Re: Oscillator circuit for solid-state TC

To: tesla-at-pupman-dot-com
Subject: Re: Oscillator circuit for solid-state TC
From: RODERICK MAXWELL <major-at-vicksburg-dot-com>
Date: Fri, 18 Oct 1996 11:20:37 -0500
Tesla List wrote:
> 
> >From haba-at-cc.hut.fiThu Oct 17 22:19:40 1996
> Date: Thu, 17 Oct 1996 19:20:02 +0300 (EET DST)
> From: "Harri \"Haba\" Suomalainen" <haba-at-cc.hut.fi>
> To: tesla-at-pupman-dot-com
> Subject: Re: Oscillator circuit for solid-state TC
> 
> On Wed, 16 Oct 1996, Tesla List wrote:
> > I also worked out that most of the heat loss is in the primary,
> > rather than the secondary, Power loss will be current _squared_
> > times the resistance. the secondary may be longer n times the
> > number of turns but the current is only 1/n. You also have to figure
> > that the average diameter of the secondary windings is greater.
> 
> I had just the opposite. I wound a primary with lots of 0.25mm diam
> wires twisted. Secundary was on top of it. Secundary did have
> therefore longer average turn lenght as you suggest. Secundary
> was wound from 0.315mm diam wire which I had lying a round. Secundary did
> heat up signifficantly at 1kW+ power level. Nasty. I managed just to
> fit around 140 turns maxinum secundary on the core.. :( No room for
> bigger wire..
> 
> However, do read some transformer books. Minimize leakage inductance
> by interleaving primary and secundary. Minimize secundary capasitanse.
> If you do not take those precautions they may lead into lots of trouble.
> They did for me with traditional pwm-drives. With high turns ratio
> you may have secundary capasitance refled to primary side at tens
> of nanofarads easily!
> 
> > Spreadsheets are great for playing around with different values.
> 
> Indeed!
> 
> > The next design project will be a full bridge - advantages - efficency,
> > 375v working and single primary transformers. Disadvantage was
> > that I previously didn't know how to design it.
> 
> Good you do now. It definately has lots of advantages. Push pull were
> certainly great if 800V/10A fets at the speed of IRF740 were available
> at irf740 price. However, as they are not one will definately want
> to go for topologies minimizing the voltage stress.
> --
> Linux, free Unix for 386/486. Anonymous FTP: tsx-11.mit.edu or nic.funet.fi
> The only unix where even undocumented is documented! (try man undocumented)
> Harri.Suomalainen-at-hut.fi - PGP key available by fingering haba-at-alpha.hut.fi


  I hate to butt in but I wonder if you fellas could answer my question?
Can you wire more than one layer of secondary winding over the primary
without frying something?