Re: Long Pulse IGBT GDT design / HV-OLTC

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: sparktron01-at-comcast-dot-net 

Hi Jan
-------------- Original message --------------

 > Original poster: "Jan Wagner"
 >
 >
 > On Sun, 10 Oct 2004, Tesla list wrote:
 > >Original poster: sparktron01-at-comcast-dot-net Hi Jan
 > >
 > >Yes, I downloaded that AN today; will try to "throw together" Figure 5
 > >with IGBT's and IEEE dynamic voltage equilization circuit, and see what
 > >happens (like "run for cover!!!
 > >
 > > ;^))))
 >
 > If you use a resistor accross IGBT gate and emitter, watch out it's not too
 > small resistance, otherwise you might really have to run for cover! :)
 > Same situation if there are to be expected some heavy voltage transients
 > that might couple back to the gate signal... ;)
 > ------------------------------------------------------------
SNIPPO

The dynamic equilization network (DEN) is going to put a + equilization 
(compensation) bias on the IGBT gate unless it is hard driven OFF with 
-Vee.  So a floating drive system won't work...
     :^CCCC

The latest alternative would be use a pulse transformer + rectifier driving 
a TLP250
(up to 1.5A pulse) so with no drive pulse train (1-3 Mhz, 50%DC), Vge is biased
  -Vee.  When triggering pulse train arrives, OC is rapidly biased ON, and 
with appropriate speed up circuits will have a propogation delay of ~ 300 
nS.  If I can hold triggering within +/-250nS, the DEN will take care of 
equilization during turn on transistion (most critical).  Below is link to 
equilization circuit...

  <http://palgong.knu.ac.kr/~kimhg/High-voltage%20switch%20using%20series-connected%20IGBTs%20with%20simple%20auxiliary%20circuit.pdf>http://palgong.knu.ac.kr/~kimhg/High-voltage%20switch%20using%20series-connected%20IGBTs%20with%20simple%20auxiliary%20circuit.pdf

Will also have to scale Requilization from network, the 30K, 3K are scaled 
based on leakage currents of a 1.2kV 400A brick, my candidate device is a 
Fairchild HGTG27N120BN (1.2kV, Ic = 54A, ICM pulse 216A), with separate 
RHRG75120 Hyperfast Recovery Diodes, both in a TO247AC package.  If you 
"guess" that leakage current scales approximately linearly to Ic, I should 
be able to scale resistors by 5X (larger) and not impact circuit 
performance (more efficient though, 5W dissapation versus ~27W per switch 
level).  Rg may have to be adjusted as well.  The caveat of "don't change 
the DC bus voltage too fast" in article was also caught.  My comment is I 
need DEN critically when I'm turning the series stack on to full 
conduction, once the GE junctions are enhanced and saturated, following 
decrements will be significantly less critical (Voltage and current 
stress).  Only way to find out definitely will be to build a two level 
switch, operate at 2kV, and see what smokes (or arcs over...)

Thanks much for the links Jan, I've downloaded and put in my "literature 
search" tab
of my Excel design folder...  :^D

 > cheers,
 > - Jan
 >
 > --
 > ****************************************************
 > Helsinki University of Technology
 > Dept. of Electrical and Communications Engineering
 > http://www.hut.fi/~jwagner/ - jwagner-at-cc.hut.fi
 >
Best Regard
Dave Sharpe, TCBOR
Chesterfield, VA. USA