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 #1617
Joined: Fri Aug 01 2008, 07:31AM
Location: Adelaide, South Australia
Posts: 139
(In a seperate thread because they are a bit different)
My My current TC (incomplete) uses a bridge of hgtg40n60a4, which are the TO-247 ones without the internal diode. So obviously, I will have external freewheel diodes, in the form of u8100e diodes. I have also changed my mind, and want to put some tranzorbs there as well (better to be safe than sorry, the price of a tranzorb is less than an IGBT), but I was thinking, is this even a good idea?
During the conduction of the free wheel diodes, if I use unidirectional tranzorbs, are they likely to become foward biased? The data sheet for the 1.5ke series seems to indicate they have a slightly lower foward voltage curve than the u8100e diodes. Is this likely to be a problem? Whats the reverse recovery of a tranzorb like?
Also, am I right in assuming that the 'working voltage' rating is the nominal reverse voltage? So if i have a 340v supply, the 1.5ke440a (working voltage 342v, clamping voltage 548v and the max voltage of the 40n60a4 is 600v) will be the one to use?
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
From memory; this type of igbt will act pretty much like a TVS once it's Vce rating is exceeded, so if a TO247 on a heatsink can't dissipate transients, an axial diode package certainly will not. My guess is that any marginal benefit of using TVSs everywhere would probably be outweighed by potential new problems. (e.g. TVSs going short-circuit) I often use TVSs but they aren't a cure-all. IF the bus is low esr/esl etc then the freewheel diodes together with the bus act as 'spike' absorbers. Low inductance H-Bridge layout is worth researching.
Registered Member #1617
Joined: Fri Aug 01 2008, 07:31AM
Location: Adelaide, South Australia
Posts: 139
Thanks for the info, but i found some bidirectional tvs' anyway, even though its true that they shouldnt need to be used, its only a couple of dollars. I've found that even though MOSFETs and IGBTs should undergo break down and clamp voltage them selves, Ive had many mosfet deaths (IRFP460s) that certainly werent due to over dissipation (they were cold), and at the time i did notice quite a bit of ringing, so I put that down to overvoltage. You are right, they SHOULD clamp the voltage automatically and absorb the transient, but it seemed that it wanst happening that way. I dont know a huge amount about IGBTs, and how well they respond to overvoltage, so I put tvs' in anyway.
Registered Member #1232
Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881
> IF the bus is low esr/esl etc then the freewheel diodes together with the bus act as 'spike' absorbers. Low inductance H-Bridge layout is worth researching.
Yep, I'll second that. Choose the right switches and free-wheel diodes, and do a good job of the layout. Leave the TVS's for things like surge protection on power and data cables.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Sulaiman wrote ...
From memory; this type of igbt will act pretty much like a TVS once it's Vce rating is exceeded, so if a TO247 on a heatsink can't dissipate transients, an axial diode package certainly will not. My guess is that any marginal benefit of using TVSs everywhere would probably be outweighed by potential new problems. (e.g. TVSs going short-circuit) I often use TVSs but they aren't a cure-all. IF the bus is low esr/esl etc then the freewheel diodes together with the bus act as 'spike' absorbers. Low inductance H-Bridge layout is worth researching.
Sulaiman, I appreciate what you've pointed out here. For a beginner like myself, it's all too easy to get carried away with enthusiasm for a particular component or circuit configuration, and I'm sorry if I gave others the impression that TVS diodes alone would solve all their spike and surge problems, which they certainly will not.
I should have written something like "for the forseeable future, TVS diodes are likely to remain an important element in any portfolio of surge and spike mitigation strategies."
Registered Member #1617
Joined: Fri Aug 01 2008, 07:31AM
Location: Adelaide, South Australia
Posts: 139
Sulaiman, I appreciate what you've pointed out here. For a beginner like myself, it's all too easy to get carried away with enthusiasm for a particular component or circuit configuration
Haha, dont worry Harry, it wasn't you who pushed the idea into my head! I had actually been thinking about it from the start.
I do realise that low inductance layout etc are the best solution (treat the cause rather than the symptoms), and I have made an effort to build a low inductance bridge and I realize that tvs are somewhat of a 'bandaid' solution. But I figured it wouldn't hurt to put them in 'just in case', not as the primary way of removing spikes, but as a last resort. Anyway if they do cause problems such as going short circuit (but then agian, jsut about any component could do this and wreak similar havoc), I can easily pull them out.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Frosty90 wrote ...
Sulaiman, I appreciate what you've pointed out here. For a beginner like myself, it's all too easy to get carried away with enthusiasm for a particular component or circuit configuration
Haha, dont worry Harry, it wasn't you who pushed the idea into my head! I had actually been thinking about it from the start.
I do realise that low inductance layout etc are the best solution (treat the cause rather than the symptoms), and I have made an effort to build a low inductance bridge and I realize that tvs are somewhat of a 'bandaid' solution. But I figured it wouldn't hurt to put them in 'just in case', not as the primary way of removing spikes, but as a last resort. Anyway if they do cause problems such as going short circuit (but then agian, jsut about any component could do this and wreak similar havoc), I can easily pull them out.
Cheers, Jesse
Hello Jesse!
you've hit the nail on the head for me, here! The thing is to design the circuits so they'll cruise effortlessly along without ANY transient protection, and then and only then add the TVS diodes/ MOVs/spark gaps as a probablistic safety feature.
Thanks for pointing out the way to better, cleaner design!
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.
Some more TVS questions
