Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: legg Newsgroups: sci.electronics.design Subject: Re: CCFL transformer Date: Fri, 26 Apr 2024 10:57:24 -0400 Organization: A noiseless patient Spider Lines: 62 Message-ID: <06gn2jh80t3l7i2sk4uvu1srujqare99r2@4ax.com> References: <66rk2jl35lbgd2tnqc6jjoqsd70ig9d485@4ax.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Injection-Date: Fri, 26 Apr 2024 16:55:48 +0200 (CEST) Injection-Info: dont-email.me; posting-host="ffb4f4ce7bbbd7c9ba305c473bbfabda"; logging-data="3950572"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+lL56NGFfeRS+AZ4an1doZ" Cancel-Lock: sha1:v5jpBJuidylR1zDGn8ZdHm/1K4w= X-Newsreader: Forte Agent 4.2/32.1118 Bytes: 3216 On Fri, 26 Apr 2024 01:36:06 +1000, Bill Sloman wrote: >On 26/04/2024 12:52 am, legg wrote: >> On Wed, 24 Apr 2024 01:57:36 +0200, Klaus Vestergaard Kragelund >> 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. https://archive.org/details/SNELLING__SOFT-FERRITES__1969/page/n13/mode/2up?view=theater RL