
Homework Help Stuck on a textbook question or coursework? Cramming for a test and need help understanding something? Post your questions and attempts here and let others help. 

Thread Tools  Display Modes 
#1




Calculate number of turns in transformer
I need to find the required number of turns on the primary and the secondary windings of a transformer.
Given it is single phase 110/25KV railway TX on a 50Hz system the max flux density is 1.5Tesla when 1.13pu volts applied. assuming a core area of 0.3m2. How would I find this?? number of turns prim and sec 
#2




Quote:
I get the following Erms=222.14xNxAxBmax Did you mean the primary is 110kV? If it's 110kV (RMS) then for conditions at 1.13pu Vprim = 124.3kV So Np=123.4x10^3/(222.14x0.3x1.5)=1243 turns That's a big core CSA! [0.55mx0.55m] For the 25kV secondary Ns = 281 turns. These are very sparse specs for such a big unit. You haven't specified whether there a limitations on magnetizing current, losses, efficiency and a whole lot of other stuff. Do you intend to build this? 
#3




Make that Ns=283 turns

#4




Expert Answer
Hi Deano123,
Here is an answer from a top expert in the field, me! I have over 35+ years designing all kinds of transformers. I'm going to make it as simple as I can right now, as my time is very limited at the moment. This will require that you make a few conversions to use the CGS system, like 1.0 Tesla = 10,000 gauss. Here is the formula for the first winding, based on the known input voltage. Normally the primary, so I'll use that term: Np = number of primary turns. Vp = known primary input voltage in volts. I'm assuming a sine wave input. If it's a square wave input, remove the factor of 1.11 from the denominator. Bmax = maximum flux density in gauss. Ac = effective core area in cm^2 (convert from m^2). Fo = input frequency in Hz. Np= (Vp X 10^8) / (4)*(1.11)*Fo*Ac*Bmax In practice, you always roundup to the nearest integer turn. Then for the seconday turns, Ns = (Np*Vs)/Vp. This time, you can round up or down to the nearest integer turn, usually whichever is closest to the value you want. In practice, the effective core area not only depends on the actual core area, but the type of core, like EI laminations. Then it gets modified by the stacking factor; which depends on whether you interleave the laminations 1 by 1, 2 by 2, or buttjoin them. It also depends on the lamination or tapewound core tape thickness. The thinner the material, the closer to the actual measured core area. That's probably more than you wanted to know. If you have more questions, please ask. Good luck, Kamran Kazem 
#5




hi
what is the recommended frequency for 110v Ac and 220v ac 
#6




Whether you use my formula or kkazems you'll get exactly the same answer.
Something is seriously wrong with your specification if you really mean 110V primary. With a CSA of 0.3 m^2 at 50 Hz you'll need just 1.243 turns for the primary  even rounding up to 2 turns gives a ludicrous result. I think you need to recheck your spec. The CSA of 0.3m^2 is probably not what you intend. 
#7




others they specify the frequency, 60Hz for 120volts ac and 50Hz for 220volts ac...
what is the truth about this? 
#8




Quote:
There is a comprehensive listing here on wikipedia http://en.wikipedia.org/wiki/Mains_power_systems 
Tags 
calculate, number, transformer, turns 
Related Site Pages  
Section  Title  
Video Lecture  Transformers (Part 1)  Inductors,Capacitors,Transformers  
Video Lecture  Transformers (Part 2)  Analysis of Transformer Circuits  Inductors,Capacitors,Transformers  
Worksheet  Power conversion circuits  
Worksheet  Basic ACDC power supplies  
Worksheet  Advanced electromagnetism and electromagnetic induction  
Worksheet  Impedance matching with transformers  
Worksheet  Stepup, stepdown, and isolation transformers  
Worksheet  Mixedfrequency signals  
Worksheet  Seriesparallel combination AC circuits  
Textbook  Numbers and symbols : Numeration Systems 
Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Microwave transformer help?hope this is the right place  has91  General Electronics Chat  5  01132009 08:17 AM 
to calculate transformer windings  ronald.dias  Homework Help  2  08192008 02:08 PM 
Urgent answer needed about the number of windings of transformer  muhsiul hassan  Homework Help  6  08182008 10:49 AM 
relationship between core size and turns in transformer  adeel  General Electronics Chat  2  07192008 05:04 PM 
Transformer for Capacitor Discharge circuit  Xray  General Electronics Chat  4  05192008 01:18 PM 
Thread Tools  
Display Modes  

