Residental electrical load [was Re: Who's rewired their house for this hobby?]
cclist at sydex.com
Fri Nov 28 00:53:00 CST 2014
On 11/27/2014 09:51 PM, drlegendre . wrote:
> In the case of most copper, antimagnetic stainless or aluminum vessels, the
> eddy currents actually propagate a bit too well - that is, the effective
> resistance of the imposed current path is too low for any useful ohmic
> heating to take place. In other words, the currents flow, but the voltage
> drops are inconsequential.
Well, my view is that the substance being heated has to have a
sufficiently high relative permeability to work--and in a way, it's tied
into your resistive explanation. There isn't a lot of electrical
difference with 18 percent chromium stainless steels, but the 10 percent
nickel is a game killer in 18/10 stainless.
I've got a sheet of pure nickel, which is ferromagnetic. I should give
it a try on my cooker and report back.
A high-permeability ferromagnetic substance will tend to support
formation of a magnetic field at fairly shallow depths in the material,
and thus induction of a current and subsequent heating.
Were this a purely resistive effect, a sheet of very thin copper foil or
a graphite disk would also be great candidates for induction heating,
which (I can verify this by experimentation) they aren't. isn't. Of
course, the frequency has an effect as well.
I think of it as a transformer with a shorted winding. At induction
cooker frequencies, the coupling will be stronger if a ferromagnetic
core is used.
Maybe we're arguing two sides of the same coin?
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