Motor Starting Calculation
Motor Starting Calculation

Motor starting case studies

A motor starting case study for any given electrical network can be performed by reduced the network to a smaller equivalent network consisting of a source (generator / grid), the starting motor (largest motor), other large running motor and a lumped load.

This MS Excel based spread sheet is based on this concept and present a small model of electrical network that can be adapted for such motor starting case studies.

This is very helpful especially for quick checks as follows:

  1. What is the largest motor size that can be started with a given generator rating
  2. What should be the rating of the generator (or nos of generator operated in parallel) for a given load and largest motor size
  3. Knowing voltage drop during starting conditions for given motor details and hence deciding the key parameter during design (say max allowable starting current)
  4. Deciding the cable size / number of runs etc.

The spread sheet performs an iterative calculation based on pre-start load inputs and starting motor data. Detailed analysis may be performed with the help of available softwares.


  1. Motor starting analysis are generally performed for the largest motor connected to a switchboard.
  2. For worst case results, motor starting analysis are generally performed considering the weakest source.
  3. Considering the above two facts, any given electrical network, where a starting analysis of a motor is required, can be reduced to a simplified network consisting of a source (generator/s or grid), the starting motor (largest motor), the running motor/s (second largest motor/s or motor of same rating as the largest motor under study) and other loads lumped together.
  4. Modeling
    This spread sheet allows the user to model a given network as follows:

    1. Generator/s: The details of one generator shall be entered. If there are more than one generator of identical rating, these can be modeled simply by enter the number of generator in parallel.
    2. Grid: The details of grid shall be entered
    3. Transformer/s: The details of one transformer shall be entered. If there are more than one transformer of identical rating, these can be modeled simply by enter the number of transformer in parallel.
    4. The spread sheet considered either the “Generator/s” or the “Grid” supply for the motor starting analysis. The “source for the motor starting analysis” can be selected by the use via the drop down menu. The selection automatically simulates switching “ON” or “OFF” the respective source breaker.
    5. Starting Motor: The details of the largest motor connected to the switchboard shall be entered.
    6. Running Motor/s: The details of the second largest running motor/s (or motor of rating same as the starting motor) connected to the switchboard shall be entered. This model can also be utilized by the user to check the voltage drop at the terminals of any remote motor/s.
    7. Lumped Load: The details of the remaing load on the switchboard can be modeled as a lumped load. The % motor can be defined which shall be modeled as constant power load while remaining % of load shall be modeled as constant impedance load for the calculation.
    8. Error in data entry of the “voltage” input shall be highlighted, if bus voltages are much different from the generator terminal voltage input of transformer voltage ratio inputs.

The excel spreadsheet has 2 sheets as follows:

  • Sheet title “Preface” with notes explaining about the calculation spread sheet and the summary about the software and
  • Sheet title ” Motor starting calculation” where actual data entry and calculations can be performed
Software:Motor Starting Calculation
Developer:Hemant Kashikar
Size:104 Kb
Download:Right here | Get Download Updates | Get Technical articles
Motor Starting Calculation
Motor Starting Calculation

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Page edited by E.C. (Google).


  1. Vikram
    Jul 05, 2016

    Its an awesome workout and very useful.

  2. ANIL
    Feb 14, 2016

    Could not enter value generator voltage 6600 v for solo generator mode

  3. FELIX JR.
    Feb 14, 2016


  4. Boomi
    May 13, 2015

    Very much informative and I like all spreadsheets
    Thanks for uploading.

  5. Jason Buda
    Apr 21, 2015

    The excel spreadsheet downloaded just fine for me… It is very involved and I am looking forward to picking at it to fully understand how to use it. The introduction sheet seems very intuitive! Thanks for sharing!

  6. Abdulwahid
    Jan 15, 2015

    unable to download the excel sheets

  7. Rakesh Dhedhi
    Sep 11, 2014

    Dear Sir / Ma’am,
    First of all thanks for making such beautiful site for electrical world.

    In Electrical software, download file option it gives following errors while downloading file:
    1. By right click option : It saves html page instead of excel or other file.
    2. By : We’re sorry, the server encountered an unexpected error.

    I hope admin will rectify this problem asap.
    Thanking you in anticipation.

    With best Regards,
    Rakesh Dhedhi
    Electrical Engineer

  8. Denis Milton
    Aug 27, 2014

    Motor Starting Calculation-Rev1.xls

    We’re sorry, the server encountered an unexpected error.

    Aug 26, 2014


  10. Melvin
    Jul 16, 2014

    unable to download the excel sheets

  11. Alfredo Labung
    Mar 28, 2014

    keen to know more about articles, software, guides & lectures of EEP tech refs as well…

  12. Nitin
    Feb 21, 2014

    Not able to download excel sheets…plz help

  13. nandaarief
    Nov 19, 2013

    thanks a lot, its very helpfull

  14. saunak
    Sep 23, 2013

    This site is really excellent i m very thankfull…it can be change my life electrical engineering….
    thank you soo much eep.

  15. Ashraf
    Jul 25, 2013

    I am not able to download the excel sheet

  16. karthikeyan
    Apr 09, 2013

    hi guys.. i am fresher to engineering…
    i would like to learn how motor starting calculation is done.
    please send me some technical articles/books in this regard to y mail id (
    thanks in advance.

  17. WillG72
    Mar 02, 2013

    I cannot download either. I did as you advised about clearing the cache. When I click on ‘Download’, I am taken to a preview page called ‘Box’ and states that I need to login to it. I never heard of this and why do I need to login to some other site?

  18. munis.munnu
    Oct 29, 2012

    i am not able to download the excel sheet….

  19. natemp
    Jul 03, 2012

    The worksheet not producing resuts for the below combination (even though this is not praticle)
    Transformer for voltage rating 11/0.2kV
    All loads with 0.2kV
    V2 bus voltage 0.2kV

    Please advise how to over come this issue


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  21. mpsaxena2003
    Nov 01, 2011

    I have made a vba macro in MS Excel for Transformer Sizing .I want to upload it in this site. How i do it.

  22. ajay34
    Aug 17, 2011

    why i cant download.. Motor Starting Calculation…

    even i had log in

    • Edvard
      Aug 17, 2011

      Logout and clear the cache in your browser and then login again. It should work. There was some works and improvements on EEP, so try to clear your cache.


      • WillG72
        Mar 02, 2013

        Back again. —- I am new to this and my first time trying to download. I have tried to access other downloads and, apparently, I cannot download anything because it takes me to another website called ‘Box’ and I need to download again! Do I need to have a ‘Box’ account, also? If so, this should be noted and clarified on the very first download page. I feel stupid for not knowing how to do a simple download that I have signed up for. Please give me simple instructions that actually fit the program.

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