Talk:Induction cooking/Archive 1

Image
Note that the image shown does not feature an induction cooker. It shows a class-ceramic cooktop allright, but the burners are electric resistor coils. Lupo 10:02, 12 November 2005 (UTC)

Are all four? I think the dual-ring ones might be IH, but if they're all resistor coils, then we can remove the link. Neier 10:46, 12 November 2005 (UTC)


 * All four. The dual-ring ones have two heating zones: either you switch on just the center, or you additionally switch on the ring. Lupo 07:56, 14 November 2005 (UTC)

Sears has a relatively inexpensive induction cooktop. It has four burners. I have a single burner (available for around 100 dollars). It is super efficient and I think it's better than gas. A cup of water boils in seconds see this web site for image and further information http://www.sears.com/sr/javasr/product.do?BV_SessionID=@@@@1036968486.1140492640@@@@&BV_EngineID=cciiaddhdfhdhmicegecegjdghldfoo.0&vertical=SEARS&sid=I0093600010003900085&pid=02242800000

Also, the image showing an induction coil showing through a fan opening is misleading. True it is an induction coil, but it's a part of the electronic circuitry (probably a mains filter) and not the induction coil used for heating. I'll take some photos next time I open my (broken) hob up for another go at fixing it! Tsh 18:12, 1 March 2007 (UTC)

Cookware
I believe that the needs for special 'Induction Cookware' are not sufficiently covered. Induction Cookware might even need a Wikientry of its own. One practical tip a potential buyer of an Induction hob will face is - how much will he/she need to invest in new cookware? If there is a simple way to test a piece of cookware for being useful for induction cooking, please share. E.g. - if a magnet sticks to a pan/pot - is that enough? Can a pan/pot work with induction if a magnet does not stick to it? If a wrong cookware is used - will it just not cook - or will there be damage? —Preceding unsigned comment added by 195.207.101.112 (talk) 14:07, 27 December 2007 (UTC)

Radiation
Does anybody have any data on the radiation emitted by these things? A quick google search yielded at least one safety warning for one brand. Rōnin 18:40, 5 December 2005 (UTC)


 * Try "The Induction Site" - Induction Cooking - Radiation Hazards? Owlcroft 10:13, 8 December 2005 (UTC)

Merge with Induction Range
I suggest any content covered by Induction range and not covered in the (larger) Induction cooker article is incorporated in Induction cooker, and the Induction Range article made into a redirect to Induction cooker, with a note in the article to the effect that induction cookers are known as induction ranges in the USA. WLD 16:16, 18 July 2006 (UTC)

"I think the person was talking about using an induction coil in space or on the surface of the moon." Comments about content should be in the discussion page, however, this disagreement needs to be resolved.

Heating
An induction cooker actually generates most of it's heat due to hysterisis losses in the ferromagnetic material, not because of the eddy current's generated within the material. The eddy currents only contribute to a fraction of the heating. So the 3'rd paragraph of the article here mis-directs people by saying: "Since heat is being generated from an electric current induced by an electro-magnet...". Any thogughts on this? --Pavithran 08:07, 31 October 2006 (UTC)
 * Agree. How would you recast that paragraph? WLD 09:17, 31 October 2006 (UTC)
 * I'm a little confused about this section too. It would be nice if an expert could rewrite the section, or shed some light on the topic? I'm also inclined to believe hysteresis is the main heat source since the bottom of pans and pots made for induction cookers have magnetic cores, but I'm just guessing? Apis O-tang 17:30, 6 September 2007 (UTC)

Does anyone have any source for the information in this line: "After boiling a pot of water, the surface of an induction stove is slightly warm to touch but not so warm as to burn or even hurt human flesh. Furthermore, within 1 to 5 seconds it cools to room temperature."? Aron G, Eh? 01:54, 1 December 2006 (UTC)

here is a funny one: "cookware must be magnetically conductive." I just thought I would throw that one in to emphasize the level of failure in this article. —Preceding unsigned comment added by 70.177.16.146 (talk) 03:27, 12 September 2008 (UTC)

Skin depth
This article gives the skin depth for Aluminum as 12mm (without stating the frequency). The Skin depth article, however, shows how to calculate the skin depth at the relevant frequencies, and those formulas give a value of 0.6mm for 20kHz. If that is true, why can't you use aluminium or copper (which has a similar skin depth) with induction? (Both materials work well with magnetic braking.) —Preceding unsigned comment added by Popup (talk • contribs) 10:20, 3 October 2007 (UTC)

