Re: Toroid = shorted turn ?

To: tesla-at-pupman-dot-com
Subject: Re: Toroid = shorted turn ?
From: "R M Craven" <craven-at-globalnet.co.uk> (by way of Terry Fritz <terryf-at-verinet-dot-com>)
Date: Fri, 09 Oct 1998 19:03:17 -0600
Approved: terryf-at-verinet-dot-com

<SNIP>

>>found we didn't need it for corona suppression after all.  I've never
>>noticed a top
>>toroid having a heat problem, but our top loads have always had a center
>disk.
>
>Right. It *looks* like a turn, but if there's a conductive center disk,
>it's *electrically* just a lump of metal as far as the coil's concerned.
>(Electostatic field-shaping effects notwithstanding :)


Nevertheless, eddy current heating will still occur for the reasons I
outlined originally, in the circumstances described,that Bert Pool was
responding to.

The problem is that the primary tank will induce currents directly in the
toroid. If you remove the secondary and run the primary alone but with the
topload stood on an insulating pillar, joule heating still occurs whether
the toroid is centre-disked or not. Unless your topload is zero resistance
at the frequency of interest.

Richard Craven, Malvern, England