Re: Some transformer theory

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Bunnykiller by way of Terry Fritz <teslalist-at-qwest-dot-net>" <bunikllr-at-bellsouth-dot-net>


>
>Next question:
>
>Can the root of the impedance ratio also be applied to flyback 
>transformers - are they "classical" transformers, or are they in the TC 
>bracket, where turns ratios cease to be entirely relevant?  I didn't have 
>one with a known turns ratio to test, but measured one and the ratio 
>*looked* sensible.
>
>Cheers
>
>M

Hi M ...

normally flyback transformers are made with a ferrite core...   they do 
behave differently. One of the "neet" things about a flyback ( or a ferrite 
cored Xfmr) is that they can be driven to a resonate state.  You can apply 
a voltage to them over a broad range and then all of a sudden you will see 
a tremendous peak in voltage on the secondary....

I found this out by experimenting with a smallish ferrite cored Xfmr from a 
photoflash ( a tad bit bigger than a sugar cube) ...   I was feeding the 
primary with a sine wave at about 2p-p volts while varying the frequency of 
the sine wave ...

from 50 Hz to 70KHz the output was on average 1:100...  at 80KHz I started 
to see a rise in the secondary....  at 100KHz  the 2 volts p-p sine 
wave  went to 600 volts secondary side  ( 1200 V p-p) ...   a 1:600 
ratio   now mind you...  the windings never changed :) obviously the 
frequency determines the output voltage :)

at 120 KHz the voltage dropped back down to the 1:100 ratio again...

so  in effect its safe to say that at 100KHz for this particulary Xfmr 
there is a resonate rise which produces its maximum voltage...

hmmm ...  I wonder of iron core Xfmrs have a simular reaction....


Scot D