Re: CCFL transformer

On Thu, 25 Apr 2024 22:28:54 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:

On 25-04-2024 16:52, 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.
 

>
Yes, but there will loss associated with the distributed capacitance
between turns, that's why I am trying to reduce that one also
>

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'.
 

>
I am actually working on an alternative idea, using 2 CCFL transformers,
since as you write they are normally rated for 1600V. Incidentially, the
1600V is the start voltage, runs steady state at 600V.
>
The idea is to parallel 2 CCFL transformers primary winding, and series
connect the secondary windings. Then connect the center tap to GND, that
way I get -1600V and +1600V, total 3200V without violating the ratings
of the transformer

1600V is a proof test voltage for the part - not a continuos rating.

If your application is a CCFL one, then go for it. That's COTS.

If it requires a continuos high voltage, you will need to take
extra precautions.

RL