Welcome
Username or Email:

Password:


Missing Code




[ ]
[ ]
Online
  • Guests: 24
  • Members: 0
  • Newest Member: omjtest
  • Most ever online: 396
    Guests: 396, Members: 0 on 12 Jan : 12:51
Members Birthdays:
All today's birthdays', congrats!
Plasmana (31)
porkcake (52)


Next birthdays
03/20 Paul I (37)
03/20 Sigurthr (38)
03/21 Dr Who (40)
Contact
If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.


Special Thanks To:
  • Aaron Holmes
  • Aaron Wheeler
  • Adam Horden
  • Alan Scrimgeour
  • Andre
  • Andrew Haynes
  • Anonymous000
  • asabase
  • Austin Weil
  • barney
  • Barry
  • Bert Hickman
  • Bill Kukowski
  • Blitzorn
  • Brandon Paradelas
  • Bruce Bowling
  • BubeeMike
  • Byong Park
  • Cesiumsponge
  • Chris F.
  • Chris Hooper
  • Corey Worthington
  • Derek Woodroffe
  • Dalus
  • Dan Strother
  • Daniel Davis
  • Daniel Uhrenholt
  • datasheetarchive
  • Dave Billington
  • Dave Marshall
  • David F.
  • Dennis Rogers
  • drelectrix
  • Dr. John Gudenas
  • Dr. Spark
  • E.TexasTesla
  • eastvoltresearch
  • Eirik Taylor
  • Erik Dyakov
  • Erlend^SE
  • Finn Hammer
  • Firebug24k
  • GalliumMan
  • Gary Peterson
  • George Slade
  • GhostNull
  • Gordon Mcknight
  • Graham Armitage
  • Grant
  • GreySoul
  • Henry H
  • IamSmooth
  • In memory of Leo Powning
  • Jacob Cash
  • James Howells
  • James Pawson
  • Jeff Greenfield
  • Jeff Thomas
  • Jesse Frost
  • Jim Mitchell
  • jlr134
  • Joe Mastroianni
  • John Forcina
  • John Oberg
  • John Willcutt
  • Jon Newcomb
  • klugesmith
  • Leslie Wright
  • Lutz Hoffman
  • Mads Barnkob
  • Martin King
  • Mats Karlsson
  • Matt Gibson
  • Matthew Guidry
  • mbd
  • Michael D'Angelo
  • Mikkel
  • mileswaldron
  • mister_rf
  • Neil Foster
  • Nick de Smith
  • Nick Soroka
  • nicklenorp
  • Nik
  • Norman Stanley
  • Patrick Coleman
  • Paul Brodie
  • Paul Jordan
  • Paul Montgomery
  • Ped
  • Peter Krogen
  • Peter Terren
  • PhilGood
  • Richard Feldman
  • Robert Bush
  • Royce Bailey
  • Scott Fusare
  • Scott Newman
  • smiffy
  • Stella
  • Steven Busic
  • Steve Conner
  • Steve Jones
  • Steve Ward
  • Sulaiman
  • Thomas Coyle
  • Thomas A. Wallace
  • Thomas W
  • Timo
  • Torch
  • Ulf Jonsson
  • vasil
  • Vaxian
  • vladi mazzilli
  • wastehl
  • Weston
  • William Kim
  • William N.
  • William Stehl
  • Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Forums
4hv.org :: Forums :: Projects
« Previous topic | Next topic »   

Induction heater (featuring my new PLL driver :-O)

1 2 3 4  last
Move Thread LAN_403
uzzors2k
Sat Jul 12 2008, 07:05PM Print
uzzors2k Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
Originally I just bought a bunch of el-cheapo foil caps from ebay on impulse with the intention of trying the LCLR topology again. It worked somewhat with a simple TL494 inverter, but I had to constantly adjust the frequency by hand to keep the capacitor voltage safe or current draw under control. All it would have taken was one slip and the bridge or tank capacitor would die. Meh. And I hadn't even gotten to tuning the matching inductor yet.

