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From: legg <legg@nospam.magma.ca>
Newsgroups: sci.electronics.design
Subject: Re: CCFL transformer
Date: Fri, 26 Apr 2024 10:43:48 -0400
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On Thu, 25 Apr 2024 21:10:14 -0000 (UTC), Jasen Betts
<usenet@revmaps.no-ip.org> wrote:

>On 2024-04-25, legg <legg@nospam.magma.ca> 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.
>>
>> 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 see trandformers claimed for 15kV with 6 sections of loose wound
>magnet wire.  This is however Chinese consumer marketing kilovolts.
>
>https://www.aliexpress.com/item/1005002225061453.html
>
>Given the ~2mm spark gap it suggests something less than 15kV

For the price, these would all be fair exercises in 'why you can't 
do that'. 

Applications requiring temporary high voltages, particularly those 
feeding 'spark gaps', are basically protected by the load.

Physical separation of primary and secondary, reinforced by layered 
core insulation (automatic doubling) and filled gaps are basic 
techniques of achieving higher proof withstand voltage stress 
capabilities.

I'm past slagging Chinese product. They deliver - We don't.

RL

RL