Hopefully someone with PFC knowledge can help me out here.
A formula of mine is not coinciding with A sizing Capacitor chart from a local distributer. And I am curious why?

This Formula:
C = KVAR / (2 * pie * F * V^2) Translation: 2 times 3.14 times frequency times voltage squared.

Assume KVAR= 10.188, F= 60, and V= 480.
This formula should come out with an answer in Micro Farads.

The data sheet from a local distributor is saying a 10KVAR cap rating shoulds read/measure Min: 57uF--MAX: 66uF.

Can anyone clear this up for me?

 

Rereading this I thought...Should I post this in the Electronics Forum? I know it is a simple math problem but getting to the answer may be more in the electronics field than math? I know I did not include many details about how I came up with the 10.188 but that should be irrelevant.

 

A fast mental workout says the manufacturer 1s correct.
Where did you get the formula from?

 

I get 56.3 uf.

Look carefully: Is the sizing chart from the distributor or the manufacturer?
Motor quality has changed a lot in the last 20 years. A distributors chart might be way out of date.

 

If the the 10 kvar is delivered by a single capacitor @ 480V working then the equivalent capacitance would be ~115uF.

 

@t_n_k The title of the thread is about power factor correction for an inductive load, not total power delivered by a single capacitor...or am I missing something important?

Then I look at my math and see that I did not square the 480 volts.

Therefore, some doubt remains.
I hope we have been helpful in some way.

 

@t_n_k The title of the thread is about power factor correction for an inductive load, not total power delivered by a single capacitor...or am I missing something important?

Then I look at my math and see that I did not square the 480 volts.

Therefore, some doubt remains.
I hope we have been helpful in some way.

The OP hasn't presented the question with great clarity.
Irrespective of that, a capacitor with a specific kvar "value" will have a capacitance value commensurate with the nominal kvar, operating voltage & frequency. What else could one conclude?

 

Thanks. I was trying to draw a conclusion from the small scale work I do, and it doesn't stretch that far.

 

Hopefully someone with PFC knowledge can help me out here.
A formula of mine is not coinciding with A sizing Capacitor chart from a local distributer. And I am curious why?

This Formula:
C = KVAR / (2 * pie * F * V^2) Translation: 2 times 3.14 times frequency times voltage squared.

Assume KVAR= 10.188, F= 60, and V= 480.
This formula should come out with an answer in Micro Farads.

The data sheet from a local distributor is saying a 10KVAR cap rating shoulds read/measure Min: 57uF--MAX: 66uF.

Can anyone clear this up for me?

I get that a single cap needs to be 117 uF to have that reactive power under those conditions (i.e., same as t_n_k). What conditions does the data sheet apply to? I could envision it being intended to size a set of caps in a three phase system, for instance.

 

Thanks for the replies everybody!
I kept coming up with around 115 Micofarad also.
This is the manufacture datasheet.
It does specify 480V 60Hz 3 phase on the datasheet, so this is why then the formula I posted is for a single cap?
So how are they then coming up with the round abouts 56 Microfarads?
They must not be wired in parallel because i come up with 18 Microfarads?
They are wired in series parallel?

Or do you have to multiply the 480 x 1.73 before hand?

 

Sorry did the parallel calculation wrong. I calculated it for series capacitance.

 

This is the manufacture datasheet.
It does specify 480V 60Hz 3 phase on the datasheet, so this is why then the formula I posted is for a single cap?
So how are they then coming up with the round abouts 56 Microfarads?

Did you post a link to the data sheet?
Hard to comment unless one can view the manufacturer's information.
Even if the 10kvar is distributed across three phases the value of 56 uF remains a mystery.