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# Motor Starting Calculation (MS Excel Spreadsheet)

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## Motor starting case studies

A motor starting case study for any given electrical network can be performed by reducing the network to a smaller equivalent network consisting of a source (generator/grid), the starting motor (largest motor), another large running motor, and a lumped load. This MS Excel-based spreadsheet is based on this concept and presents a small model of an 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 spreadsheet performs an iterative calculation based on pre-start load inputs and starting motor data. The detailed analysis may be performed with the help of available software.

### Notes:

1. Motor starting analyses are generally performed for the largest motor connected to a switchboard.
2. For worst-case results, motor starting analyses 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 the same rating as the largest motor understudy) and other loads lumped together.
4. Modeling
This spreadsheet allows the user to model a given network as follows:

1. Generator/s: The details of one generator shall be entered. If there is more than one generator of identical rating, these can be modeled simply by entering the number of the generator in parallel.
2. Grid: The details of the grid shall be entered
3. Transformer/s: The details of one transformer shall be entered. If there is more than one transformer of identical rating, these can be modeled simply by entering the number of the transformer in parallel.
4. The spreadsheet considered either the “Generator/s” or the “Grid” supply for the motor starting the analysis. The “source for the motor starting analysis” can be selected 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 remaining 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 the 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 the calculation spreadsheet 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 Version: 1.0 Developer: Hemant Kashikar Size: 104 Kb Price: – Download: Here 🔗 (Get Premium Membership) | Video Courses | Download Updates

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1. Ram Prakash Sharma
Sep 11, 2019

Service provider

2. Fairoz Ahamed
Sep 02, 2019

Dear Sir,

3. Durgaiah Sangepu
Sep 02, 2019

This excel is password protected. Can u share the password to open this file.

4. RatnaKumar
Jul 18, 2019

Kindly send sample sheets.

5. Alpha king
Feb 20, 2019

Good souces!Thanks!

6. Khaled Ellithy
Jan 25, 2018

Thanks; Excellent for VDIP due to large motor starting;

7. Khaled Ellithy
Jan 25, 2018

Thanks to you all. I have got a lot of useful materials in power systems area for my students

Professor
Ellithy

8. Musse Mohamud Ahmed
Jan 05, 2018

Very good arrangements Guys, thank you very much.

9. bhavin patel
Dec 10, 2016

dear sir
can u please send me a detail example for the above excel sheet

10. Vikram
Jul 05, 2016

Its an awesome workout and very useful.

11. ANIL
Feb 14, 2016

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

• PIERO VERCELLINO
Mar 30, 2019

Dear Sirs,
many thanks to share your knowledge
On excel file i can’t change selection from main grid to generator grid (generator ON grid OFF)

Thanks

Piero Vercellino

12. FELIX JR.
Feb 14, 2016

THIS IS GOOD EXCEL PROGRAM IN THE CALCULATION OF % VOLTAGE STARTING DIP WHEN A LARGE MOTOR IS TARTED SUDDENLY EVEN WHEN ALREADY THERE’S EXISTING LOADS RUNNING.

13. Boomi
May 13, 2015

Very much informative and I like all spreadsheets
Regards,
Boomi

14. 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!

15. Abdulwahid
Jan 15, 2015