Power And Distribution Transformers Sizing Calculations – Part Eight



Subject Of Previous Articles
Article
Glossary of Sizing Power and Distribution Transformers,
 
 
Resources used to calculate basic ratings of power and distribution transformers
 
the selection factors for the Power and Distribution Transformers
 
Applicable calculations procedures for sizing of power and distribution transformers
 
1-Applicable procedures for calculating power and distribution transformer ratios,
2-Applicable procedures for calculating power transformer efficiency,
3-Applicable procedures for calculating power transformer voltage regulation,
4-Special Cases In Transformers Sizing Calculations: Secondary Unit Substations
 
 
 
Special Cases In Transformers Sizing Calculations: Paralleled Transformers
 
 
Special Cases In Transformers Sizing Calculations: K-Factor Transformers
 
Note: I’d like from all of you to review our course “EP-3: Electrical Procurement – Transformers Courseto be more familiar with the contents of our new articles about the Power and Distribution Transformers sizing calculations.
 
Today, we will explain other special cases for Power and Distribution Transformers sizing calculations; K-Factor/Factor K Calculator and Spreadsheet.
 

 
 

 
Special Cases In Transformers Sizing Calculations

 

K-Factor/Factor K Calculators
 

 

 
Here we will study the programs and excel spreadsheets used for calculation of K-Factor/Factor K used in sizing transformers with non-linear loads, these programs and excel spreadsheets are:
 
  1. K-Factor/Factor K Calculator,
  2. Transformer Calculations Spreadsheet.
 

 

 
1- K-Factor / Factor K Calculator
Note:
This program is designed to assist in the calculation of K Factors. It should be used for reference purposes only and users should verify that the results are valid for their particular circumstances.

 

 
Introduction
This software calculates the K-Factor of a load from the harmonic content according to US and European practice. The results can be used to select transformers or to determine suitable de-rating factors for transformers.

 

 
How to use?
 
We will explain the following points to show how this program can be used in the calculation of  K-Factor / Factor K:
 
  • First: Installation,
  • Second: Running The Program,
  • Third:  The Main Window,
  • Forth: Making New Calculation File,
  • Fifth: Examples for K-Factor,
  • Sixth: Examples for Factor K.
 

 

 
First: Installation
  1. Double click the K-Factor-Calculation.exe file to install it.
  2. The program will be installed to the following directory:
            C:\Program Files (x86)\Copper Development Association\K-Factor Calculator\
 



 

 

 
Second: Running The Program
  • From the start menu, click on the file KFC.exe to open it,
  • Once the program opens, you will find the option to select the user’s language from English and Francais,
 
  • Also, you will find option to select between:
 
 
  • Open existing file: thus will take you to a new window of the K-Factor directory where you can change an existing calculation file or save a new calculation file.
 
  • New file: this will open a new calculation file. In the new calculation file you can select between calculating K-Factor according to the US standards or Factor K according to the European standards.
  • Exit: this will end the program.
 

 

 
Third:  The Main Window
The main window of the program have two drop down menus as follows:
A- File drop down menu:
 
 
Where you can select again between the following options:
  1. Open
  2. New
  3. Exit
  4. Save: A new option is “Save” where you can save your new calculation file or your modification to an existing calculation file.
B- Method drop down menu:
 
 
Again you can select, from this drop menu, between calculating K-Factor according to the US standards or Factor K according to the European standards.
 

 

 
Forth: Making New Calculation File
A- Input data:
When selecting calculating K-Factor according to the US standards, the Magnitude of each harmonic order, shall be entered and this can be done by two different methods:
  • Method#1: Holding down shift, click and drag in a harmonic order to set the magnitude.
 
  • Method#2: Alternatively, right click in a harmonic order and type the magnitude in the edit box. Click enter to accept.
 
  • To delete a line/ harmonic order magnitude: Hold down control and click.
 
As a summary to entry data steps:
  • Add/adjust: shift-click
  • Set value: Right click
  • Delete: Ctrl- click
 
B- Output Data:
In case of K-Factor calculations: the output data will be as follows:
  1. RMS Current,
  2. K-Rating.
 
 
In case of Factor K calculations: the output data will be as follows:
  1. Fundamental Eddy Current Loss,
  2. Eddy current loss exponent,
  3. RMS Current,
  4. Factor K de-rate to.
 
 

 

 
Fifth: Examples for K-Factor
here are some examples for using this calculator to find K-Factor:
 
 
 
 
 
 

  

 
Sixth: Examples for Factor K
 
here are some examples for using this calculator to find Factor K:
 
 
 


 
 
 

 

 
2- Transformer Calculations Spreadsheet
 
 
 
The Transformer Calculations Spreadsheet consists of two parts:
 
  • First part: Transformer Rating Calculator,
  • Second part: Transformer Harmonic Calculator.
 

  

 
First part: Transformer Rating Calculator
 
 
Enter values in yellow cells only. Other cells will be calculated.
Input data:
  • Full-load rating in KVA
  • Line-To-Line primary voltage in volt
  • Line-To-Line secondary voltage in volt
  • And SNL Standard Impedance in % will be selected from Impedance Lookup Table.
 
 
 
Output data:
  • Primary current, FLA in amps
  • Secondary current, FLA in amps
  • Primary fuse, max of 300% in amps
  • Primary fuse, min of 125% in amps
  • Secondary breaker, 125% in amps
  • Fault duty, primary in amps
  • Fault duty, secondary in amps
 

 

 
Second part: Transformer Harmonic Calculator
 
 
 
Enter values in yellow cells only. Other cells will be calculated.
Input data:
 
  • Fundamental current in amps
  • Third Harmonic current in amps
  • Fifth Harmonic current in amps
  • Seventh Harmonic current in amps
  • Ninth Harmonic current in amps
  • Eleventh Harmonic current in amps
  • Thirteenth Harmonic current in amps
  • Fifteenth Harmonic current in amps
 
 
Output data:
  • Calculated RMS current, FLA in amps
  • Calculated Harmonic Factors - K-Factor
  • Calculated Harmonic Factors - FHL-Factor
 
Notes:
 
  • K-Factor is calculated on RLA, FHL-Factor on rated FLA
  • Use 100 amps for per-unit, otherwise use measured loads
  • For Fifth Harmonic current, Use 1/7th of RLA for VSD drives
  • For Seventh Harmonic current, Use 1/7th of RLA for VSD drives
 

  

 
To download your copy of K-Factor/Factor K Calculator, click on the link.
 
To download your copy of Transformer Calculations Spreadsheet, click on the link.
 
Note:
 
Non-registered members in Electrical-Knowhow website will not be able to open and use the program and excel spreadsheet.
 
To register as a member of Electrical-Knowhow website, do the following:
  1. Click on “Follow" in bottom of the home page, below the images of our members.
  2. After finishing your registration send email to ali1973hassan@yahoo.com, asking for your password and I will send it with email reply.

 
 

 
In the next article, we will continue discussing the last special case for Power and Distribution Transformers sizing calculations which will be Transformers with Large Motor Loads. So, please keep following.

 


 

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