Re: CCFL transformer

On 26/04/2024 12:52 am, legg wrote:

On Wed, 24 Apr 2024 01:57:36 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
>

Hi
>
I need a low distributed capacitance winding transformer, for a HV
stepup function (3.5kV)
>
I am zeroing in on similar concept as CCFL transformers with
sectionalized bobbin.
>
For example:
>
https://www.coilcraft.com/en-us/products/transformers/power-transformers/ccfl-transformers/fl/
>
Possibly using Triple Insulated Wire to create some distance between the
individual turns.
>
Not many sells CCFLs these days.
>
Guess I will keep it alive....
>
Regards
>
Klaus

>
Stress between turns is limited by v/n limit of core. It's layer
stress and section stress that you have to deal with.
That's what the multisection bobbin and pancake windings do.

 They also reduce the parallel capacitance of the windings, and give you are higher resonant frequency for the transformer as a whole.
 "Layer stress" and "section stress" aren't specific electronic engineering terms, and the "v/n" limit of the core is pretty vague.
 There is a volt per turn limit imposed by the magnetic field that saturates the core - but at higher frequencies you can tolerate more volts per turn before the core saturates - it's a linear function of switching frequency, up to the point where resistance around the current loops inside the core lets enough current circulate to heat the core above its Curie temperature.
 

If the CCFL transformer will allow only 1600V, imagine the
precautions required for 3x that stress. I'm not sure you
can avoid vacuum impregnation / potting in anything 'small'.

 Imagination does seem to be what's being applied here.
 There's a least one truly horrible 1969 text book on transformer design
 https://www.amazon.com.au/Soft-Ferrites-Applications-C-Snelling/dp/0408027606
 and it took me years to realise quite how confusing it was.