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what mosfet to use for an induction heater

danadak

Feb 19, 2021
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Use MOSFET to do what ? What are the ratings of the induction heater you are
trying to design. Your schematic.....?

Google "induction heater schematic", plenty of circuits with part numbers.


Regards, Dana.
 

hevans1944

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what mosfet to use for an induction heater
I favor thermionic power tetrode or power pentode forced-air cooled vacuum tubes for high-frequency induction heaters. I did have some experience working with a low-frrequency, inducution-heated, pressure welder installed in a high-vacuum chamber at the General Electric Evendale Plant sometime in the previous century. At that time GE was interested in constructing integrated, monolythic, blade-to-shaft turbine assemblies, what they called a Blisk. Catchy name, huh?

Most jet engines have turbine blades assembled onto a disk (the central shaft) with threaded fasteners that secure individual blades into dove-tail cutouts. This disk has cooling passages machined therein to cool the turbine blades, which themselves have hollow passages through which cooling air can be passed. All this requires a level of precision unheard of in internal combustion engine technology. Manufacturing and attaching the turbine blades to the disk was (and perhaps still is) very time-consuming and labor intensive. The goal of the project was too assemble a blade to the disk by heating the blade to a controlled temperature only slightly less than the melting temperature of the titanium alloy from which he blade was machined. Sort of a putty-like consistency. With everything at the proper temperatures, the turbine blade was forced against the disk and thereby welded to it. GE called this machine a pressure welder, but there are variations on the theme that use mechanical friction to heat parts to be pressure welded, mostly rod-shaped parts that could be rotated at high velocities and then pressed together end-to-end. I didn't much get involved with friction pressure welding.

GE used very low frequency induction heating because they needed fast and deep penetration of the heat. Higher frequencies didn't penetrate as well because of "skin effect". Anyhoo, we never had any problems with the low-frequency induction heater. I was there to help solve problems with the hydraulic servo that pressed the two parts together to form a weld. Closure rate was very important because the turbine blade immediately began to cool as soon as it was removed from the induction heater electro-magnetic field. Depth of penetration was also very important since we wanted all the turbine blades to be at the same height from the disk. If everything went according to plan, techs from GE inserted a turbine blade, clamped an induction heating coil around it, closed up the vacuum chamber, and cyrogenically pumped it down to a "pretty good" vacuum. After heating the turbine blade to a fiery yellow, the hydraulic piston pushed it down into the disk. BLINGO! A Blisk is Born! Well, after attaching a few dozen more turbine blades of course. Fascinating process to watch, but wait! There's more:

There was a considerable amount of "flash" generated in the welding process. Across the hall from this pressure welder was a glass-enclosed robot equipment room. The robot took the final Blisk assembly and machined off the flash, leaving a compressor assembly ready for installation in the next generation of aircraft powered by GE turbofan engines.

So, as @danadak suggested in his post #2 above, we need a little more information before we can make any suggestions. You may be just a one-time "drive by" poster who is only looking for a quick answer. Not finding one, you move on to another forum. Well, I have a quick answer for you: use a 2N7000 mosfet. If that works for you, please reply back here with pictures and the schematic you used to assemble your induction heater. We are here to help!
 

roughshawd

Jul 13, 2020
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Get one that is not effected by field radiation. Some new transistors are designed to fire when a field is a certain strength.

heat is often produced by humoring the professor...
 

hevans1944

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Induction heating is not complicated. You create a high-powered sinusoidal wave form at a certain frequency. Couple this wave form to an induction coil, wound in such a shape as to enclose the part to be heated. Depending on the power produced, it may be necessary to use a coil made from hollow copper tubing with a closed-loop water cooling system. Insert the part to be heated so that it is centered within the coil. Make sure the load (coil with part to be heated) is matched to the wave form source (a "tuning" network is often used, but this depends on the design of your induction heater), and then increase the power to the level necessary for heating to occur.

