Residental electrical load [was Re: Who's rewired their house for this hobby?]

[Chuck Guzis]

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?

--Chuck