Because it is not eddy currents as with magnetic braking that does the heating, but ferromagnetic hysteresis. An outer layer greatly exceeding the skin depth would prevent the magnetic field from entering the cooking vessel. The limitation would be that the ferromagnetic layer should not be covered by a too thick non-ferromagnetic conductive layer. —Preceding unsigned comment added by 84.132.82.198 (talk) 04:31, 5 November 2007 (UTC)

Term: "Hob"
This term is used repeatedly through the article unreferenced. In context it appears to mean "cooktop" or "hot plate", but there is only one limited explanation for the term. There is a reference in the dictionary to hob as a noun meaning "a projection or shelf at the back or side of a fireplace, used for keeping food warm." Is this a correct application for the word? If so, I would suggest replacement with a more commonly used term.

--Bagheera 23:28, 5 February 2007 (UTC)

Hob is the usual term in British English - Wiktionary doesn't seem to have it, although there is a perfectly good explanation in Wikipedia at the disambiguation page for Hob - "Hob, the top cooking surface on a cooker (referred to as a 'stove top' in the United States) in the United Kingdom, Singapore, and other parts of the commonwealth. It typically comprises several cooking elements (often four), also known as 'rings'". As the article is written in British English, it should be left that way. WLDtalk 08:52, 6 February 2007 (UTC)


 * Thanks for the clarification, but I would suggest a more descriptive (less coloquial) term. While the term "Hob" may be common to describe an electric cooking appliance in the Commonwealth, it doesn't appear to be a commonly recognized term on the Net.  If nothing else, since you refer to the disambiguation page, perhaps linking the term to that would be appropriate.  (you may already have)
 * Cheers,
 * Bagheera 22:33, 6 February 2007 (UTC)
 * Linked. Hob isn't electric cooking appliance, its any 'stove top'/'cooktop' - gas, coal, oil, wood, electric. It also listed here List_of_words_having_different_meanings_in_American_and_British_English. I'd be happy to eliminate non-American colloquialisms, if American colloquialisms were also removed.  As it is, there's an uneasy truce between writers of American English and writers of non-American English in the English Wikipedia.  I tend to view it as an opportunity to expand my vocabulary. Cheers. WLDtalk 23:42, 6 February 2007 (UTC)


 * I'm no big fan of colloquialims myself, and appreciate the added vocabulary and your link to clarification. I wonder if the term "cooking surface" is appropriately generic?
 * Cheers
 * Bagheera 20:10, 7 February 2007 (UTC)


 * To me, 'cooking surface' would imply the surface that the food is placed directly upon - like a griddle/hot plate/hibachi i.e. a heated flat metal plate on which eggs, bacon, mushrooms, etc. can be fried - often seen in British cafes and American diners. I'm not convinced we should be coining neologisms purely for Wikipedia. WLDtalk 08:54, 8 February 2007 (UTC)


 * Good point, though I'd still like to find an acceptible, generic, term to describe them in context. In this article, we're talking about generic induction cooking appliances rather than specifically a built-in device (a 'range' in US terminilogy) or a smaller portable plug-in device.  I'm sure there's a non-region-specific, technically correct, word to use here.
 * Bagheera 18:47, 8 February 2007 (UTC)

When looking at them in stores, I've always found them referred to as "cooktops" (the same as resistive electric and gas ones). A google search tends to indicate that this is a relatively common term (see, for instance) .--Eyrian 15:27, 8 February 2007 (UTC)


 * That's what I've found as well, but I understand WLD's point in the way it's written. This is a case where the common terms differ between English speaking countries.  Personal preference is to use terms that are most recognizable to the broadest range of readers.
 * Bagheera 18:47, 8 February 2007 (UTC)


 * Just to be pedantic hob in this context isn't a colloquialism; dialect perhaps...


 * In my opinion cooktop is easier to understand than hob, it's more or less self explanatory after all. I'm not from an English speaking country so maybe I can be considered unbiased. It's not particularly hard to understand the meaning of hob from the context though.
 * Apis O-tang 17:17, 6 September 2007 (UTC)