Induction heating only works with parts that are susceptible to heating by eddy currents induced at the frequency selected. Since there are quite a few things that do not efficiently absorb electro-magnetic energy in this manner, they are "induction heated" indirectly by inserting the part to be heated inside a susceptor, usually a high-temperature nickel alloy. The alloy become incandescent as it is heated by induction. The part inside becomes heated by radiation emitted from within the internal walls of the susceptor, as well as by conduction if there is a tight fit between the susceptor and the part being heated.


I notice that induction heating cook tops are becoming popular. I would love to have one of those, but I have heard they work best with cast iron skillets. Or do induction heating stove tops require special pots and pans and skillets? It has been asked before, but I will ask again: What are you trying to DO?
 

73's de Edd

Aug 21, 2015
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Get one that is not effected by field radiation. Some new transistors are designed to fire when a field is a certain strength.

roughshawd . . . . . . .

You do be one . . . . . " wild and CRAZY guy " . . . . . with uber emphasis being placed on the CRAZY aspect.
 

Harald Kapp

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Get one that is not effected by field radiation. Some new transistors are designed to fire when a field is a certain strength.
Do you have a link to valid information that supports your assertion?
 

hevans1944

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Do you have a link to valid information that supports your assertion?
What?! You want the poster to present with objective and verifiable FACTS with a link to VALID information? Or as Homer Simpson once said, "Facts, shmacks. You can prove ANYTHING with FACTS! Facts are meaningless. You could use facts to prove anything that's even remotely true.”

Well, I am not a Homer Simpson fanboy, and I never saw the cartoon episode where he allegedly said something like that, but that is obviously how some people on this forum attempt to assess reality.

Harold, our gentle German moderator, obviously doesn't understand woo-woo "science" at all! :eek:This is almost as bad as @73's de Edd bashing the poor little ol' 2N7000 mosfet that I INSANELY suggested the OP try to use to make an induction heater. Clearly, I was mistaken there. A 6L6GC power pentode will fly rings around the puny 2N7000. It can also be wired up for use as a guitar amplifier. And it is pretty much radiation tolerant (any bandwidth, any wavelength, dc to light) for use in high-fluix field radiation environments. Very surprised NASA hasn't "re-discovered" the solid-state (no moving parts) technology of beam-power electron vacuum tubes... especially since their "speciality" is SPACE wherein lots of "hard" vacuum resides.

Ah, well... since the OP hasn't responded with our requests for more information, and in lieu of my making anymore INSANE suggestions, I hereby suggest that a moderator close this thread, and allow us to move on to the next hot topic: How to Achieve World Peace BEFORE using nuclear weapons.:D
 

bertus

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Nov 8, 2019
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Hello,

Have a look at the attached Zip-file with an overview of the IRF mosfets.

Bertus
 

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hevans1944

Hop - AC8NS
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Hello,

Have a look at the attached Zip-file with an overview of the IRF mosfets.

Bertus
Wonderful! I don't know how you find the time to dig out this information, but it is much appreciated. Can you now attach a Zip-file to your next message that contains all the power IGBTs that might be useful? @ramussons suggested this in post #4 but nobody responded.
 

bertus

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Hello,

Here is an overview from Rohm on IGBT's .

Bertus
 

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hevans1944

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Hello,

Here is an overview from Rohm on IGBT's .

Bertus
Thanks!

@bertus has provided us with minimal datasheets describing the latest and greatest power metal-oxide-semiconductor-field-effect-transistors (MOSFETs) as well as datasheets describing the latest and greatest insulated-gate-bipolar-transistors (IGBTs). That should give the OP, @ahmed ragab ahmed, plenty of devices to choose from so he build an induction heater. Glad we could help with that. Well, @bertus helped... not too sure about the rest of us.
 

danadak

Feb 19, 2021
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A quick and dirty way of part selection go to digikey, and use the filter controls
to filter to package, various voltages (threshold, breakdown), currents, and then
pick a couple of datasheets to look at. This way you know production status as well,
even inventory level at digikey. Generally speaking large inventory indicates popular
part as well as bigger customer base. Generally speaking that is, there is/are always
exceptions.


