inductors )

Indeed, one ought to first consider installing VFDs at every single significant motor load -- long before fiddling with reactive power adjustments.


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## Mshea (Jan 17, 2011)

I might add when the bad power factor overheats your service equipment.


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