Re: Toroid core losses

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Weazle,

On 5 Oct 2002, at 17:22, Tesla list wrote:

> Original poster: "J. B. Weazle McCreath by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <weazle-at-hurontel.on.ca>
> 
> 
> Hello Coilers,
> 
> I'm using a small RF choke as per instructions I got from Dr. Resonance
> to protect my PDT from stray RF finding it way into the windings, along
> with a horn gap type safety gap right at the PDT.
> 
> The choke consists of a toroid core I salvaged from a computer power
> supply with three turns of my high voltage lead from the PDT to the
> coil wound through it.
> 
> I noticed after about a minute run that the core was noticely warmer
> than it had been prior to firing.  Not hot by any means, but still a
> good deal above room temperature, telling me there is a bit of power
> being disappated.
> 
> What frequency do these computer power supplies do their switching at?
> Maybe the core material is not suitable at Tesla coil frequencies?
> My coil operates at 250 kHz, by the way. 

It isn't by any chance the load-balancing toroidal core (the one with 
a number of windings) is it? Those cores are iron powder and designed 
for high DC levels with a low level of ripple current. Subjecting 
them to high level flux swings is a guaranteed way to make them lose 
power.

Regards,
Malcolm