Induction heating
Penguin7471, Mon May 22 2006, 12:37PMI recently modified my old ignition coil driver and hooked up a small work coil to it to try out induction heating for fun. The work coil is some random 16 gauge wire, ~40 turns.
With 24V input, at ~3A, output freq ~300kHz, I can get a 1.5cm long, 0.5cm diameter steel thread to red hot within about half a minute.
Uhm, is this bad, good, or...? I have no idea how efficient the setup is, so I was wondering if any of you experienced induction heaters could offer any advice? Sorry, if it weren't for the lack of fresh batteries for the camera...
Re: Induction heating
c4r0, Mon May 22 2006, 02:59PM
This is my setup made today:
It takes about 15sec @ 100V 1A power supply to get this result:
Freq is 270kHz and the screw is about 5mm diamerter just like your object. I'm not sure is it good result neither, but i think it can't be bad to get a screw red with only 100W of power
c4r0, Mon May 22 2006, 02:59PM
This is my setup made today:
It takes about 15sec @ 100V 1A power supply to get this result:
Freq is 270kHz and the screw is about 5mm diamerter just like your object. I'm not sure is it good result neither, but i think it can't be bad to get a screw red with only 100W of power
Re: Induction heating
Penguin7471, Tue May 23 2006, 05:42AM
Ah, very similar results to mine.
My O'scope isnt working, so I just tune the frequency until the current draw is minimal, this seems to provide maximum heating transfer to the steel. Is this how you tuned yours, or am I just strange?
Penguin7471, Tue May 23 2006, 05:42AM
Ah, very similar results to mine.
My O'scope isnt working, so I just tune the frequency until the current draw is minimal, this seems to provide maximum heating transfer to the steel. Is this how you tuned yours, or am I just strange?
Re: Induction heating
c4r0, Tue May 23 2006, 08:16AM
I'm tuning my stuff using o-scope connected to transformer's primary or measuring work coil current (my poor self-made current transformer shows about 30Arms in resonance). But in my case current draw is the biggest in tune (as i said before 1 - 1.5A from 50-100V)
When it is not tuned current is very small, about 100mA. Hmmm ....
This is a schematic:
And this is today's morning result
c4r0, Tue May 23 2006, 08:16AM
I'm tuning my stuff using o-scope connected to transformer's primary or measuring work coil current (my poor self-made current transformer shows about 30Arms in resonance). But in my case current draw is the biggest in tune (as i said before 1 - 1.5A from 50-100V)
When it is not tuned current is very small, about 100mA. Hmmm ....This is a schematic:
And this is today's morning result
Re: Induction heating
Wilson, Tue May 23 2006, 09:25AM
Just in case you haven't already previously seen, here's my thread outlining my prototype 2kW induction heater.
Heating iron is quite easy due to hysteresis losses, the trick is to have the coupling between the work coil and the workpiece as high as possible.
75VA to get iron glowing within 30secs isn't bad. from memory, it took me 10secs to heat up a similar object with 200W.
Wilson, Tue May 23 2006, 09:25AM
Just in case you haven't already previously seen, here's my thread outlining my prototype 2kW induction heater.
Heating iron is quite easy due to hysteresis losses, the trick is to have the coupling between the work coil and the workpiece as high as possible.
75VA to get iron glowing within 30secs isn't bad. from memory, it took me 10secs to heat up a similar object with 200W.
Re: Induction heating
Maz, Wed May 24 2006, 12:58AM
this is quality suff guys, i wish i knew more about it.
Maz, Wed May 24 2006, 12:58AM
this is quality suff guys, i wish i knew more about it.
Re: Induction heating
Simon, Wed May 24 2006, 02:05AM
Simon, Wed May 24 2006, 02:05AM
Maz wrote ...
this is quality suff guys, i wish i knew more about it.
Then do a web search or ask a specific question here.this is quality suff guys, i wish i knew more about it.
wrote ...
E. Make sure each post has a point. Unless you're in the chatting board, there's no need for a one-liner post that doesn't have any real content. Save the one-liners and offhanded comments for private messages.
E. Make sure each post has a point. Unless you're in the chatting board, there's no need for a one-liner post that doesn't have any real content. Save the one-liners and offhanded comments for private messages.
Re: Induction heating
Hazmatt_(The Underdog), Wed May 24 2006, 06:36AM
That's really great!
A friend showed me how to tap off of the AC on a SMPS. And I can tell you that it takes a while to get red hot even with 800W behind the coil! So you really got it!
I'm going to get away from using a SMPS and do it right. At the time I needed a demo quick for the college open house.
Next step, reduce 3/8 nuts to a molten mass! hehehe
Hazmatt_(The Underdog), Wed May 24 2006, 06:36AM
That's really great!
A friend showed me how to tap off of the AC on a SMPS. And I can tell you that it takes a while to get red hot even with 800W behind the coil! So you really got it!
I'm going to get away from using a SMPS and do it right. At the time I needed a demo quick for the college open house.
Next step, reduce 3/8 nuts to a molten mass! hehehe
Re: Induction heating
Wilson, Wed May 24 2006, 08:21AM
good luck! Be sure to try heating non-ferrous metals as well as ferrous. Its quite a challenge to melt anything non ferrous.
Wilson, Wed May 24 2006, 08:21AM
good luck! Be sure to try heating non-ferrous metals as well as ferrous. Its quite a challenge to melt anything non ferrous.