Regards, Dana.
 

hevans1944

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Gee, whiz, folks. I completely forgot to check into which forum the OP asked their question! The Electronics Homework Forum, of course. We ARE NOT supposed to give definitive answers to questions asked there. Guidance and pointers to the right direction ONLY!

So, forget 2N7000 mosfets, 6L6GCs power tetrode vacuum tubes, or any of a plethora of high-power MOSFETs (or IGFETs) and IGBTs. Forget about parametric searches on DigiKey or other distributors. Just forget any suggestions made here with regard to specific devices, circuits, best wiring practices, selection of components, yada, yada, yada. You will only need those later if you actually decide to build an induction heater. What you need to do NOW is make Google your best friend to help you research "the how and the why" of induction heaters, "the when and the where" high-frequency, mid-frequency, and low-frequency induction heaters are best used.
 

ramussons

Jun 10, 2014
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I notice that induction heating cook tops are becoming popular. I would love to have one of those, but I have heard they work best with cast iron skillets. Or do induction heating stove tops require special pots and pans and skillets?
Induction heating "cook tops" are very common in this country for more than a decade.
There are 2 requirements for the vessels being used - Physical shape and material used.
Physically, the vessel must be Flat Bottom'ed spanning the coil area. If the spanned area reduces, the heat generated also reduces.
The material need not be magnetic. The electrical conductivity matters. Good conductors / Insulators are a No No. So, no silver, copper, Ceramic, Plastic.... The material commonly used is Stainless Steel - a whole lot of kitchen utensils are made from this. Cast iron skillets with a flat bottom. Pressure cookers made of aluminium have a special sandwiched bottom.
The best part of this "stove" is that you can remove the cooking vessel without switching OFF the stove. No vessel, no heating, no power drawn. And the heating / power drawn also depends on the coil area spanned.
 

Keonte45

Aug 29, 2022
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Gee, whiz, folks. I completely forgot to check into which forum the OP asked their question! The Electronics Homework Forum, of course. We ARE NOT supposed to give definitive answers to questions asked there. Guidance and pointers to the right direction ONLY!

So, forget 2N7000 mosfets, 6L6GCs power tetrode vacuum tubes, or any of a plethora of high-power MOSFETs (or IGFETs) and IGBTs. Forget about parametric searches on DigiKey or other distributors. Just forget any suggestions made here with regard to specific devices, circuits, best wiring practices, selection of components, yada, yada, yada. You will only need those later if you actually decide to build an induction heater. What you need to do NOW is make Google your best friend to help you research "the how and the why" of induction heaters, "the when and the where" high-frequency, mid-frequency, and low-frequency induction heaters are best used.
So, if one actually wants to build an induction heater what's the best to use? 2N7000 mosfets or 6L6GCs power tetrode vacuum tubes?
 

hevans1944

Hop - AC8NS
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As before mentioned, this is the ELECTRONICS HOMEWORK HELP forum. Specific solutions to questions are verboten here!

You are welcome to start a NEW thread in a DIFFERENT forum, but please do some research first. Find out how commercial induction heaters are built, their power requirements, and their frequency of AC excitation (obviously an induction heater cannot be operated with DC excitation). The POWER ELECTRONICS forum might be an appropriate place to start your new thread.
 

Harald Kapp

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So, if one actually wants to build an induction heater what's the best to use? 2N7000 mosfets or 6L6GCs power tetrode vacuum tubes?
The question is not which component is "best" for an induction heatre. Ther question should center around the requirements for the component in terms of e.g.;
- voltage
- current
- frequency
- power dissipation
- etc.

@ahmed ragab ahmed : Is this really a homework or schol assignment related question? If so, Hop is absolutely right: YOu will receive guidance, but so complete solution. If not tell us what your question is about (repair? construction? or whatever) so I can move the thread to the matching forum.
 
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