Center tapped transformer equations

Discussion in 'Electronic Design' started by [email protected], Jan 30, 2006.

1. Guest

Hello. I have a frequency domain program that is using the following
equations for a transformer:
V1 = s(L1)(I1) +/- s(M)(I2)
V2 = s(L2)(I2) +/- s(M)(I1)

Where
+/- depends on the polarity
V1, V2 = voltages of primary and secondary
I1, I2 = currents of primary and secondary
L1, L2 = inductances of primary and secondary
M = mutual inductance

Does anyone know or can point me to a link that describes the frequency
domain equations for a center tapped transformer? Thanks.

2. Rene TschaggelarGuest

Just in case the transformer is with iron
core, forget the frequency domain.
Fourier transform assumes linearity,
which an iron transformer is not.

In case the transformer is air core, some
equations may be sufficient.

Rene

4. Ancient_HackerGuest

Those are very simplified transformer equations!

In the real world, transformers have distributed resistance and
capacitance and quite a bit of non-linearity at high fluxes, all of
which make simple models work not very well at high or low frequencies,
or high amplitudes.

Here's a web page with more advanced models you may find helpful:

http://tinyurl.com/7r5d7

5. Michael A. TerrellGuest

Why do you use that Tiny URL crap? Just post the real URL so someone
can still find the web page in a couple months:
<http://www.beigebag.com/case_xfrmer_2.htm> Quite often I will click on
one of those links to find that it has expired, or even worse it has
been reused.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

6. Ancient_HackerGuest

Because quite often the long url is full of funny characters that most
web browsers cant figure out are not delimiters.
Please show us ONE example of this.

As far as I know, and tinyurl claims, they never expire or reuse the
tiny URLS. For them to do so would be pointless, counterproductive,
and just plain dumb.

Maybe you're thinking of something else...

..

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

7. Michael A. TerrellGuest

More likely the browser software used to post the long URL is faulty
and breaks it into several parts. I simply add < and > around any
problem with the long link the redirect site still couldn't send you
there. Think about it. Also, you are posting through Goggle which is a
second or third rate method to access usenet.

I had archived several treads with those short URLs and they were all
bad or had been reused so i deleted them. Why would I keep them if they
didn't work?

No, it was one of these linking services that corrupted a lot of

On the other hand, why would you care if someone looks at the Google
archives in a couple years to find the link is bad? If they at least
knew the home page for the site they might luck out and find the
information anyway.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

8. Don ForemanGuest

Others have noted that transformers are nonlinear devices. Setting
that aside, perhaps your question is how to deal with a centertapped
xfmr or one with more than two windings.

For multiple windings you must set up the mesh equations with terms
for coupling from each winding to every other winding, as:

V1 = s(I1) L11 + s(I2)L12 + s(I3) L13 + ...
V2 = s(I1) L21 + s(I2) L22 + s(I3) L23 + ....
......
Vn = s(I1)Ln1 + s(I2)Ln2 + s(I3) Ln3 + ....+s(In) Lnn

This is further oversimple (beyond ignorinig nonlinearities) because
it ignores winding resistances.