Previous in Forum: ac or dc   Next in Forum: Neutral tripping characteristic when circulating current happen(genset parallel)
Close

Comments Format:






Change Mode
Close

Subscribe to Discussion:

CR4 allows you to "subscribe" to a discussion
so that you can be notified of new comments to
the discussion via email.

Close

Rating Vote:







Add Vote
10 comments
Rate Comments: Nested
hithuanand
Power-User
India - Member - New Member Engineering Fields - Electrical Engineering - New Member

Join Date: Apr 2010
Location: Asia/India
Posts: 365
Good Answers: 1

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.
Register to Reply
Pathfinder Tags: capacitor farad Power Factor reactance
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Good Answers:

These comments received enough positive votes to make them "good answers".
Anonymous Poster
#1

Re: Capacitor value

05/07/2010 9:20 PM

11kv is very high voltage for a capacitor.
Register to Reply
dhayanandhan
Guru
Engineering Fields - Mechanical Engineering - New Member

Join Date: May 2008
Location: CHENNAI, TAMIL NADU, INDIA.
Posts: 1851
Good Answers: 65
#9
In reply to #1

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
Register to Reply
Tornado
Guru
Technical Fields - Technical Writing - New Member Engineering Fields - Piping Design Engineering - New Member

Join Date: May 2009
Location: Richland, WA, USA
Posts: 21017
Good Answers: 795
#2

Re: Capacitor value

05/07/2010 9:23 PM

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

__________________
 In vino veritas; in cervisia carmen; in aqua E. coli.
Register to Reply
dvmdsc
Guru
United States - Member - New Member

Join Date: Mar 2010
Location: In the pool because it is too hot.
Posts: 3054
Good Answers: 141
#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.

__________________
 Plenty of room here
Register to Reply
Anonymous Poster
#4
In reply to #3

Re: Capacitor value

05/07/2010 10:50 PM

Is there any capacitor which can deal with such high voltage (11kv)?
Register to Reply
3
msamad
Guru

Join Date: Feb 2009
Location: Houston, USA
Posts: 946
Good Answers: 244
#5
In reply to #4

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)

For additional help, see this link:

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

- MS

__________________
 "All my technical advices in this forum must be consulted with and approved by a local registered professional engineer before implementation" - Mohammed Samad (Linkedin Profile: http://www.linkedin.com/in/msamad)
Register to Reply Good Answer (Score 3)
No more Good Answers.
hithuanand
Power-User
India - Member - New Member Engineering Fields - Electrical Engineering - New Member

Join Date: Apr 2010
Location: Asia/India
Posts: 365
Good Answers: 1
#6
In reply to #5

Re: Capacitor value

05/08/2010 10:45 PM

Thank you everybody.
Register to Reply
pnaban
Guru

Join Date: Jun 2010
Location: srilanka
Posts: 2725
Good Answers: 5
#8
In reply to #5

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?.

__________________
 pnaban
Register to Reply Score 1 for Off Topic
hkian
Commentator

Join Date: Jan 2010
Posts: 73
Good Answers: 1
#7
In reply to #4

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...
Register to Reply
dhayanandhan
Guru
Engineering Fields - Mechanical Engineering - New Member

Join Date: May 2008
Location: CHENNAI, TAMIL NADU, INDIA.
Posts: 1851
Good Answers: 65
#10
In reply to #4

Re: Capacitor value

03/29/2013 5:45 AM

Dear Friend,

The Answer for your question is YES.

DHAYANANDHAN.S
Register to Reply
Register to Reply
Have a Different Question?
10 comments

Good Answers:

These comments received enough positive votes to make them "good answers".
Copy to Clipboard

Users who posted comments:

Anonymous Poster (2); dhayanandhan (2); dvmdsc (1); hithuanand (1); hkian (1); msamad (1); pnaban (1); Tornado (1)

Previous in Forum: ac or dc   Next in Forum: Neutral tripping characteristic when circulating current happen(genset parallel)

Advertisement

Got Something to Say?
Ask a Question
Start a Discussion

Search this Forum
Electrical Engineering:
Go

CR4 Sections
Aerospace
BioMech & BioMed
Chemical & Material Science
Civil Engineering
Communications & Electronics
Education and Engineering Careers
Electrical Engineering
General Discussion
Instrumentation
Manufacturing
Mechanical Engineering
New Technologies & Research
Software & Programming
Sustainable Engineering
Transportation

Site Directories
Forum Directory
Blog Directory
User Group Directory
RSS Feeds

CR4 Rules of Conduct
CR4 FAQ
Site Glossary

Who's Online (87 right now)
Show Members
Advertisement