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From: legg <legg@nospam.magma.ca>
Newsgroups: sci.electronics.design
Subject: Re: CCFL transformer
Date: Fri, 26 Apr 2024 10:33:26 -0400
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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