30 kVA Induction Heater

 by bwang
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Step 2: Words of Wisdom

cm400.jpg
cm600.jpg
cm200.jpg
The IGBTs: or "bricks", as we like to call them. They should be good for 600V (not a concern, I've never seen a brick rated under that before), at least 200A (I use 400A modules to be, safe), and more importantly, need to be fast. This is where you need to check the datasheet - IGBTs have an inherently long turn-off delay. For 65 kHz operation, rise time + turn-on delay + turn-off delay + fall time should be under 2 uS.
Bricks come in several types: single-transistor, dual transistor, 6-pack, and some rarer types such as chopper modules. Single-transistor modules are prevalent for 1200V and larger IGBTs, and have the highest thermal ratings and are the most difficult to mount. Duals (half-bridge modules) are the much easier to mount and can dissipate less. They are most common for 600V modules. 6-packs are used for 3-phase inverters, require no external power connections, and have the lowest thermal ratings.
Use what you see fit; this tutorial uses half-bridge modules.

The tank capacitor: is very very important. It handles tremendous amounts of reactive power at very high frequencies. It is absolutely essential that this part be selected appropriately. It must be a high-quality polypropylene or mica capacitor. I use giant snubber capacitors made by Eurofarad; alternatively, a series/parallel array of smaller capacitors (such as the Tesla coiler's beloved CDE942 series) should work. The ultimate capacitor, of course, is a water or conduction-cooled unit made by Celem, but such caps will run you about $150 for a 2 uF unit. You want enough capacitance to resonate with your work coil at no more than 70 kHz.
 
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asooy says: Apr 10, 2012. 1:50 PM
with the IGBT's what are you using to water cool it and what are the temps its running at? say i had a skm400gb125D it would be like 150c just from the switching at 65kh.
bwang (author) in reply to asooyApr 10, 2012. 2:06 PM
The inverter is soft-switched, so switching losses are negligible.
I used a CM400DU-12F.
asooy in reply to bwangApr 11, 2012. 12:03 PM
UCC27322 could i replace it with IXDD414YI
bwang (author) in reply to asooyApr 11, 2012. 12:06 PM
Yes
asooy in reply to bwangApr 11, 2012. 12:10 PM
k im just trying to use parts i can get from work
asooy in reply to asooyApr 23, 2012. 2:19 PM
would
FF200R12KE3
http://www.scut-co.com/maindoc/techtrade/pdevice/eupec/documents/datasheets/igbt3/FF200R12KE3.pdf
or
CM200DY-24NF http://www.platan.ru/pdf/1dist/mitsubishi/CM200DY-24NF.pdf
igbt work from what i could see i think they should.
bwang (author) in reply to asooyApr 23, 2012. 3:05 PM
yes.
asooy in reply to bwangApr 24, 2012. 2:44 PM
With the igbt/mosfet is Q1-Q4 mos fetes between the igbt's, and is there a better picture of the hook up between them.
asooy in reply to asooyApr 25, 2012. 8:58 AM
The Thick black line to 4 is that the transformer hooking to Q1-Q4 which i think are the MOSFETs then they hook to another transformer then to both IGBT's Q5-Q8
bwang (author) in reply to asooyApr 24, 2012. 3:27 PM
Can you clarify your question?
asooy in reply to bwangApr 25, 2012. 9:00 AM
The Thick black line to 4 is that the transformer hooking to Q1-Q4 which i think are the MOSFETs then they hook to another transformer then to both IGBT's Q5-Q8
asooy in reply to bwangApr 24, 2012. 2:24 PM
for the tank capacitor what is the voltage and amps, is this a 2uF or 20uF
bwang (author) in reply to asooyApr 24, 2012. 3:27 PM
3.75 uF
asooy in reply to bwangApr 25, 2012. 10:14 AM
how many amps/volts does it need to take, for the input cap what is its uF,amp,volts
bwang (author) in reply to asooyApr 25, 2012. 11:13 AM
The tank cap is a 580Vrms 152Arms poly cap.
My input cap was for 3-phase, so it is only a few hundred uF. Size your own capacitor for single-phase operation.
asooy in reply to bwangApr 26, 2012. 2:13 PM
the input cap would that be c9
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