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Re: SSgap Diagrams



Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>

Hi Marco,

Thanks for the great tip about the gate resistance.  I now think high speed
switching noise is what killed IGBT #2.  I setup to look for noise and it
was not hard to find!  Very high frequency (~4MHz) bad stuff was going on
in the turn off and on times.  I now have ended up with 680 ohms in the
gate.  This will probably be tweaked further but it eliminates all the
noise and does not seem to hurt operation.  The IGBT remains cool.  A scope
picture of the noises are at:

http://hot-streamer-dot-com/temp/GateR.jpg

The R1 (white) trance is with no gate resistance. R2 is with 100 ohms and
the top yellow trace is with 680.  The noise was not bad at low voltage but
it got super bad at higher voltages and was causing some false switching
(really bad for H bridge SMPSs ;-)) and general loss of control.  With the
680 ohm in there things are much more stable and I don't see little noise
burst in things I shouldn't.  I am sure I will have to work on this more
but you probably save me a bunch of IGBTs :-))

Cheers,

	Terry 



At 09:51 AM 3/30/2001 +0300, you wrote:
>Terry,
>
>I see you plan to use the IRG4PH50UD IGBT. I used the IRG4PH40UD and
>before having it working I filled a bean can with burned IGBTs. And
>think that my maximum current (besides spikes) was about 30A!
>To avoid you filling a trash can (sensibly bigger than a bean can, at
>least here in Finland!) with burned IGBTs I strongly recommend you to
>read my paper about problems and solutions with the Thor CCPS located at
>
>http://www.saunalahti.fi/dncmrc/papers.html
>
>Second paper from up, chapter "Problems encountered and solutions".
>You'll see you have better to use a gate resistor, etc. I suggest also
>to read as much as you can about gate drive techniques from available
>application notes.
>
>More, I think you would benefit from a simple current limiting system.
>What I have been using successfully is just a 2N2222 and a SMD (thick
>film, low value) resistor for each IGBT: that allowed me to use just ONE
>bean can. See the driver schematics in my paper, which is an UPDATED
>version of the schematics available on my web pages.
>
>Regards
>
>
>Tesla list wrote:
>> 
>> Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>
>> 
>> Hi All,
>> 
>> Since there is a lot of interest in my little solid state gap project, I
>> posted a few diagrams and schematics at:
>> 
>> http://hot-streamer-dot-com/TeslaCoils/MyCoils/SolidStateCoil/SSgap3-29-01/
>> 
>> I left out some of the plain Jane details of the controller's electronics
>> (lots of LMC555 and 74HCT stuff) since it is messy, but this will give you
>> the idea as to what it is about...  The real key is the Power_block,
>> Sync_sender, and Control_Panel stuff since that shows mostly what it is and
>> how it works.  These are still real rough but show the basics (I just
>> noticed the optical sender's logic is reversed ;-)).  I expect to be
>> putting a lot of time into this next week. ;-)))
>> 
>> Cheers,
>> 
>>         Terry
>
>-- 
>_____________________________________________________________
>
> Marco Denicolai           Senior Design Engineer 
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