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 #10052
Joined: Thu Feb 07 2013, 11:31PM
Location: Overland Park, Kansas
Posts: 78
I get it! Ben I appreciate your explanation, it makes sense now.
So the resistor turns the scary gate-emitter-GDT LC circuit into a damped LRC circuit, and the diode is to minimize fall times.
And the resistor value is a trade-off between rise-time and damping. That value would have to increase with increasing gate capacitance (decreasing oscillation frequencies), but coils running such large IGBT's would (hopefully) be operating at lower frequencies, and the extended rise-time would not be so large a problem.
I think I'll start with the 2W 5.1 ohm and see where that gets me.
Registered Member #7267
Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407
Just curious, are you going to use bipolar TVS from C-E? It seems the general consensus is that they are not necessary on the large bricks. Im wondering because I am also building a coil using dual module bricks and I'm wondering if I should get them.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Physics Junkie wrote ...
Just curious, are you going to use bipolar TVS from C-E? It seems the general consensus is that they are not necessary on the large bricks. Im wondering because I am also building a coil using dual module bricks and I'm wondering if I should get them.
Unless you are using some relatively large TVS, the general run-of-the-mill TVS (i.e. 1.5kW 1.5KE types) won't really do much as the energy behind the transients is much too great for these small TVS to handle. The best way to mitigate over voltage spikes on these types of circuits is simply to reduce your parasitic inductance as much as possible through the use of good layout, twisted pairs, and other methods. Keep components close together, route your plus and negative (return) planes directly on top of each other to reduce inductance (maximize coupling) and any time you have standard wire, twist together the outgoing and returns to reduce inductance.
Just remember with inductance, current does not want to stop instaneously. So if the IGBTs are conducting lots of current, and you open up an IGBT (switch OFF), the current wants to continue to flow and the inductance will develop a voltage across it (voltage spike) to keep the current flowing.
Mitigate by careful layout and also ensure you have soft switching (i.e. current is zero at switch transitions)
Registered Member #7267
Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407
EasternVoltageResearch wrote ...
Unless you are using some relatively large TVS, the general run-of-the-mill TVS (i.e. 1.5kW 1.5KE types) won't really do much as the energy behind the transients is much too great for these small TVS to handle. The best way to mitigate over voltage spikes on these types of circuits is simply to reduce your parasitic inductance as much as possible through the use of good layout, twisted pairs, and other methods. Keep components close together, route your plus and negative (return) planes directly on top of each other to reduce inductance (maximize coupling) and any time you have standard wire, twist together the outgoing and returns to reduce inductance.
Just remember with inductance, current does not want to stop instaneously. So if the IGBTs are conducting lots of current, and you open up an IGBT (switch OFF), the current wants to continue to flow and the inductance will develop a voltage across it (voltage spike) to keep the current flowing.
Mitigate by careful layout and also ensure you have soft switching (i.e. current is zero at switch transitions)
I'm using 1/8" thick aluminum bars between the IGBT's. The DC supply caps are mounted practically directly to the IGBT's which are also so close they are almost touching, so I think inductance is as low as possible. Thanks for the good info!
Registered Member #10052
Joined: Thu Feb 07 2013, 11:31PM
Location: Overland Park, Kansas
Posts: 78
The TVS diodes are actually going from gate to emitter. I believe this is to protect against spikes on the emitter that couple capacitively to the gate. (G-E capacitance)
I bought some 1.5KE30CAs.
I'm also buying some 5.1, 7.5, and 10 ohm 2W damping resistors to paralell with a schottky diode on the gate. I suppose its just a matter of scoping, trial and error. I'll start with the 5.1.
Registered Member #7267
Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407
Yup thats all good. And what I meant was TVS that are commonly used between C-E for smaller IGBT packages like the SOT-227, using 2 of 1.5KE220CA (220V) in series or a single 440V. But Like Dan said, these diodes arn't necessary nor can they handle the higher power of bricks. I was wondering because I hardly see anyone use them anymore with larger bricks IGBT's
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.
UD 2.1 DRSSTC Build
