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Oct 9, 2010 09:57 PM

Big news for fans of induction cooktops

I was just at my local electronics shop here in Japan and noticed that Panasonic is now selling "All Metal" induction cooktops. Not sure about the details because the catalog is in Japanese, but the guy at the store said that they work not only with stainless steel and cast iron cookware, but also with aluminum and copper. The price at the shop was about $2500-$3000 for a 3-zone cooktop (two of them 3.0-kW elements) with a built-in broiler drawer. That's a lot less than I paid for my "primitive" induction cooktop 5 years ago :(

Does anybody have any idea how these new cooktops work? I wonder whether the copper and aluminum compatibility is achieved by simply adding a conventional heating element under the glass surface. Can copper and aluminum be heated by induction?

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  1. Induction uses magnatism so, they must be dual element burners to heat aluminum. Did the unit on display work? Did it glow from a radiant element?

    8 Replies
    1. re: Sid Post

      Actually, you can induce a magnetic response from copper and aluminum at high frequency, like these:

      The science is not really new. The problem is that the energy transfer is low, so there is a lot of wasted energy for aluminum or copper cookware.

      1. re: Chemicalkinetics

        If you alter the frequency for copper and aluminum, won't that affect traditional iron?

        1. re: Sid Post

          Traditional cast iron cookware should work just fine with these higher frequency induction cooktop. I think they can operate in two frequencies.

          In the patent, it states: "In the second place, the fundamental resonant frequency (switching frequency) operated B-HB SLR HF inverter for IH is also demonstrated of magnetic and high resistivity metallic pans/utensils fabricated by iron, iron cast and stainless steel"

          So it seems it switches to a lower (still high) frequency for the traditional cast iron and 18/0 stainless steel cookware.

        2. re: Chemicalkinetics

          Oh, come on, Ck! How are you going to quantify "wasted energy" if the induction cook top wasting the energy only uses about 1/4 of the amount of energy a non-induction cook top uses? This is a HYPOTHETICAL EXAMPLE and I don't know if the equation is right so don't trounce me! My point is that you're making absolute statements about non-absolute things! '-)

          1. re: Caroline1


            First of all, induction cooking wastes energy by requiring electricity. Electricity energy itself requires conversion from other raw energy sources like coal and gas, so right there is the wasted energy. An induction cooktop does not heat up in your kitchen, but it heats up the power plants, whereas a gas stove does not heat up any power plant. The waste energy is pretty much the same for gas vs induction stovetops.

            Second, that whole thing about 90% electricity energy conversion between an induction stove and cookware is only true for a ferrours cookware. Let me give you a current example. If you are to put a copper cookware on your induction cooktop (and forces it stays on), you will have 0% efficiency (100% wasted energy). Your pan simply won't heat up, while the stove will heat up. By the way, not even all ferrous cookware get good induction heating efficiency. To put it simply, not all magnetic cookware are equally magnetic. The assumption that an induction stovetop always delivers ~90% efficiency between the stovetop and the cookware is simply not true.

              1. re: Chemicalkinetics

                "Electricity energy itself requires conversion from other raw energy sources like coal and gas"

                Not necessarily. My local electric utility offers the option to get your power from renewable sources for a fee. You can install solar panels on your roof. There are other ways of generating electricity than burning fossil fuels. But there's no renewable way to run a gas stove.

                "a gas stove does not heat up any power plant."

                I guess that's technically accurate, about as accurate as saying "a power plant does not spill oil into the Gulf of Mexico".

                1. re: Chemicalkinetics

                  Almost all electricity here in Qu├ębec comes from hydro. I don't think there is much else except some marginal experiments in wind and other environmentally-friendly energies.

          2. I'm curious how many hobs the model you saw had? I can only find Panasonic two and three burner cooktops on the web, and those with three only have two induction and one "regular" for non-induction pans. Panasonic has a LOT of great technology available OUTSIDE the United States! <sigh>

            EDIT Okay, I just re-read your post and it was three burner. Do you know if they offer a four induction burner unit? Thanks, and sorry for the sloppy reading on my part.

            1. I called up Panasonic Japan's customer service center today and talked to a lady about these new induction cooktops and also checked the Japanese website (which, unlike the printed catalog, I could run through some on-line translation tools).

              This is what I *think* I found out (within the limits of some rather garbled computer translations):

              Aluminum and copper pans are actually heated by induction, not by an additional conventional heating element. As pointed out by Chemicalkinetics, the induction elements operate at a higher frequency for these metals.