 * "Range" seems to be the generic, commercial term, though I've rarely heard it used in normal speech. Perhaps that could be used as a compromise? I prefer "stove" or "stovetop" myself.
 * Tea and crumpets (t c) 20:00, 30 November 2007 (UTC)
 * No compromise is necessary, or desirable. 'Hob' is a perfectly good English word, used extensively in many parts of the world. There is a policy on Wikipedia to keep the language variant used in the article unchanged from that chosen by the original author, or major substantive contributor, except for articles that are specific to a region where a particular language variant is used. See WP:ENGVAR and WP:SPELLING. This policy is there to prevent edit warring.  It does say that "Sensitivity to terms that may be used differently between different varieties of English allows for wider readability; this may include glossing terms and providing alternative terms where confusion may arise. Insisting on a single term or a single usage as the only correct option does not serve well the purposes of an international encyclopedia." - so the article explains what 'hob' means for people who may not be familiar with that particular word. No more is necessary. As I've said previously, reading Wikipedia articles with unfamiliar terms is a way of expanding one's vocabulary WLDtalk 21:00, 30 November 2007 (UTC)

'Range' means something quite different in British English. 'Cooktop' is far from clear. An induction hob would not normally be considered a stove or stove top here. Its a hob; sorry, but that's just what it is.

There is a simple solution for anyone that can't accept international variation: use both words and put one in brackets (parentheses). Tabby (talk) 09:06, 2 February 2008 (UTC)


 * What threw me off with the unfamiliar word "hob" was that it was in the plural "hobs" where it first appeared in the 3rd paragraph. The first two paragraphs referred to "induction cooker" singular. I have changed the 3rd paragraph to singular to improve the flow of the article and linked the word "hob" to the disambiguation page. I disagree with the idea that just because the original author used british dialect that it should be left alone and not clarified. Induction cookers are not a british only product. Encyclopedia articles for the most part should be in common language, with uncommon or technical terms explained or linked. (Do british speakers refer to "Stove Top Stuffing" as Hob Stuffing? :) Telpardec (talk) 12:18, 26 February 2011 (UTC)

not good
seems to have a lot mistakes ... --217.31.212.189 16:12, 17 May 2007 (UTC)

Possibly a typo?
"When the electromagnetic field reaches the surface of a conductive linear medium, the electric and magnetic fields lag each other by 45 degrees. "

Can someone confirm that it's not 90 degrees since the magnetic and electric components of a photon's field are orthogonal (as in right angle to each other=90 degrees). Of course they might be right. That's why I ask for someone who knows for sure.

Of course it makes sense that if they were lagging by 45 degrees, there'd also be only 180 degrees in a circle or they'de be ahead by 135 degrees. This is obviously obsurd! I'm also assuming that order doesn't matter. If it does, then of course being 45 degrees behind is the same as being 225 degrees ahead.

24.162.128.27 14:33, 18 September 2007 (UTC)

Ooops, logged in. And of course a typo - I meant 325 degrees, not 225 degrees. JWhiteheadcc 14:36, 18 September 2007 (UTC)

Can not cook solid food ?
I have been using this induction cooktop (TCL stand alone unit) for an year now. I found that You can only cook liquid or semi-liquid food but not solid. For instance if you put just potato in the pan without any liquid or water, nothing will happen; I think this is a *major* disadvantage. —Preceding unsigned comment added by 220.226.25.101 (talk) 14:37, 23 September 2007 (UTC)
 * sorry, original research charon 14:37, 1 December 2007 (UTC)

Unless its from a site, we cannot use this as source. Sorry. Ryou Hashimoto (talk) 03:07, 11 August 2008 (UTC)

Economic considerations
On the need of a citation: the 84% IH / 40% gas efficiency US Dept of energy tests results come from the referenced pdf (first in external links), but the data in that pdf need some interpreting. Also, it would be useful to specify whether the effectivity is measured from the supplied energy to the cooking dish or rather to the cooked meal itself. charon 14:37, 1 December 2007 (UTC)

There are some inconsistencies as follows:

(1) Consistency in units is key. "time required to boil 2qts water" & " energy consumption used to boil 2000 ml of water..." Don't use different sets of measurement units/quantities. Either use quarts or litres, and be sure the quantities are the same: i.e. two quarts or two litres.

(2) Under your bulleted "Efficiency", be more clear in your title: i.e. "(Stove)Efficiency". In the third paragraph, you indicate a gas burner "has about 30% efficiency AT THE STOVE", yet under the bulleted "efficiency" section you indicate a gas efficiency of 50%. Again, as mentioned in the "Question about efficiency" discussion section, the overall efficiency is the product of the various efficiencies of each stage (double check your natural gas transmission loss reference: I believe it to be more on the order of 2%).

