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How to build a 1600W induction heater?

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blackwoolf511

Tue Mar 05 2013, 10:56PM

Registered Member #4278 Joined: Tue Dec 20 2011, 09:03PM
Location:
Posts: 17

Hello guys.
I was studing the mazilli driver and one thought came in my mind.
What would have to be changed to make this circuit work with 1500-1600W power current?
Is this circuit still good or it has to be a totally different circuit?
How could it be built?
Thank you all for whatever help you can give.

Platinum

Tue Mar 05 2013, 11:11PM

Registered Member #3926 Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525

Hmm I'm not quite sure myself but just increase the power of all components, and use PowerFET's, I just soldered 25N120 IGBT's to mine, So I can use my monster powersupply on it to get 700+Watts.

I think the main component would be the cap bank in the case.

blackwoolf511

Tue Mar 05 2013, 11:43PM

Registered Member #4278 Joined: Tue Dec 20 2011, 09:03PM
Location:
Posts: 17

So you are saying that by installing for example
2 x 25N120 igbt and
8 x 3.3uf cap
would be enough to have
1500-1600w of power with the same mazilli driver?
Correct me if i'm wrong.

Platinum

Wed Mar 06 2013, 01:44AM

Registered Member #3926 Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525

No I'm unsure I was just saying I use 25n120 as they are alot more powerful, and with these IGBT's you can theoretically have a Vin of 300vDC maximum. And this will push alot of power.

StormInABottle

Wed Mar 06 2013, 11:31AM

Registered Member #9252 Joined: Fri Jan 04 2013, 06:27AM
Location: Andromeda
Posts: 253

Replace 1/4 watt 10k ohms with 10 watt 10k ohms. 2 watts should be enough. But 10 watts for the safe side I am using 2 watts. but that is subject to change.[

Replace 1 or 2 watt 470 ohms. With a 2 watt 1k ohm. But i heared 470 works better. IF ya wanna stick with 470. Then increase to 5 or 10 watts. I have 40 watts. Cause i got a great deal on them.

Diodes should have no problem though.
Use high power fets. for higher voltage input dont use irfp 260 or 250.
For higher current. Get some 2 to 5 260s and parallel them. But a easier solution is just use a igbt. Beware that the circuit behavior changes with igbt bricks. So you will need more tuning and with a straight swap. Your igbt might get a bit cooked. So when just swapping mosfets with igbts. do short runs. Unless your igbts arent heating.

12 volt zenners enable a slightly higher freq
15 volt zenners enable a slightly higher current. As i read. use them more than 1 watts. 5 watts for safety. I use half a watt. But that is subject to change
And the capacitors.
The capacitors are REALLY important. I used 18 parallel series caps. And created an invincible cap.

Steve Conner

Wed Mar 06 2013, 12:34PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

The Mazzilli driver tends to be unstable at high power.

To be more precise, as soon as I*Rds(on) gets bigger than Vgs(th) minus one diode drop, which can easily happen with hot MOSFETs carrying high current, the devices won't turn off completely. This makes them start to heat up more, and as Rds(on) increases with temperature and Vgs(th) decreases, the process is self-intensifying and usually ends in MOSFET death.

Various gate drive schemes have been proposed to fix this, but at the end of the day it's as easy to just go to a half or full bridge.

Search the forum for a thread called "OMG Induction Heater" for lots more info.

Dr. Dark Current

Wed Mar 06 2013, 04:13PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Someone on the forums here, I think Roger, has done it. It works, you just need a very low ON-resistance of the transistors as you increase the power, so the on-state drop on the FETs should never increase above some 1-2 V. This basically means putting a lot of devices in parallel, decreasing the gate resistor value and using a dedicated 12-15V supply for the gates.

blackwoolf511

Thu Mar 07 2013, 10:19PM

Registered Member #4278 Joined: Tue Dec 20 2011, 09:03PM
Location:
Posts: 17

Could someone put a basic design or how it has to be modded effectively?
How many Capacitors should i use and with what power rate (example 8 x 3.3uf)?

IamSmooth

Fri Mar 08 2013, 05:11PM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

blackwoolf511 wrote ...

Hello guys.
I was studing the mazilli driver and one thought came in my mind.
What would have to be changed to make this circuit work with 1500-1600W power current?
Is this circuit still good or it has to be a totally different circuit?
How could it be built?
Thank you all for whatever help you can give.

I found that at higher powers the switches become less forgiving if your frequency dips too far below resonance. I found, after much experimenting, that the best solution for high power was controlling the frequency with a PLL and uP.

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