Induction Heating

[HeXx]

Hello,
I have been reading allot lately about induction heating, and from what i understood is that it works with an alternating current passing trough a coil making the part being heated magnetic. I live in Europe so i already got an alternating current directly from the plug. Its 220 Volt 60 Hz.
For induction heating to work if i am not mistaken we need a much higher frequency at around 20-50khz. How can I make the 220V 60hz AC work at 20-50khz?
AC current from the plug works with a wave of Vmin=0 Vmax=220 i think.
For a induction heater to work would it have to be Vmin=-220 and Vmax=220?

Thank you.

 

[Raven Luni]

Trying to save money on your funeral costs? Better to go for a good old fashioned wood pyre if you want cremation

P.S. If you want to live, dont be messing with dangerous voltages and currents, especially if you dont know a basic thing like the correct frequency of the european mains systems...

 

[HeXx]

ow well, you didn't really confirm what I asked about the vmin vmax.
One thing you are right is that i have very little knowledge of electronics. (just had a basic course of electronics with only theory of electronics) as a complement of my Computer IT course but one thing I am sure, the voltage and frequency from my country wall socket is 220 to 240 volts ~ and 50-60hz

Any more info would be appreciated.
Thank you

 

[Raven Luni]

Not really meaning to sound condescending - it just gets hard to think of new ways to tell people not to go messing with dangerous amounts of electricity without a solid background in the subject. That includes me by the way (I'm just a hobbyist and know better than to mess with stuff that could kill me instantly).

Sorry - but just giving the same answer you'll get from anyone else.

 

[HeXx]

That means no one can help me on this forum?

Any way, I am trying to get information only at the moment.
Alternate current works as a wave instead of a continuous line like direct current.
For a induction coil to work it needs a wave with a frequency of about 40Khz and from what I understood the current must travel back and forth. Can you please confirm if I am right or if I am not, please correct me.

 

[duke37]

What country are you in?
The mains will NOT have a frequency of 50 to 60Hz. That will be the tolerance of some device you have found.

Induction heaters are essentially high power radio transmitters. They were usually single valve triode oscillators with the tank coil surrounding the object to be heated. The one I used many years ago ran at about 27MHz, we turned it on and off with a wooden stick 2m long - frightening! The fuses were about 1m long!

An AC current will be concentrated in the surface of a conductor, the higher the frequency, the thinner the skin. Look up skin effect.

 

[HeXx]

I live in Portugal, more specifically in Azores.
You said that induction heaters were essentially high power radio transmitters. What i read was that the coil induced a magnetic field on the metal to be heated.

 

[Laplace]

See ST Microelectronics Application Note AN2383 "A single plate induction cooker with the ST7FLITE09Y0"

http://www.st.com/internet/com/TECH...AL_LITERATURE/APPLICATION_NOTE/CD00115561.pdf

 

[duke37]

I looked up the electric supply in the Azores, it is 50Hz and is at 220V. The system is small so the frequency may vary a little.

I hadn't thought about an induction hob, this will run at much lower frequencies than what I was talking about and works because the load is magnetic, giving better coupling.

What is your application, cooking beans or casting aluminium dogs?

 

[HeXx]

Its for casting aluminium.
I have my own furnace but runs with gas and its kinda expensive and allot of heat is lost.

Most of the oscillations on the power grid here are the volts. Until last year I was only getting around 170 volts in my home. Finally they decided to build another transformer in my street and now the voltage is stable at 230.

 

[duke37]

You could try an induction hob but would need some good thermal insulation over the hob, perhaps mica sheets.

The hob will only work effectively if the load is magnetic. Iron loses its magnetism at about 770degC. This is above the melting point of aluminium so it may work. You will need an iron crucible.

It could be expensive if you break the glass top.

 

[Wrosixer]

I bought a CRO-1 from RMCybernetics for my induction heating projects (http://www.rmcybernetics.com/shop/induction-heater-circuit), it works a treat!

 

[Minder]

[QUOTE="HeXx, post: 1517655, member: 28621" I live in Europe so i already got an alternating current directly from the plug. Its 220 Volt 60 Hz.
For induction heating to work if i am not mistaken we need a much higher frequency at around 20-50khz. How can I make the 220V 60hz AC work at 20-50khz?
Thank you. [/QUOTE]

Low freq Ind heating is usually confined to Very large items of ferrous metal.
As a general rule higher freq is requires a smaller supply.
Google Royer induction heating, there are quite a few Utube videos.
http://kaizerpowerelectronics.dk/general-electronics/royer-induction-heater/
M.

 

[cjdelphi]

How it would normally work is the 240ac is rectified (300vdc) then chopped up into high frequency ac..

I am curious as to why you would want to try and kill yourself lol

(An induction cooker is about 50 bucks or so with pan)

 

[cjdelphi]

This is in Aus dollars... so about 35 usd/25 euros? No idea since the aussie dollar collapsed lol

 

[Minder]

A pan is not that useful if you want to silver solder small parts together with localized heating, or surface harden something!
M.

 

[rickselectricalprojects]

http://www.ebay.com.au/itm/1000W-ZV...-Module-20A-/361334867009?hash=item54213c8441
i have one of these, it wont melt any thing (apart from aluminum in a very small metal can) but it wont kill you

 

[cjdelphi]

Well that was my idea lol ... to not kill himself and to get an idea how they work when he opens it up (not my recommendation )

 

[rickselectricalprojects]

Well that was my idea lol ... to not kill himself and to get an idea how they work when he opens it up (not my recommendation )

i wasnt trying to steal your idea i just wanted to recommend something.
also how hard is it to turn one of those cheap induction cookers into an induction heater? do i just have to reshape the coil or do i have to fiddle with the electronics?
thanks

 

[cjdelphi]

Never said you were.... must be a lost in translation moment (as an English person "well that's my idea" or "that's the idea" just meant that's what i was thinking....