1215889058 95 FT0 Current Pllih Setup

So I started designing a driver based on frequency adjustment to regulate the tank voltage, inverter current or inverter/tank phase. Which ever had the highest priority. (The discussion took place silently in this thread.) It would be nothing new actually, as this type of driver has been done before only with discretes. Link2 Tim's IH is complicated as hell though, and I wasn't going for something that elaborate. So after many different versions I eventually got something which worked and was reasonably simple. Behold.

1215889058 95 FT0 Ets 4046 Ih 1215889058 95 FT0 Etih Driver Board

As Richie has detailed on his site the LCLR arrangement presents a capacitive load below resonance and inductive above resonance, with inductive reactance being the most forgiving for a square wave inverter. Therefor an increase in supply current or tank voltage brings the VCO frequency up. On either side of resonance the impedance of the LCLR circuit increases, lowering current draw and resonant rise. With low supply voltages or proper loads neither the tank voltage nor the inverter current will need regulation, in which case the driver must lock onto the exact resonant frequency of the LCLR circuit for max efficiency and power. The PLL takes care of this by adjusting the VCO frequency to the point where the inverter output and tank voltage are 90 degrees out of phase (inverter leading the tank voltage), because this phase difference characterizes resonance in a LCLR circuit.

1215889058 95 FT0 Perfect Autotuned Phase Lock

How does it work in the real world? Excellently. With light to no load the voltage or current protection kicks in and keeps the inverter from self destructing. With moderate to heavy loads the PLL kicks in and keeps everything in resonance. I've run it several times over the last few weeks and haven't noticed any odd behaviour yet. The only thing I dislike is that the voltage/current regulation isn't "smooth" but seems to oscillate somewhat. It's hard to explain but you can hear white noise whenever the regulation kicks in. Hasn't caused any noticeable problems though.

Anyway with the new driver finally done I can continue working on the LCLR topology. Atm I've narrowed the limiting factor down to the matching inductor which heats up fast. Before I can do any serious heating I need to make something more robust. Currently the inductor sports 16-filar 0.3mm litz wire, which I thought would be good for 20A at 100kHz. Hence the surprise when it started heating so badly. Is there nothing more to do than wind more litz wire or get copper strips? How does one make a power inductor?

1215889058 95 FT0 Matching Inductor
Back to top
Firefox
Sat Jul 12 2008, 08:24PM
Firefox Registered Member #1389 Joined: Thu Mar 13 2008, 12:50AM
Location: Pittsburgh, PA
Posts: 346
I don't know if this is practical, but you could cut some Al flashing into a proper width strip, and turn your matching inductor from that. As I understand it, Aluminum has a larger skin depth than copper, so it may be better in this situation, and the surface area will effectively give you a larger conducting area. Also, the windings may have enough surface area to dissipate generated heat better than the 16 filar litz wire you have.
Back to top
GeordieBoy
Sat Jul 12 2008, 08:33PM
GeordieBoy Registered Member #1232 Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881
Sounds good Uzzors - I'm glad you got the controller working well.

The noise you noticed during current-limiting could be due to instability in the current control loop. Or it might be the sign of a potentially damaging low-frequency resonance between the bridge's DC blocking capacitor and the Lmatch inductor. (The DC blocking cap and Lmatch inductor will series resonate at a lowish frequency. Any control loop oscillation around this frequency is BAD!)

Re: Power inductor design, i'd use a large Mn/Zn ferrite E-core set, gapped and wound with litz. ETD and EC cores are designed to minimise the mean turn length and volume of ferrite, which is fine for a transformer, but it is not really what is wanted here. Power electronics books should cover the magnetics design.

-Richie,
Back to top
uzzors2k
Sun Jul 20 2008, 08:42AM
uzzors2k Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
I decided to make another 16-filar litz wire and wind it bifilar with the old one. About two meters of 32 strands of 0.3mm wire, wrapped around the second largest core I have. It's DC resistance is only 8.5mΩ, so it shouldn't dissipate more than a few watts.