(3) "Energy consumption use to boil...": I am assuming your energy output is from the stove itself, and overall net efficiencies are factored in?? —Preceding unsigned comment added by 204.134.212.146 (talk) 00:28, 13 December 2009 (UTC)

Price
Modification on price to $60 from personal observation in recent search for cheap induction cooker. The < $60 price tag was found in shops around Los Angeles Chinatown. A pricetag of $88 was found around Roland Heights, CA, from different brands. I just bought one in Beijing, China for $22. The brand is called Midea. Works well. —Preceding unsigned comment added by 143.239.65.80 (talk) 12:33, 7 July 2009 (UTC)

Priniple of Operation
"The pot is typically made from stainless steel or iron, which is much less conductive. This means that most of the energy will become heat in the high-resistance steel, and the driving coil will stay cool."

The resistance of a cast iron pot is lower than that of a copper wire coil, not higher. The reason for selective heating is not the resistance difference, it is the 2 facts that: Tabby (talk) 09:11, 2 February 2008 (UTC)
 * eddy currents in the iron can and do short out. If the iron were made in a similar wound insulated strip fashion to the copper coil, it would not heat due to eddy currents.
 * magnetic hysteresis does not occur in the copper as its not magnetic.
 * The resistivity of iron is certainly higher than the resistivity of copper. The correct resistance to use in a circuit model for the system is a more complex question. The DC resistance between two points on the iron pot will be low, but the AC resistance is significantly higher due to the skin effect, because of iron's high permeability. And the pot is effectively a single-turn winding, so the "transformer" steps down the voltage and steps up the current. This means that the resistance to represent the loss term get scaled up if you reflect it to the primary for analysis.
 * Hysteresis losses are a small effect; the references describe them as accounting for less than 10% of the heat, and generally neglect them in their analysis. It's important that the pot be ferromagnetic because the permeability determines the skin depth and increases the AC resistance, not because of hysteresis losses. 75.92.130.203 (talk) 05:53, 21 May 2009 (UTC)

2 Qs
"plus the same or greater degree of controllability as gas.[citation needed]"

surely anyone knows electricity can be controlled instantly at the touch of a button, does that really need citing in 2008?
 * Conventional electric elements (e.g. coils or ceramic flat-top) have a high thermal capacity, so even though you can instantly adjust the power to the element, it will take a relatively long time for the element to respond with a temperature change. (This is a major reason some cooks prefer gas over electric.) However, induction elements do not have this problem; they respond as quickly as gas. This point is worth mentioning in the article.

"In Japan, a large percentage of rice cookers are powered by induction heating."

Is that true? If so, why? Where is the advantage of (higher cost) induction over a built in fixed element? Tabby (talk) 09:11, 2 February 2008 (UTC)


 * Seems to be true (I am an anonymous living in Japan), at least for the non-budget models. By the way, this article could really use a bit more on the downsides of induction cooking. I am stuck with one of these bloody things in my kitchen and although I do enjoy boiling water in less time than it takes to put the water in the pot in the first place, not being able to use any pot or pan you want is a significant drawback. This style of cooking also lacks the feel of a gas hob and forces you to use flat-bottomed cooking ware.


 * Also, put the wrong kind of frying pan on this thing and it will leave you with a kitchen reeking of burned Teflon and a broken frying pan. —Preceding unsigned comment added by 43.244.59.254 (talk) 14:41, 12 April 2008 (UTC)

Hysteresis vs Eddy current
I thought that induction Hobs work by magnetic hysteresis losses in the pan, and that eddy-currents in the "transformer secondary" have a negligible effect. I think the article as it currently stands is wrong. I own one of these devices, and it only works with ferrous, i.e. iron or steel pans. Aluminum pans don't work at all. (I don't think Copper works either). —Preceding unsigned comment added by 87.194.171.29 (talk) 02:26, 13 April 2008 (UTC)

Hysteresis losses vs. Eddy Current (I^2*R) Heating -- Redux
There is a widespread belief that induction cookers produce substantially all of their heat from hysteresis losses in the ferromagnetic cookware, and almost none from resistive (I^2*R, Joule) heating. I don't know the source of this belief. I've seen this claim repeated in many nontechnical discussions of induction cookers, either without source or with a reference back to Wikipedia.

But this is just plainly wrong. Any technical reference will confirm that most of the heating occurs due to I^2*R losses, due to the currents induced in the resistive pan. The permeability of a ferromagnetic pan is important because of its effect on the AC resistance (gets bigger, due to the decreased skin depth) and the inductance of the system. This is the reason why copper and aluminum pans don't work. The hysteresis losses are a small effect by comparison.

