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# Capacitor value

05/07/2010 9:02 PM

Can anyone help me in finding the value of capacitor to be connected to a 11kv supply if we know the power factor? Please explain with formulas if you know.

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Anonymous Poster
#1

### Re: Capacitor value

05/07/2010 9:20 PM

11kv is very high voltage for a capacitor.

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#9

### Re: Capacitor value

03/29/2013 5:44 AM

Dear Friend,

CAPACITORS can be used even for 11 KV or 33 KV also

DHAYANANDHAN.S

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#2

### Re: Capacitor value

05/07/2010 9:23 PM

Not unless you know the kW (or MW) involved.

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#3

### Re: Capacitor value

05/07/2010 9:48 PM

When you know your reactive power:

Retro back P= U2 (square)/Z >>> Z = U2 (square)/P

Z = 1/ (omega)*C >< omega = 2 pi*f

C = 1/ (omega*Z)

>> work this to the power formula above.

(I'm becoming crazy, not able to put anything in this window that looks good enough) IMPORTANT:

you will know what capacitor(s) value to use. Beware of the power - and heat dissipation -

the bank has to be able to handle the current too.

And be of prime quality dielectricum for that high voltage!!!!

I never saw one, but others can fill me in.

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Anonymous Poster
#4

### Re: Capacitor value

05/07/2010 10:50 PM

Is there any capacitor which can deal with such high voltage (11kv)?

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#5

### Re: Capacitor value

05/07/2010 11:11 PM

Additional data is required to find it. Here is a generic calculation:

Let's assume these input data,

The total load in KW = kw

Initial power factor = pf1

The target power factor = pf2

System Voltage in KV = V

System frequency = f

For power factor improvement, pf2 shall be greater than pf1 (pf2 value closer to 1)

Calculation:

The initial KVAR, kvar1 = sqrt{(kw/pf1)2 - (kw)2}

The target KVAR, kvar2 = sqrt{(kw/pf2)2 - (kw)2}

Since pf2 > pf1, kvar1 > kvar 2

To improve power factor from pf1 to pf2, the required KVAR of the capacitor, kvar3 = kvar1 – kvar2

Again assuming it is a 3 phase system and the capacitors to be connected in Y, the required capacitor/phase, kvar = kvar3/3

Phase to neutral voltage vn = V/1.732

The required capacitive reactance Xc = (vn)2/(kvar x 1000) ohm

The required capacitor is C (in μf), then

Xc = 1/(2 x PI x f x C) (PI = 3.14)

C = 1/(2 x PI x f x Xc) μf (micro-farads)

http://www.powerstudies.com/articles/PowerFactorBasics.pdf

- MS

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#6

### Re: Capacitor value

05/08/2010 10:45 PM

Thank you everybody.

Guru

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#8

### Re: Capacitor value

10/13/2012 11:49 PM

can you give a table or chart to select size of capacitor for a)power factor correction b)motor starting by shunt capacitor method-for various kw and rpm of 3phase induction motors?.

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#7

### Re: Capacitor value

05/09/2010 6:28 PM

yes, there are capacitors for that... you just have to know the insulation as well as the bushing insulation level of your capacitor.. in our system we have, (23kV/sqrt(3)) capacitors installed...

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#10

### Re: Capacitor value

03/29/2013 5:45 AM

Dear Friend,

DHAYANANDHAN.S

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