1216543037 95 FT49746 New Matchin Inductor

I also doubled up the IRFP450s which reduced power dissipation considerably. With a single fan the inverter can run continuously I believe. Now if only the tank could do the same. The capacitors don't get warm themselves, which isn't bad considering how cheap they were. They do heat up from the immense heat conducted by the work coil though, an insulating crucible would help.

1216543037 95 FT49746 Completed Inductionh Pll

And some mandatory pics of redhot iron. The power of this IH isn't very impressive IMO, but at least it worked as a test bed for my new driver.

1216543037 95 FT49746 Nutandbolt Ih Pll 1216543037 95 FT49746 Flatheadbolt Ih Pll 1216543037 95 FT49746 Warm Nutandbolt Ih Pll
Back to top
Experimentonomen
Sun Jul 20 2008, 09:52AM
Experimentonomen Registered Member #941 Joined: Sun Aug 05 2007, 10:09AM
Location: in a swedish junk pile
Posts: 497
I saw you on youtube yesterday, i´ve also melted salt.

Add water cooling to your work coil and it will stay nice and cool and keep your tank cap from melting.
Back to top
Experimentonomen
Sun Jul 20 2008, 09:52AM
Experimentonomen Registered Member #941 Joined: Sun Aug 05 2007, 10:09AM
Location: in a swedish junk pile
Posts: 497
If you want you can also add separate water cooling to the tank cap.
Back to top
GeordieBoy
Sun Jul 20 2008, 12:36PM
GeordieBoy Registered Member #1232 Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881
Water cooling of the work coil is essential otherwise it will eventually melt from the hundreds of amps passing through it. As you found it is also subject to the radiant heat of the workpiece too, if there is no thermal "lagging" to insulate the two.
Back to top
Marko
Sun Jul 20 2008, 01:16PM
Marko Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Hi Uzzors,

Your work is awesome so far, get the water cooling running so you can ramp it up!

What I'm worried about is very poor heatsinking of your mosfets, and with sil pads, you really need far better if you want to push the little mosfet's limits. Your current heatsink doesn't look like good but for 20..30W of total dissipation.


As you are in any case going to use water cooling, could you make some sort of water blocks for each of those mosfet's - some copper pipe soldered to a copper block would probably be just fine for ~100W of dissipation per mosfet... When properly cooled I think a H bridge of IRFP450's might produce up to 3kVA. Only an estimation with my current experiences though, and not sure how much kW will that actually be in an LCLR IH.

Of course you must not use sil pads, mosfets need to be clamped to blocks directly and insulation provided by long plastic water pipes.

Cooling is one of most important things in power electronics, which many people completely underestimate and then wonder why do their semiconductors die.



Back to top
Experimentonomen
Sun Jul 20 2008, 01:22PM
Experimentonomen Registered Member #941 Joined: Sun Aug 05 2007, 10:09AM
Location: in a swedish junk pile
Posts: 497
is CPU/GPU waterblocks for pc enuf to cool a fet in a config like this ? If yes it would be a great deal since pc water cooling stuff is getting cheap nowdays, and i have some pc wc components, from hdd coolers to cpu/gpu water blocks to pumps and dedicated fluid and radiators.
Back to top
ben106
Tue Oct 21 2008, 10:12AM
ben106 Registered Member #1374 Joined: Tue Mar 04 2008, 04:14PM
Location: Switzerland
Posts: 10
Hi,
I just discovered the website of your project : great, exactly what I need ! I'll try to build someting very similar to yours.

For the matching inductor that heats, have you tried an air-core coil ? 45uH is easily feasible, I think. (I was also never really successful at induction heating, so maybe I'm wrong..)
Back to top
1 2 3 4  last

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob

Go to:

Powered by e107 Forum System
 
Legal Information
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.