Re: inductor/transformer concepts

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
> 
> Original poster: "Finn Hammer by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<f-h-at-c.dk>
 
> What you _do_ need to know, is how many turns/volt the coil needs to
> have, so that the core does not saturate, when it is unloaded.
> 
> Too __few_ turns, and the inductance gets too low-> the current gets too
> high, and the core saturates.
 
> Too many turns, and the wire will have to be too thinn, in order to cram
> it into the window,  and you get too much heat in the copper.
> 
> Luckily, you can determine the voltage per turn pretty easily: assemble
> the core around a winding of known turns, then apply voltage across the
> coil with a variac, measuring the current draw. Increasing the voltage,
> at a certain point, the current starts to increase rapidly.
> Back off the voltage a bit, and there you have your voltage across the
> coil. Divide with the amount of turns in the coil, and you get
> turns/volt.
> 
> This is all you need to know, in order to determine the turns needed to:
> 1 handle the voltage across the primary on the unloaded transformer
> 2 Calculate the turns needed on the secondary, to get the high voltage
> that you need.
> 
> Now set up a spreadsheet to calculate the space occupied in the window,
> with different wire thicknesses, and interleavings.
> 
> It is not that hard from a theoretical point of view, but it is labour
> intensive.
> 
> Cheers, Finn Hammer

	Everyone who asks about putting 220 volts on a 120 volt transformer to
boost the output should read this carefully.  The same principle applies
to primary circuit ballast inductors, of course, as well ferrite-cored
inductors, but saturation measurements of those are relatively hard to
conduct at high frequencies and simple calculation is easier.

Ed