I am trying to work out the BW of my transformer

  • Thread starter Thread starter KennyB
  • Start date Start date
  • Tags Tags
    Transformer Work
AI Thread Summary
The discussion focuses on calculating the bandwidth (BW) of a transformer with specific parameters, including source and load resistances, winding ratio, and magnetizing current. The lower -3dB point is determined to be 500KHz, while the upper -3dB point is evaluated at 600MHz, raising questions about the application of Thevenin's theorem in these calculations. The user expresses concerns about the impact of stray capacitance at higher frequencies, which could lead to resonance and non-smooth attenuation curves. Additionally, the complexity of real-world measurements is highlighted, noting that ideal calculations may not reflect actual performance due to various unknowns. Overall, the user seeks clarity on these calculations and their implications for transformer analysis in simulation software.
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
 

Thread 'Underwater piezoelectric sensor array receive sensitivity'

Hi all I have some confusion about piezoelectrical sensors combination. If i have three acoustic piezoelectrical sensors (with same receive sensitivity in dB ref V/1uPa) placed at specific distance, these sensors receive acoustic signal from a sound source placed at far field distance (Plane Wave) and from broadside. I receive output of these sensors through individual preamplifiers, add them through hardware like summer circuit adder or in software after digitization and in this way got an...
View full post »

Thread 'Question about bonding ground and neutral'

I am not an electrical engineering student, but a lowly apprentice electrician. I learn both on the job and also take classes for my apprenticeship. I recently wired my first transformer and I understand that the neutral and ground are bonded together in the transformer or in the service. What I don't understand is, if the neutral is a current carrying conductor, which is then bonded to the ground conductor, why does current only flow back to its source and not on the ground path...
View full post »

Thread 'Following up on the recent thread about Earth Resistance measurements'

I have recently moved into a new (rather ancient) house and had a few trips of my Residual Current breaker. I dug out my old Socket tester which tell me the three pins are correct. But then the Red warning light tells me my socket(s) fail the loop test. I never had this before but my last house had an overhead supply with no Earth from the company. The tester said "get this checked" and the man said the (high but not ridiculous) earth resistance was acceptable. I stuck a new copper earth...
View full post »

Similar threads

Maximum power from a transformer
Replies
8
Views
3K
How does back EMF contribute to the operation of an autotransformer?
2
Replies
64
Views
7K
Power Transmission Line and Transformer Parameters
Replies
2
Views
2K
Engineering How do short/open-circuit tests work for step-up transformers?
Replies
7
Views
3K
The lesson of electric machines and drivers - transformer questions
Replies
4
Views
2K
Determining voltage in transformers
Replies
11
Views
3K
Engineering Why Conduct Open-Circuit and Short-Circuit Tests on a Transformer?
Replies
2
Views
7K
I Progress In Calculating The HLbL Contribution To Muon g-2
Replies
0
Views
2K

Hot Threads

Recent Insights

Back
Top