Kompor Induksi [2]

How does an induction cooker do that?

Put simply, an induction-cooker element (what on a gas stove would be called a "burner") is a powerful, high-frequency electromagnet, with the electromagnetism generated by sophisticated electronics in the "element"

under the unit's ceramic surface. When a good-sized piece of magnetic material--such as, for example, a cast-iron skillet--is placed in the magnetic field that the element is generating, the field transfers ("induces") energy into that metal. That transferred energy causes the metal--the cooking vessel--to become hot. By controlling the strength of the electromagnetic field, we can control the amount of heat being generated in the cooking vessel--and we can change that amount instantaneously.

(To be technical, the field generates a loop current--a flow of electricity--within the metal of which the pot or pan is made, and that current flow through the resistance of the metal generates heat, just as current flowing through the resistance element of a conventional electric range's coil generates heat; the difference is that here, the heat is generated directly in the pot or pan itself, not in any part of the cooker.)

How Induction Cooking Works:

1. The element's electronics power a coil (the red lines) that produces a high-frequency electromagnetic field (represented by the orange lines).
2. That field penetrates the metal of the ferrous (magnetic-material) cooking vessel and sets up a circulating electric current, which generates heat. (But see the note below.)
3. The heat generated in the cooking vessel is transferred to the vessel's contents.
4. Nothing outside the vessel is affected by the field--as soon as the vessel is removed from the element, or the element turned off, heat generation stops.

(Image courtesy of Induction Cooking World)

(Note: the process described at #2 above is called an "eddy current"; heat is also generated by another process called "hysteresis", which is the resistance of the ferrous material to rapid changes in magnetization. The relative contributions of the two effects is highly technical, with some sources emphasizing one and some the other--but the general idea is unaffected: the heat is generated in the cookware.)

(You can see what such a coil and its associated electronics looks like in the image at the right.)

There is thus one point about induction: with current technology, induction cookers require that all your countertop cooking vessels be of a "ferrous" metal (one, such as iron, that will readily sustain a magnetic field). Materials like aluminum, copper, and pyrex are not usable on an induction cooker. But all that means is that you need iron or steel pots and pans. And that is no drawback in absolute terms, for it includes the best kinds of cookware in the world--every top line is full of cookware of all sizes and shapes suitable for use on induction cookers (and virtually all of the lines will boast of it, because induction is so popular with discerning cooks). Nor do you have to go to top-of-the-line names like All-Clad or Le Creuset, for many very reasonably priced cookware lines are also perfectly suited for induction cooking. But if you are considering induction and have a lot invested, literally or emotionally, in non-ferrous cookware, you do need to know the facts. (Check out our page on Induction Cookware.)

(And there are now available so-called "inductions disks" that will allow non-ferrous cookware to be used on an induction element; using such a disk loses many of the advantages of induction--from high efficiency to no waste heat--but those who want or need, say, a glass/pyrex or ceramic pot for some special use, it is possible to use it on an induction cooktop with such a disk.)

On the horizon is newer technology that will apparently work with any metal cooking vessel, including copper and aluminum, but that technology--though already being used in a few units of Japanese manufacture--is probably quite a few years away from maturity and from inclusion in most induction cookers. If you are interested in a new cooktop, it is, in our judgement, not worth waiting for that technology.

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