I am trying to work out the BW of my transformer

  • Thread starter Thread starter KennyB
  • Start date Start date
  • Tags Tags
    Transformer Work
Click For Summary

Discussion Overview

The discussion revolves around calculating the bandwidth (BW) of a transformer, focusing on the lower and upper -3dB points based on given parameters such as source resistance, load resistance, winding ratio, and magnetizing current. Participants explore the implications of these calculations in the context of high-frequency behavior and practical measurement challenges.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant outlines the process for determining the lower -3dB point, expressing confusion about the interaction between leakage inductances and magnetizing current.
  • The same participant questions the application of Thevenin's theorem in calculating the upper -3dB point, noting the relationship between primary and secondary winding leakage inductances.
  • Another participant raises concerns about stray capacitance at high frequencies, suggesting that resonances may complicate the attenuation/frequency curve and that real-world measurements are necessary for accurate results.
  • New participants express a desire to learn more about transformer calculations, indicating a need for foundational knowledge and specific guidance.

Areas of Agreement / Disagreement

There is no consensus on the calculations or the implications of high-frequency behavior. Multiple viewpoints exist regarding the theoretical versus practical aspects of transformer analysis.

Contextual Notes

Participants highlight limitations related to high-frequency behavior, including the impact of stray capacitance and the challenges of real-world measurements versus theoretical calculations.

Who May Find This Useful

This discussion may be useful for individuals interested in transformer design, high-frequency circuit analysis, and those seeking foundational knowledge in electrical engineering concepts related to transformers.

KennyB
Messages
1
Reaction score
0
I am trying to work out the BW of my transformer.


My source resistance, Rs, is 50R. My load resistance, RL=50R. The windings ratio ,N, is 1:1. The magnetising current, Lmag=7.96uH. The data i have suggests that to find the lower -3dB point, you refer the secondary load to the primary. This gives RL'=50R. In order to find the cut off point, the resistance of the primary is equated to the reactance of Lmag. The combined resistance is defined as Rs//RL'= 50R//50R = 25R. The lower cut-off is then evaluated as 500KHz. A little confused by this because although the leakage inductances are essentially shorts at this frequency, Lmag appears in // with the primary referred load, RL'...and these two components combined are in // with Rs. Unsure.

Now for the upper -3dBpoint...the data now says that the total resistance is Rs + RL'. Why is Thevenin's not applicable here?! The primary winding leakage inductance equals the secondary winding leakage inductance = (1-K)*Lmag where K = 0.998333. The upper -3dB point was evaluated as 600MHz.

Can somebody please clear this up for me?

PS: The reason why I'm interested in the maths of this is that i want to input this data into SIMetrix for analysis with additional analogue front-end circuitry.
 
Last edited:
Engineering news on Phys.org


There will be stray capacitance involved at 600MHz which may produces resonances. I wouldn't expect the attenuation/frequency curve to be smooth. There might be frequencies where the attenuation becames very high..deep nulls. Any core material will behave differently at UHF compared to LF. There will be so many unknowns that it will be impossible to calculate. The only way is measurement of a real transformer. Even then terminations and even short lengths of coax will distort the results.

If you consider it as a purely (ideal) mathematical exercise that is a different thing.
 


helo pro Engs.

I am new here i will like to know more of this transformer calculation .i intend to be faithful explain to ,i am expecting thing of fabulous ...


Thanks
rasheed
 


chedor said:
helo pro Engs.

I am new here i will like to know more of this transformer calculation .i intend to be faithful explain to ,i am expecting thing of fabulous ...


Thanks
rasheed

Welcome to the PF, chedor. What is your background so far with transformers? Have you read the introduction to transformers at wikipedia.org yet? If you have specific questions, you could start a new thread here (or in the Homework Help forums if your questions are for schoolwork), and list your specific questions.
 


thanks for early reply...i am new in the field but i have faith that with time i will be a profeesional ,the you have email.. that we can dicus better that this..i have little idea of transformer ..

thanks
rasheed
 

Similar threads

Maximum power from a transformer
  • · Replies 8 ·
Replies
8
Views
3K
How does back EMF contribute to the operation of an autotransformer?
  • · Replies 64 ·
3
Replies
64
Views
8K
Power Transmission Line and Transformer Parameters
  • · Replies 2 ·
Replies
2
Views
2K
Engineering How do short/open-circuit tests work for step-up transformers?
  • · Replies 7 ·
Replies
7
Views
3K
The lesson of electric machines and drivers - transformer questions
  • · Replies 4 ·
Replies
4
Views
2K
Determining voltage in transformers
  • · Replies 11 ·
Replies
11
Views
3K
Engineering Why Conduct Open-Circuit and Short-Circuit Tests on a Transformer?
  • · Replies 2 ·
Replies
2
Views
7K