              For both aluminum and copper pans, the efficiency drops from the 90% or so for steel pans to around 75%. For this reason, the maximum power is limited to 2.5 kW instead of the rated 3.0 kW, the glass top tends to get hotter, and the cooling fans run louder. These limitations are all due to the higher frequency and greater electrical current needed to heat metals other than steel/iron.

              It appears that the cooktop automatically detects the material of the pan and switches the frequency accordingly.

              One really weird thing is that it seems aluminum pans experience a repulsive electromagnetic effect and tend to be "levitated" above the cooktop to some extent. Panasonic warns that aluminum pans should contain at least 700 grams of food to prevent them from sliding around or tipping over.

              To Caroline1: The catalog only shows two- and three-element models. Some of the three-element models are all induction (e.g., two 3-kW main elements and one 1.5-kW small element at rear center) and some replace the small element with a radiant element. If you want four elements, I wonder whether you could install two two-element units in a front/back configuration. The "All Metal" feature is currently available on only four models, and three of those have one "All Metal" induction element and one conventional induction element.

              Personally, my initial reaction was "I WANT!", but thinking it over a bit, I'm a little leery about buying one of these first-generation units. I generally prefer to wait until at least third-generation before jumping into new technology.

              OTOH, I am really excited about this development because it overcomes (to some degree, at least) one of the major limitations of induction cooking -- the need to use magnetic cookware.

              6 Replies
              1. re: tanuki soup

                eddy currents in aluminum is how cans are sorted by mechanical recycling separators. It's a big part of what makes single stream recycling practical. Run the waste stream through an overhead magnet, that picks out the ferrous stuff, then use a drop and eddy currents to separate the aluminum cans. The waste runs to the end of a conveyor belt, where it falls onto another belt, where it's sorted (manually) for glass, paper, plastic. Aluminum is repelled by an eddy current (usually generated by a spinning rotor, and not a solid state induction machine, but tyhe physics are the same), and instead of falling on the conveyor, it's thrown further by the eddy currents, and falls into a different container.

                  1. re: tanuki soup

                    "To Caroline1: The catalog only shows two- and three-element models. Some of the three-element models are all induction (e.g., two 3-kW main elements and one 1.5-kW small element at rear center) and some replace the small element with a radiant element. If you want four elements, I wonder whether you could install two two-element units in a front/back configuration. The "All Metal" feature is currently available on only four models, and three of those have one "All Metal" induction element and one conventional induction element.".....tanuki soup

                    Sometimes technology takes a giant step backwards instead of forward. When I bought this house five years ago, it was in serious need of some major tender loving care and upgrades, but hey, I got a great price on it. For the kitchen, I put in granite counter tops and wanted to put in induction at that time. There was a company that made single burner "built-in" induction hobs that looked like a lovely hand-painted ceramic tile. In fact, they WERE lovely hand painted ceramic tiles with an induction element sitting under them. I loved the idea of a black granite island with four or five ceramic tile insets with the controls hidden neatly from sight. To my great disappointment, the company stopped making them about ten months before I wanted to buy them.

                    At this juncture, I am pretty much restricted to an induction cook top that will fit into the cutout for my present radiant black glass cook top. I DO like the idea of being able to install all of the burners so that they are all "front burners." Great safety feature and you never have to reach across or around a boiling pot. But that would mean replacing the granite too.... <sigh> Where is that damn winning lottery ticket!!!!

                    1. re: Caroline1

                      "Where is that damn winning lottery ticket!!!!"

                      Do you buy lottery tickets to begin with?

                      1. re: Chemicalkinetics

                        WHAT??? Are you telling me I have to BUY lottery tickets to WIN??? |-( bummer....

                    2. re: tanuki soup

                      "New Technology" - if you've ever seen any of those "Home of the Future" newsreels from the 50s you may have come across a scene wherein a woman is cooking eggs in a pan that is floating above the cooktop. That's an aluminum pan, and the tech is not "new" as much as "re-discovered" to provide a market opportunity.

                    3. LOLOLOLOL!!! This thread's announcement is quite the capper to the chorus of "It can't be done!"s that appeared here DAYS ago. Caroline for President!

                      Of course your eggs will levitate, and your power provider will smile even more, and your copper will work like everything else. Say a prayer for the detection and fan circuitry. Maybe it'll even cut the birthrate!

