Capacitor sizing for power factor correction

Commonly method for power factor correction using the capacitor to generate reactive power ( kVAR ) to reduce apparent power ( kVA ) form inductive load.

This time i want share a simple method to sizing our capacitor to improve power factor for induction motor and utility electricity.This method also can use for capacitor bank sizing.

Power factor correction is the one of famous topic for all electrical person at around the world.Many discussion and debate about how to sizing the capacitor for power factor correction.

How to sizing capacitor for power factor correction?

To properly sizing the amount of capacitor (kVAR) required to correct the lagging power factor,we  must have three (3)  important of information below:

  • kW (kilowatts)
  • Existing Power Factor ( % )
  • Desired Power Factor ( % )

From this information,now we can calculate the capacitor size for power factor correction.The formula to calculate the required kVAR is:

Factor from Table 1 below x kW = kVAR of capacitors required.

Calculation Example :

1 unit air-compressor ( 3 phase 415 VAC ) used an average of 90 kW with an existing power factor of 80%.The desired power factor is 95%. The factor value for this case is 0.421 to raise the power factor from 80% to 95% using table 1.

0.421 x 90 kW = 38 kVAR

So we need capacitor size 38 kVAR to get power factor 95% for 1 unit air-compressor 90 kW.

If working power (kW) or Present Power Factor are not known you can calculate from the following formulas to get the three basic pieces of information required to calculate kVAR.The best range for  desired power factor is around 95% until 100%.



  1. haitham hashim says:

    If I had known this site earlier when she entered the Faculty of Electrical Engineering, read the threads started by Mr. Admin and I become a better engineer, thank you, Mr. Adam

  2. Are pf and efficiency of motors given nameplate of all motors?.
    If no-load current is known(given in nameplate) can we estimate the size of capacitor required a) to start the motor (by reducing starting current)
    b) to correct pf?.

  3. Hi
    Nice explanation
    There is something similar explained for capacitor sizing

  4. hello, nice article!!! I am really impressed. Actually this is my first time reading your post. But I am very fascinated by the way you explained this simple method in sizing up a to improve power factor for induction motor and utility electricity. Thanks for sharing this information. Really good. I will be subscribing to your feed. Rest assured that I will read your future posts..

  5. BHARGAV says:

    dear sir,
    thanks for reply
    if i have a only motors HP ratting, then how i can know require KVA of capacitor??
    thanking yoy

    • no problem bro,
      do you mean for power factor correction for induction motor?
      follow this step :-
      1) Convert hp to kW;formula : 1 hp = 0.746 kW
      2) from kW,you convert to Ampere;formula : I = kW / volt x 1.73
      3) from ampere you can find the kVAR for power factor capacitor..for more detail please read my post about capacitor sizing for power factor.

  6. Muhammad Waqar says:

    Above calculation is for global compensation only when a PFI Panel is to be installed at site for whole load(s).

    Please BE CAREFUL when installing shunt capacitor with motors (sometimes called individual compensation). You should select the Kvar as per following formula:
    Qc (Kvar) = 0.9 x Io x Voltage (U) x 1.732
    Io is the no load current of a motor which shall be 20% to 30% of heavy motors.

    Muhammad Waqar
    Lahore Pakistan

  7. I got that I need a Supco Hard Start Kit Capacitor of 24???? I have a small common house freezer that does NOT already have any capacitor. I want to install one to help it get started. All I know is it is rated at 1/6th Horse Power or 124kW, 1.2 amp, 240volt on the sticker on the back of the unit, I do not know the efficiency percent etc. I found these equations difficult can anyone check over my answers for if what I got below is wrong or right. Or if you are interested to do the math and tell what i should get in capacitor size?

    I have included all my workings outer the math. New at this so not sure what I’m doing or if its right.

