Why do induction cooktops require ferromagnetic cookware?
Why do induction cooktops require ferromagnetic cookware?
(OP)
I am playing around with induction heating at present.
I have a couple of Chinese-built royer oscillator drivers, one good for ~100W and its big brother (~1000W). Both of these will easily heat steel, stainless steel, copper, aluminium, lead, the 1000W driver even comes with a carbon crucible which also heats nicely when put inside the coil.
No real surprises here, it works after all just a transformer, the heating target just needs to be conductive in the same way that a transformer winding is good in copper or aluminium.
So why, then do cookpots for induction cooktops need to be ferromagnetic?
My working explanation is that the cooktops are optimised for ferromagnetic pots, and while they would heat a copper or aluminium, they cannot do so efficiently, and may overheat as a result.
Can anyone confirm or improve on my working explanation?
I have a couple of Chinese-built royer oscillator drivers, one good for ~100W and its big brother (~1000W). Both of these will easily heat steel, stainless steel, copper, aluminium, lead, the 1000W driver even comes with a carbon crucible which also heats nicely when put inside the coil.
No real surprises here, it works after all just a transformer, the heating target just needs to be conductive in the same way that a transformer winding is good in copper or aluminium.
So why, then do cookpots for induction cooktops need to be ferromagnetic?
My working explanation is that the cooktops are optimised for ferromagnetic pots, and while they would heat a copper or aluminium, they cannot do so efficiently, and may overheat as a result.
Can anyone confirm or improve on my working explanation?





RE: Why do induction cooktops require ferromagnetic cookware?
It's called an "induction cooktop" not because it's an induction heating system, but because calling it anything else with the term "flux" in it would cause too many snickers in the retail consumer world!
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
RE: Why do induction cooktops require ferromagnetic cookware?
https://en.wikipedia.org/wiki/Permeability_(electr...)
See also;
https://en.wikipedia.org/wiki/Induction_cooking
"I have not failed. I've just found 10,000 ways that won't work." Thomas Alva Edison (1847-1931)
RE: Why do induction cooktops require ferromagnetic cookware?
Now, in an induction cooktop, the same principle is being applied, but we have to have a workpiece (the pot) made from iron, steel or stainless steel.
Could it be that this is because the ferromagnetic material couples to the induction coil more effectively, leading to a more efficient power transfer?
RE: Why do induction cooktops require ferromagnetic cookware?
Inductive heating of brass requires a much larger RF generator than iron or steel, and you can get a decent induction cooktop that about the size of a old school laptop.
TTFN (ta ta for now)
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RE: Why do induction cooktops require ferromagnetic cookware?
The wikipedia articles referenced be GroovyGuy above, and the article on induction heating are most helpful.
Induction cooktops require ferromagnetic cookpots because they rely on a combination of eddy-current and magnetic hysteresis to generate the heat. They operate at around 24KHz.
My toy induction heaters, when heating non-ferromagnetic metals, generate the heat purely through eddy current heating. The oscillators runs at an as-yet-unmeasured much higher frequency than the cooktop. I'd expect, if a small steel item is heated through the curie point, to see a change in frequency and power as the mode changes.
RE: Why do induction cooktops require ferromagnetic cookware?
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm