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.
Registered Member #17114
Joined: Sat May 11 2013, 09:01PM
Location:
Posts: 4
Hi all.
My name is Dewald, and I'm currently building my second tesla coil, this time medium sized drsstc driven by a full bridge IXGN60N60C2D1. I just fired it up for the first time yesterday evening, and the results were not too bad. I'm assuming it will improve with better tuning. Unfortunately, as I was running with some power (about 250 A peak, 350 VDC) and increasing the interrupter frequency, it suddenly stops, with the bridge shorted out.
I'm pretty sure I have a good, low inductance bridge design, with proper decoupling and plenty of TVS diodes. I'm using a UD2.5 style driver, with some phase lead, although the phase lead might not be optimally trimmed in. Resonant frequency is around 132kHz. I have 7.5 turns of copper tubing in a flat spiral coil together with 60 nF of 942C's.
What can you say from experience could be the most likely cause for the bridge death? I was sort of expecting at least 500A peak from it. Is improper tuning the culprit? Too long interrupter pulses? Too high resonant frequency? Too slow gate drive? Am I simply expecting too much from my IGBTs? I think I am starting to understand most if the system, but I don't really get the failure mechanisms.
Edit: Here is a video of the initial run, including the point where the bridge dies. No explosions, no bangs, just stops. http://youtu.be/ai5g96i3Y20
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Hi, Apart from bad layout, which you mentioned is all right, the other most common causes for IGBT failures in a DRSSTC are: -Bad gate waveform -Insufficient dead time (cross conduction) -Exceeding the Switching (turn-off) SOA which causes the IGBT to latch -Plain and simple junction overheating (by peak junction temperature), usually caused by switching losses and longer ON-times. Look the transient thermal impedance graph in the datasheet.
Registered Member #17114
Joined: Sat May 11 2013, 09:01PM
Location:
Posts: 4
Thanks for your reply Dr. Dark Current.
I am thinking that my gate drive might be a little slow. I see people are generally driving the gates up to +-24V. I am using 4 x MIC4452 (12A, 18V drivers), two for each half, at 18V. I mainly simplified the gate drive because I did not plan on driving huge IGBT bricks. Is there a great advantage in overdriving the gates in terms of switching losses?
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
People usually overdrive the gates if they plan running peak currents (much) larger than the datasheet maximum, where desaturation could happen. If the datasheet maximum is 300 amps, and you plan running on 500 amps, 18 volts on the gate is perfectly sufficient. The gate drive voltage doesn't affect switching losses much.
Registered Member #17114
Joined: Sat May 11 2013, 09:01PM
Location:
Posts: 4
Ok thanks. Do you have any guidelines about how fast the gate rise and fall times should be? I remember seeing >100ns when I last checked.
To me it sounds a bit like plain and simple overheating. It happens at higher interrupter frequencies, which means high duty cycle as the pulse width remains the same. I do know I was a bit short on heat sink compound the last time I mounted everything together...
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Yes, it could be overheating. The duty cycle in a standard DRSSTC should probably not exceed some 2%. 100 ns is from my point of view way too fast, few hundred ns should be OK (probably up to 1us for larger bricks). A too fast switching can destroy the transistors by voltage overshoot.
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.
Cause of IGBT Death