    Power Factor = 0.222


    number time by 1.73×Rated amps 1.2×motor voltage 240× power Factor 0.222

    kW = 1.73×1.2×240×0.222

    kW = 0.110

    kW = HP .124 x .746 / .84 as %age (a guess) motor efficiency

    kW = 0.110

    kVa = 1.73×1.2amp×240v/1000

    kVa = 0.49824

    Power Factor = kW .124(1/6th Horsepower) / kVa 0.49824

    Power Factor = 0.222
    PF 0.222 x kW 0.110 = 24kVAR???
    Answer = 24kVAR

  8. Hi therde colleagues, nice piece of writing and pleasant arguments commented here, I am reeally enjoying by

  9. Reduces Inner Bacterial and Fungal bacterial infections:
    Natural ACV contains many nutrients. It is free to use when contacting other Skype
    users, and expenses on $0.021 a minute when calling a landline.
    unique iPhone 5S cases recently posted..unique iPhone 5S casesMy Profile

  10. You can get this luxurious gadget in two colors black and white.
    But fortunately, the seems started to fade and grew more
    distant. The messaging formats will consist of the SMS (threaded view), MMS, Email, IM,
    Push E-mail.
    cool iPhone 5S cases recently iPhone 5S casesMy Profile

  11. The graphics are amazing and keep up to speed with current technologies and developments.
    It will certainly give you the best consumer experience and full fulfillment.

    This is a sister orchard to Boa Vista and is very small.
    unique iPhone 5S cases recently posted..unique iPhone 5S casesMy Profile

  12. I was wondering if you ever considered changing the page layout of your blog?
    Its very well written; I love what youve got
    to say. But maybe you could a little more in the way of content so people could connect with it better.
    Youve got an awful lot of text for only having one or 2 images.
    Maybe you could space it out better?
    nikon d700 recently d700My Profile

  13. If some one desires to be updated with newest technologies after that he
    must be pay a visit this site and be up
    to date everyday.
    weather the villages fl recently the villages flMy Profile

  14. Obtaining someone to begin a blog is easy. You could get began using a blog in
    a matter of minutes.
    Charli recently posted..CharliMy Profile

  15. You could possibly have heard about report article spinners.

    What’s short article spinning aand why do we need to have these rewriters?
    how to spin articles recently to spin articlesMy Profile

  16. Vous гédigez сontinuellement des postes fasciոants
    pornographique recently posted..pornographiqueMy Profile

  17. I know this site presents quality depending
    articles or reviews and additional information, is there any other web site which gives these data in
    red little Tikes trike recently little Tikes trikeMy Profile

  18. I’m not certain where you are getting your info, however
    good topic. I needs to spend some time learning more or understanding more.
    Thank you for magnificent information I was in
    search of this info for my mission.
    Dan recently posted..DanMy Profile

  19. I am regular reader, how are you everybody? This paragraph posted at this web site is
    actually pleasant.
    tennis college recruiting recently college recruitingMy Profile

  20. I like what you guys are up too. This sort of clever work and coverage!
    Keep up the good works guys I’ve added you guys to
    our blogroll.
    college golf recruiting recently golf recruitingMy Profile

  21. We’re a group of volunteers and opening a new scheme in our
    community. Your website offered us with valuable information to work on.
    You have done an impressive job and our whole
    community will be thankful to you.
    tennis scholarship recently scholarshipMy Profile

  22. There is certainly a lot to know about this topic.
    I like all of the points you have made.
    หางานพาร์ทไทม์ recently posted..หางานพาร์ทไทม์My Profile

  23. Your mode of explaining all in this article is in fact pleasant, every one be able to
    easily be aware of it, Thanks a lot. recently posted..ir4.comMy Profile

  24. I every time spent my half an hour to read this web
    site’s content everyday along with a cup of coffee.| recently Profile

  25. On tɦe other hand, thinking thwt there is absolutelƴ no hope for
    you to wwin him ƅack tɦeո yoou chances ɑre just that, ոo hope.

    It is marked with a waist ѕize that is less thawո 23 cm smkaller than the Һips or tthe breast measurement.
    A well-timed moan, for instance, cɑn actually add tο thhe sensuality of the moment.
    gbmack is the bomb recently posted..gbmack is the bombMy Profile


  1. [...] motor to reduce FLA..I used simple power factor calculation for electric motor from this post : sizing for capacitor power factor & power factor capacitor [...]

  2. [...] to excellent.How we measure the electrical efficiency?The answer is power factor.I discussed about how to sizing capacitor for  power factor correction on my last [...]

Speak Your Mind


CommentLuv badge