-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Post it online somewhere if you can and I'll review it as well.
- From your scope image, I'd say it looks like you may have some grounding issues with your 'scope probe (as Gene mentioned, use a direct ground from the probe tip to a ground "local" to the signal you're probing...ideally within a cm or so), in addition to possible other problems. The over-shoot and under-shoot (ringing) are likely caused either by your scope probing techniques, by the signal transition speed, or possibly both. If better probe grounding still shows the ringing, you should try fix it...a couple possible options are: * Slow down the turn-on and turn-off transition times of your power devices, reducing di/dt. Note that this increases the time spent in the linear region, increasing power dissipation. * Add or improve the protection devices clamping over- and under-shoot, typically something like a high speed TVS zener diode. As for the second 'runt' pulse you're seeing, I suspect this is caused by your drive circuit...my first guesses would be magnetic feedback from the switched current or ground transients between the driver logic and the IGBT power devices, but without a circuit diagram and maybe a picture of the installed wiring, I'm just guessing. On 2/10/2013 7:40 PM, Leonardo Marsaglia wrote: > Hello Gene, and thanks for your answer. > > I have the circuit in PDF format, would you like me to send it to > you so you can see it? > > 2013/2/10 Gene Heskett <[email protected]> > >> On Sunday 10 February 2013 19:01:08 Leonardo Marsaglia did >> opine: Message additions Copyright Sunday 10 February 2013 by >> Gene Heskett >> >>> Hello Andy. >>> >>> http://imagebin.org/246204 >>> >>> Here's a picture of what I scoped the other day, this is the >>> signal coming out from the IC's that we use to fire the igbt's, >>> as you can see those spikes are a little dangerous I think. >> >> First, I am a CET, and a retired (mostly) broadcast engineer. >> >> 2nd, Correct, both the spikes, and all that racket on the falling >> edge bothers me, a lot. >> >> First on the overvolt spikes, I'd make sure the scope ground is >> floating so that you can attach it to the circuits common. They >> may not be near as pronounced if a ground loop is eliminated. >> >> 2nd, that double or triple shuffle on the falling edge isn't at >> all good. Its needless switching and heating in the >> transistors./ >> >> Perhaps the grounding and supply bypassing are both suspect. I'd >> check to see what effect a .1 paper/mylar capacitor across the >> buses might indicate poor bypassing. >> >> Do you have a URL to that circuit? I'll take a look at it if I >> can. >> >>> I've talking a lot with Tim and he's a great help, he's always >>> helping me with his advices and knowledge. >>> >>> About using an arduino or fpga, I've been thinking about that >>> too, I need to catch on with VHDL since I've only made some >>> simple counters and multiplexers but I really like the idea of >>> make a whole system from an fpga. >>> >>> Anyway, the main problem here is after the firing IC's since >>> the oscilator is generating a perfect square wave form. >>> >>> >>> 2013/2/10 andy pugh <[email protected]> >>> >>>> On 10 February 2013 22:15, Leonardo Marsaglia >>>> >>>> <[email protected]> wrote: >>>>> based on DIY circuits found on the internet. >>>> >>>> I guess you have seen: >>>> http://webpages.charter.net/dawill/tmoranwms/Elec_IndHeat1.html >>>> >>>> (Lots of clever stuff, much better done in software now) >>>> >>>>> Anyway, the real deal here is always how to have a clean >>>>> square signal to fire the igbt's. >>>> >>>> Sounds like a job for Arduino or FPGA. I can't help feeling >>>> that there ought to be a suitable Mesa module, but Arduino's >>>> have PWMs that share a clock, so for suitable thresholds are >>>> guaranteed not to overlap. I don't know how smoothly you can >>>> change frequency >>>> >>>> -- atp If you can't fix it, you don't own it. >>>> http://www.ifixit.com/Manifesto >>>> >>>> >>>> ---------------------------------------------------------------------- >>>> >>>> - -------- Free Next-Gen Firewall Hardware Offer >>>> Buy your Sophos next-gen firewall before the end March 2013 >>>> and get the hardware for free! Learn more. >>>> http://p.sf.net/sfu/sophos-d2d-feb >>>> _______________________________________________ Emc-users >>>> mailing list [email protected] >>>> https://lists.sourceforge.net/lists/listinfo/emc-users >> >> >> Cheers, Gene -- "There are four boxes to be used in defense of >> liberty: soap, ballot, jury, and ammo. Please use in that >> order." -Ed Howdershelt (Author) My web page: >> <http://coyoteden.dyndns-free.com:85/gene> is up! My views >> <http://www.armchairpatriot.com/What%20Has%20America%20Become.shtml> >> >> It matters not whether you win or lose; what matters is whether I I win or >> lose. -- Darrin Weinberg I was taught to respect my elders, but >> its getting harder and harder to find any... >> >> >> ------------------------------------------------------------------------------ >> >> Free Next-Gen Firewall Hardware Offer >> Buy your Sophos next-gen firewall before the end March 2013 and >> get the hardware for free! Learn more. >> http://p.sf.net/sfu/sophos-d2d-feb >> _______________________________________________ Emc-users mailing >> list [email protected] >> https://lists.sourceforge.net/lists/listinfo/emc-users >> > > > - -- Charles Steinkuehler [email protected] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (MingW32) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iEYEARECAAYFAlEYUIAACgkQLywbqEHdNFz0cQCgy6iQtoj5/hNB17ibXrGKW2gG k08AoMQ0kIfj1eAVjc5so84SbimjMCVo =Y0Io -----END PGP SIGNATURE----- ------------------------------------------------------------------------------ Free Next-Gen Firewall Hardware Offer Buy your Sophos next-gen firewall before the end March 2013 and get the hardware for free! Learn more. http://p.sf.net/sfu/sophos-d2d-feb _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