Re: Induction heating
Bored Chemist, Wed May 24 2006, 06:27PM
"Its quite a challenge to melt anything non ferrous."
I'd start with gallium
Bored Chemist, Wed May 24 2006, 06:27PM
"Its quite a challenge to melt anything non ferrous."
I'd start with gallium
Re: Induction heating
Simon, Thu May 25 2006, 12:33AM
That bolt is seriously hot but way off from melting. I'd guess about 700C (check a colour chart) - you'd need to get into the thousands to melt iron.
I'm sure Hazmatt knows that very well but just in case anyone missed the joke.
Gallium. Hmm, that might be a little easier.
Simon, Thu May 25 2006, 12:33AM
That bolt is seriously hot but way off from melting. I'd guess about 700C (check a colour chart) - you'd need to get into the thousands to melt iron.
I'm sure Hazmatt knows that very well but just in case anyone missed the joke.
Gallium. Hmm, that might be a little easier.
Re: Induction heating
c4r0, Thu May 25 2006, 02:37PM
This is two of my last photos:
a bearings ball and a steel screw
According to this chart
it seems to be >1000*C on the edges, can it be true? 
whoa
c4r0, Thu May 25 2006, 02:37PM
This is two of my last photos:
a bearings ball and a steel screw
According to this chart
it seems to be >1000*C on the edges, can it be true? whoaRe: Induction heating
Steve Conner, Thu May 25 2006, 06:44PM
c4r0, I'm just wondering why did you choose to parallel feed the tank circuit? I tried the exact same setup, and an almost identical matching transformer, but I used a series feed to the tank. And the weird thing is, it worked about as well as yours :-/
My heater drew 7A at 30V and its performance was limited by the tank capacitors getting too hot.
http://scopeboy.com/elec/induction/
Steve Conner, Thu May 25 2006, 06:44PM
c4r0, I'm just wondering why did you choose to parallel feed the tank circuit? I tried the exact same setup, and an almost identical matching transformer, but I used a series feed to the tank. And the weird thing is, it worked about as well as yours :-/
My heater drew 7A at 30V and its performance was limited by the tank capacitors getting too hot.
http://scopeboy.com/elec/induction/
Re: Induction heating
Penguin7471, Fri May 26 2006, 07:07AM
c4r0... WOW! Nice work... is that still at the same input power?
Here are some of my objects... there is a large airgap between work coil and item because I wanted to be able to try many different metal things.
From top to bottom.. a weird hex nut/screw, a thin bolt, and a steel thread (actually one of my coilgun projectiles)
Penguin7471, Fri May 26 2006, 07:07AM
c4r0... WOW! Nice work... is that still at the same input power?
Here are some of my objects... there is a large airgap between work coil and item because I wanted to be able to try many different metal things.
From top to bottom.. a weird hex nut/screw, a thin bolt, and a steel thread (actually one of my coilgun projectiles)
Re: Induction heating
c4r0, Fri May 26 2006, 11:00AM
) and i'm keeping voltage under 100V and current draw under 1,5A.
I thought that parallel circuit will draw the smallest current from secondary winding in resonance (with the biggest current in tank circuit at the same time) , in contrast to serial circuit (the biggest current through primary in resonance).
This is my coil with capacitors.
The capacitors doesn't get too warm. But the coil is soldered to caps and after about 30s of work the tin melts (becouse the coil gets red hot) and the coil comes off
I saw induction heater on your site, and actually i took the idea of using a transformer in my circuit from there I was amazed how it can work so well without a heatsink on mosfets.
c4r0, Fri May 26 2006, 11:00AM
wrote ...
is that still at the same input power?
Yes, max 150W. I'm using a fullbridge made of irf820's (very cheap is that still at the same input power?
) and i'm keeping voltage under 100V and current draw under 1,5A. wrote ...
c4r0, I'm just wondering why did you choose to parallel feed the tank circuit? I tried the exact same setup, and an almost identical matching transformer, but I used a series feed to the tank. And the weird thing is, it worked about as well as yours :-/
My heater drew 7A at 30V and its performance was limited by the tank capacitors getting too hot.
Actually i don't know c4r0, I'm just wondering why did you choose to parallel feed the tank circuit? I tried the exact same setup, and an almost identical matching transformer, but I used a series feed to the tank. And the weird thing is, it worked about as well as yours :-/
My heater drew 7A at 30V and its performance was limited by the tank capacitors getting too hot.
I thought that parallel circuit will draw the smallest current from secondary winding in resonance (with the biggest current in tank circuit at the same time) , in contrast to serial circuit (the biggest current through primary in resonance).This is my coil with capacitors.
The capacitors doesn't get too warm. But the coil is soldered to caps and after about 30s of work the tin melts (becouse the coil gets red hot) and the coil comes off
I saw induction heater on your site, and actually i took the idea of using a transformer in my circuit from there
I was amazed how it can work so well without a heatsink on mosfets.Re: Induction heating
Wilson, Fri May 26 2006, 11:13AM
Nice work c4r0. I think the >1000 temp is accurate enough. Those metal parts look just like the coins which i was heating just before they were about to melt.
You might want to invest in some thin copper tubing to make a water cooled work coil for longer runs
Wilson, Fri May 26 2006, 11:13AM
Nice work c4r0. I think the >1000 temp is accurate enough. Those metal parts look just like the coins which i was heating just before they were about to melt.
You might want to invest in some thin copper tubing to make a water cooled work coil for longer runs
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