                      1 Reply
                      1. re: kaleokahu

                        Of course it will cut the birth rate. Everybody will be in the kitchen watching their aluminum saucepans with only 300 grams of food in them dance around and play the Houdini game! OoOooOoooOOoooOOooooooo.... Halloween in the kitchen! '-)

                      2. Just wanted to bump this up and see if anyone has any more information on these "all metal" induction cooktops? Alibaba seems to have a ton of them floating around, but all made in China by Chinese companies, so not very confidence-inspiring.

                        12 Replies
                        1. re: Sirrith

                          Yup, 5 years on and All-Metal is nowhere in sight in USA. Or Europe AFAIK.

                          The manufacturers need to solve the detection, sensor and other electronic issues. Then they need to deal with the downtick in efficiency--if the idea is to sell induction as more efficient; that's probably why the Asian models employ dual frequencies.

                          IMO, the biggest issue--just like with the existing 24kHz "regular" frequency models--will be to pixelate or stitch together numerous coils for each hob, so as to produce uniform heat. I call this the torus problem.

                          All in a long-lived, dependable, affordable package?

                          My advice is not to wait up nights expecting all this anytime soon. Just buy gas if you have it available and you want to be able to use the best cookware.

                          1. re: kaleokahu

                            Call me a suspicious old broad, but I highly suspect that either there is an export ban on the broader wavelength induction cooktops and portable units OR there may be a health hazard involved that prevents Panasonic from marketing it in the U.S.

                            I can no longer access Japan, but I somehow managed a couple of years ago and TRIED to mail order one from the Japanese website for U.S. delivery. NO GO!!!

                            I might be wrong, but I do not believe any of the induction units that are effective on aluminum and copper are manufactured in China. I think they are exclusively Japanese manufacter, but that raises a serious paranoia question for me... WHY can't we buy the all metal induction cookers in the U.S.?????? I mean, Panasonic is not exactly a corporation that shies away from profit making endeavors. So why is this technology not in MY kitchen NOW??????????????

                            1. re: Caroline1

                              Possibilities abound.

                              One is as simple as an UL-197 listing.

                              Another may be getting the detection circuitry to recognize all pan types for what they are, distinguish the ferrous from non-ferrous, and enable use at the correct frequency, all without causing jewelry and utensils to burn the user.

                              Or it could be that the decision has been taken that they're not economically feasible or poor risks to manage in the US market.

                          2. re: Sirrith

                            If it's not Panasonic it's probably a mistranslation or referring to the exterior metal body of one product that then got lazily copy-pasted elsewhere. There's not much of a market for all-metal induction, though Panasonic is still trying to get customers for it as of 2014:

                            The problem is cost: why pay a premium for all-metal induction stoves up front? It's cheaper up front to get regular induction stoves and use regular induction-compatible stuff. You also pay an efficiency penalty and I think 75% is rather optimistic, particular for copper, but in any case you are paying more for electricity over time.

                            An energy-efficient (albeit expensive) solution to cooking on copper on induction would look like De Buyer's:

                            1. re: CenturyLife

                              Hi, Franz:

                              Have you compared the electricity used using conventional copper on a converter disk with compatible clad directly on the glass?


                              1. re: kaleokahu

                                Only with one combination so far and it was not good. But that was bumpy hammered copper. I will be doing some further comparisons with flat copper which is a fairer comparison (more surface area in contact with the disc).

                                1. re: CenturyLife

                                  Please do let us know how flat copper does with a converter disc. I'm very interested in this.

                              2. re: CenturyLife

                                <You also pay an efficiency penalty and I think 75% is rather optimistic>

                                75% is too optimistic for non-ferromagnetic. You probably get better efficiency by just using resistivity electric coil. Recent tests have even showed that the energy efficiency for induction is on par with electric coil, not better.

                                1. re: Chemicalkinetics

                                  I can believe that some shoddy induction stoves get below 80%, but it depends on the pan material/flatness and induction cooker components. Various tests I've seen have ranged from the low 80s to high 80s, Dept of Energy says 84% vs ~75% for electric coil.

                                  1. re: CenturyLife

                                    <Dept of Energy says 84% vs ~75% for electric coil.>

                                    I believe US Dept of Energy never did a test on induction cooktop until recently. The US DoE used to simply cite numbers from other places -- just as a reference, which is completely acceptable of course.

                                    1. re: Chemicalkinetics

                                      Yeah but electric utility and third party labs also cite 80-something percent and Panasonic itself cites 80-something for their cooktops, e.g., 86% for this one which is not all-metal:

                                2. re: CenturyLife

                                  Ahh, you might have hit the nail on the head. I didn't even think of the exterior body material as the "all metal" part.