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Power-User

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Capacitor Bank Rating in Farad

07/20/2013 6:04 AM

How can we relate capacitor bank's kVAR ratings with farad

Simply

1kVAR= ?? farad

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#1

Re: Capacitor bank rating in farad

07/20/2013 10:14 AM

There are About 27,600 results on the web.

Try a simple search.

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#2

Re: Capacitor bank rating in farad

07/20/2013 10:18 AM

VARs are a unit of reactive power, farads are the unit of capacitance used inside of the VAR formula. So if all you know is one of those two values, you cannot determine one or the other. You will need system voltage and frequency.

...and a calculator.

VARs = V²/ Xc, or = 2*phi*f*C

V = system voltage

f = system frequency in hertz

Xc = capactive reactance

phi = 3.1416

C = capacitance, farad 

Xc=1/(2*3.14*f*C)

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#3

Re: Capacitor Bank Rating in Farad

07/21/2013 1:47 AM

To find out Farad or Microfarad, you shall also define following:

1. System:1 phase or 3 phase

2. Service Voltage

3. System Frequency.

For example for 3 phase system, at 415V line voltage and 50Hz system frequency, to produce 1kVAR of Capacitive Reactance we require 3 Numbers of 11Micro farad (0.000011Farad) capacitors in delta connection. Voltage rating of each capacitors shall be at least 415V.

Calculations are:

Xc (capacitive reactance) = 1/2ΠfC (Π = 22/7, f = 50 Hz, C =0.000011 F)

= 298.29 Ohms

Capacitive Power = 1.732*415*415/298.29

= 1000 VAR

= 1 kVAR

Similarly one can calculate capacitance at any voltage and frequency.

For example at new 3 phase line voltage = V volts And Frequency = F Hz, Capacitance for 1kVAR will be = 0.000011*(415/V)2*(50/F)

Regards,

Ramesh

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#4

Re: Capacitor Bank Rating in Farad

07/21/2013 4:10 AM

You cannot find a direct relation between kVAr and Farad. The higher the voltage the lower value capacitor will result the same kVAr value. The grid works as an inductive load. Its impedance XL. You have to install the same value capacitive impedance XC.

XLGrid = XCBank

In this case the capacitor bank will fully compensate the power factor. It's a sort of resonance.

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#5

Re: Capacitor Bank Rating in Farad

07/21/2013 3:57 PM

Guys, stop answering this guy he says he is a graduated engineer in electrical working as an electrical design engineer in the construction field. He has been told enough times to perform simple internet or CR4 site searches first.

This is a discussion forum not a free education site for the plain lazy, especially when the questions are of a transmission or distribution level (high voltage = very dangerous).

Muthuvel, have you considered taking a proper power generation and distribution course rather than asking us?

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#6

Re: Capacitor Bank Rating in Farad

07/21/2013 6:58 PM

If I can only discuss things that I know, and not can ask about things I don't know, then I won't stay here any longer.

Things I know, I don't have to discuss, because I know them already.

I come here to learn and to help other people.

I don't have a problem to share my information with people who

  • - have no time to take a course about the their unsolved question
  • - have no money to take that course
  • - have only a small problem and don't want to take the complete course
  • - have examined their problem and ask a second opinion from other members.

And I don't think people are helped just by telling them to google their problem.

I'm sure they already did some research on google before they come here.

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#7
In reply to #6

Re: Capacitor Bank Rating in Farad

07/21/2013 8:34 PM

If this is directed at my comment (which I think it is), firstly thank you for being the first to ask a very valid question I hoped someone would ask.

Secondly, have a look at the numerous previous posts by Muthuvel to get an idea of where I am coming from as an actual power and transmission Engineer and long time CR4 user. This is directed at a number of people on CR4 (not just Muthuvel).

At some point questions stop being general interest and start becoming potentially dangerous 'homework-like' spam, especially when most if not all can be answered with a simple internet search he obviously did not bother to perform (as we have mentioned to him and others time and time again). He says he is a graduate Engineer, he should know better.

Learning is all well and good and encouraged by most of us here, but trying to teach yourself transmission and distribution theory by asking us simple questions instead of performing basic internet searches yourself or taking a proper course is just plain lazy, potentially dangerous and NOT (in my opinion) what CR4 is intended for.

I don't think we would be having this conversation if this was a medical discussion site and he was a graduate Doctor, but is high voltage specification and design any less dangerous?

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#8
In reply to #7

Re: Capacitor Bank Rating in Farad

07/22/2013 4:37 AM
Re: Capacitor Bank Rating in Farad
After researching Muthuvel's questions history, it does indeed makes me doubt about his engineering capacities and you are right that it tends to wards homework-like spam.

You have a good point about the involved hazard, but if you call yourself an engineer, I hope most of us act like a bonus pater familias, and know to judge the dangers they are in.

Finally, a word of thank to you, jack of all trades, and all the others who share their knowledge in this forum.

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#9
In reply to #8

Re: Capacitor Bank Rating in Farad

07/22/2013 3:47 PM

I hope most of us act like a bonus pater familias, and know to judge the dangers they are in.

As an Engineer, ethics are ever present when we answer (or fail to answer) questions posted on CR4. Some don't understand this sometimes, and often we don't clearly explain our reasons for not answering the question properly or at all.

Finally, a word of thank to you, jack of all trades, and all the others who share their knowledge in this forum.

We're here to help and learn but sometimes rather than answering the question completely we judge links, short answers or 'tough love' responses to be the most appropriate.

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#10

Re: Capacitor Bank Rating in Farad

09/03/2013 4:29 AM

Finally I got the Answer

  • Capacitor current(Amps)=Icap= (Reactive power/Nominal voltage)=Q/E.
  • Reactance across the capacitor Xc=E/Icap=(1/2∏f C)
  • f is the frequency So C=(1/2∏f Xc)
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