I have corrected the article, and inserted references to technical notes from two manufacturers of semiconductors for induction cookers, and one IEEE journal article. If you believe this is incorrect, then please cite a reliable source (a manufacturer's technical note, an IEEE journal article, etc.) that supports you. Otherwise, please do not propagate this misperception. 75.92.130.203 (talk) 01:59, 21 May 2009 (UTC)

Question about efficiency
"currently electricity generation efficiency from coal or gas fired power plants (responsible for 80% of total electricity) is about 33%, and the energy lost during transmission is usually about 5%, therefore the overall source to food efficiency is 28%"

5% of 33% is about 1.6%, you cannot simply subtract the values correct? —Preceding unsigned comment added by 24.186.196.41 (talk) 19:59, 4 November 2009 (UTC)

Regarding the above statement: when calculating net efficiencies, one must be consistent in units: i.e. either work with all percentages transmitted, or all percentages lost. Therefore, the mathematical relationship is not "5% of 33% is about 1.6%", but 95% of 33%: you must multiply the efficiency of each stage to reach an overall efficiency. Based on the above stated reasonable efficiencies of 33% power plant efficiency and 95% transmission efficiency (5% loss), the net efficiency from power plant to stove (not necessarily "food" as stated in the text) is 0.33 x 0.95 = 0.3135, or ~31.4% efficient.

Please also note comment under "economic and environmental considerations". —Preceding unsigned comment added by 204.134.212.146 (talk) 00:11, 13 December 2009 (UTC)

improvements
I just edited a couple of statements in the article claiming that only the pot heats up. This is obviously false... unless there is absolutely no transfer of heat from the pot (the source of the heat) to the stovetop, the stovetop will heat up at least somewhat. I thought it was better to change it to say that heat is only generated in the pot (which I suspect is still a bit imprecise).

I read through the article twice and both times felt that many of the basic concepts and specific examples are repeated two or three times in the article. Some pruning is probably in order, but since I don't understand a lot of the science involved, I'd better not go mucking around. Still, there must be an upper limit to how many different ways the article should explain the heating process...

Anyway, fascinating subject. I had no idea that this technology was on the market. Thanks for educating me! Aylad ['ɑɪlæd] 18:13, 8 December 2009 (UTC)

You're absolutely right about 'only the pot heats up' something you do see quoted a lot about induction hobs. I've used one for years and of course the hob heats up when you're cooking on it, just as a work-top would if you left a pan of boiling water on it. It's true they get no where near as hot as if they were the heat source (like a halogen hob). (Twostaricebox (talk) 21:33, 16 December 2009 (UTC))

Radiation
Under "Drawbacks" appears "Anyone with a pacemaker or defibrillator should not use one of these stoves"; that, too, is incorrect. (Who wrote this stuff up?)

While anyone with such a device should seek definitive medical advice from a qualified physician, the great preponderance of the scientific evidence, which I will not attempt to summarize here (but see http://theinductionsite.com/radiation.shtml), is that there is essentially no risk.

I have modified the text accordingly. I would like to add an External Link to The Induction Site, but I well know that many Wikipedeans go postal when someone adds a link to a resource that they maintain, however good the resource may be. If someone else wants to look at it and add it, that would be nice, and quite helpful. Eric Walker (talk) 00:28, 21 January 2010 (UTC)

Question about use of glass and ceramic pots

 * "But it is not at all possible to build an induction cooker that would work with a cooking vessel made of an electrically insulating material (for example, glass or ceramic) pot."

It seems that if the food is primarily a conductive (salt) water, such as many broths or soups, that an induction oven would be able to heat it through glass or ceramic, much in the manner of a microwave oven. Is this not the case? Madkaugh (talk) 00:11, 3 February 2010 (UTC)

Why copper aluminum or even glass could work/Under what circumstances and inpracticalty
This is to answer some questions and perhaps be a place to develop a new paragraph/section for the artical. In theory there is no real reason why a induction cooker could not heat aluminum or copper pans  and 1 step further would be even food in a glass dish. Your issue here is the frequency and or intensity/concentration of the electromagenetic waves. When you say in the manner of a microwave oven your spot on, with frequencys that high even food itself can be heated by the EM waves at a reasonable intensity/concentration. The reason why most cookers wont work with copper and aluminum is because they will require a frequency/intensity leveal of EM energy inpractical for most applcations and almost all home applcations, higher intenisty more amps running in the pot, higher frequency the smaller the area they are forced to flow in so the amps are flowing thrue higher resistance. If you get the frequency to high youve changed a transformer in to a radiotransmitter and thus will not effectively induce current without a faraday cage to contain and concentrate(microwave oven box). induction melting of aluminum Eadthem (talk) 03:35, 14 February 2010 (UTC)