diode-connected transistors

[John Larkin]

Its pretty bad all right. Normally in a drive this only happens when
there is an overload. But overload ratings are a great area for
specmanship. nd you can see how its quite possible to get great overload
ratings for a while...


A lot of big IGBTs do. Semikron make a range of neat goodies. You might
want to take a look at their SemiTOP range.


These powerex die are about 1cm on a side. Conduction loss is 1200W or
so at 600A. Switching loss is a lot higher, but obviously for short
durations. And yeah, its certainly related to the size - dx/x is
constant but larger x has a correspondingly larger dx.


I've seen those sorts of silly numbers for TO220 parts with Rtheta_j_s
of 1K/W. Go figure.....mind you I once worked with a guy who had built a
25kW liquid-nitrogen cooled inverter using little FETs.

Semikron once sold us a "rupture proof IGBT package" so we smacked it
into a prototype 100kW inverter DC bus assembly and dumped a full bus
charge into it - 1.4kJ or so. It went BANG and the whole assembly jumped
a few feet in the air. So we replaced the dead-but-not-ruptured IGBT
with another one, and then sat an anvil on top of the PCB. This time the
package exploded - in front of the salesman. So much for rupture-proof

Mind you I once tested an smt 1500W TVS with a 600J pulse. There was
NOTHING left - not even the J-leads. I had covered the experiment with a
pyrex jug, and there were several distinctive splats - copper,
carbonised plastic and re-solidified silicon. The office lady was pissed
I had wrecked the jug, so I bought her a new one

Cheers
Terry

I'm gonna report you to the SPCS.

John

 

[John Smith]

Semikron once sold us a "rupture proof IGBT package" so we smacked it into
a prototype 100kW inverter DC bus assembly and dumped a full bus charge
into it - 1.4kJ or so. It went BANG and the whole assembly jumped a few
feet in the air. So we replaced the dead-but-not-ruptured IGBT with
another one, and then sat an anvil on top of the PCB. This time the
package exploded - in front of the salesman. So much for rupture-proof

Mind you I once tested an smt 1500W TVS with a 600J pulse. There was
NOTHING left - not even the J-leads. I had covered the experiment with a
pyrex jug, and there were several distinctive splats - copper, carbonised
plastic and re-solidified silicon. The office lady was pissed I had
wrecked the jug, so I bought her a new one

Cheers
Terry

You know those hocky puk thyristors in a ceramic package with thick copper
discs on each side? One of those things ruptured in a 500 KVA inverter I was
working on. A piece of the ceramic bounced off a tool box and landed on the
technician's arm right next to me. That's not the same inverter where the
capacitor bank exploded.

Oh, what fun.

John

 

[Joerg]

Hi Terry,

Thanks Jim for the idea (doh) of looking at a spice model. Its quite
complex. Does it work for inverse connections? (methinks it should)

Methinks, too. SPICE is a wonderful tool but wouldn't do much good if it
could not predict what happens when basic components enter a state that
wasn't so intended by its inventors. At least once it has shown me where
a notorious component fatigue failure came from, a spike so small that
the available equipment just couldn't display it. Check out this Agilent
EESof listing regarding reverse beta and stuff like that, 2nd section
"DC Large Signal Reverse Bias":

http://eesof.tm.agilent.com/docs/iccap2002/ic_mdl/icim014.html

Regards, Joerg