Re: [TCML] CM300 with current limiting, good, bad?

[Steve Ward <steve.ward@xxxxxxxxx>]

Hi Tom,

On Wed, Jul 29, 2009 at 1:25 PM, Tom Blitch <tab54o@xxxxxxxxxxx> wrote:

>
> I was interested in their faster performance.


They are not notably faster.


> I find it weird they don't list the exact cutoff current.


Me too, but generally this is not an issue except under short circuit
conditions (we are not using them as suggested).


> They must know that they are capable of handling more than the rated
> current for short periods.


Certainly, but the idea of the RTC is to reduce the risk of failure during a
fault condition (like a motor winding shorting to ground, or a short on the
inverter output).  As i said, and as powerex has told me directly, we are
NOT using these devices within spec (so long as you exceed the Ipk rating).


>
> They are the newer ones as well and they have the newer package types. I
> was thinking of designing some 4 layer pcb's for them to eliminate all the
> buss bars.


Not to be so pessimistic, but unless you order some specially thick copper
PCBs, you will most certainly run into thermal problems (assuming you
exploit these modules for what they are capable of).  Whether its a
over-heating PCB, or a PCB that turns into a fuse at the first sign of
trouble, i wouldnt put my bets on it.  Sure avoiding the job of making real
copper bus bars is a convenient thing, but ive tried to get by with less,
and it always failed (even using .021" thick Cu flashing as the conductor
would get burning hot, the .063" copper still gets a bit warm).


> I guess that's an invitation to  try them out with limiter still connected
> and see how they work.


Yes, of course they will work up to some point, where the RTC will try to
shunt the gate driver into the emitter.  Your gate drive may be powerful
enough to simply over-ride this, or you might find you are driving the IGBT
into de-saturation for an extended period of time and the thing goes
kaboom.  The RTC is intended to be used with gate drivers that detect their
enabling and immediately shut down the transistor (though somewhat slowly to
reduce dI/dt and resulting voltage transients).  Im at least curious to see
what you find, take care with your measurements!

Steve


>
>
> -Tom
>
> > Date: Tue, 28 Jul 2009 22:15:44 -0500
> > Subject: Re: [TCML] CM300 with current limiting, good, bad?
> > From: steve.ward@xxxxxxxxx
> > To: tesla@xxxxxxxxxx
> > CC:
> >
> > In the past i have opened those modules and snipped the bond wires to
> > disable the RTC limiter.
> >
> > Those modules are nice because they are lower ESL, and trench technology,
> at
> > the same time the thermal impedance is higher because the die area is
> > smaller.  I dont have enough test data to say whether they are as robust
> as
> > the CM300DY-24H.
> >
> > Steve
> >
> > On Tue, Jul 28, 2009 at 1:15 PM, Tom Blitch <tab54o@xxxxxxxxxxx> wrote:
> >
> > >
> > >
> > > Hey guys, Not sure what took my so long to sign up for this mailing
> list.
> > >
> > >  Anyway There a bunch of Powerex and Mitsibishi CM300Du-24F IGBT's on
> Ebay
> > > right now and I am tempted to grab a few except they are the ones with
> > > current limiting. Ive seen a few other manufacturers and models
> datasheets
> > > that say thier limiters don't limit till 5 to 6 times the rated current
> but
> > > powerex nor mitsubishi has this listed in thier datasheets.
> > >
> > > Anyone here had any experience with these? The listing is here. This
> isn't
> > > my listing by the way.
> > >
> > >
> > >
> http://cgi.ebay.com/Mitsubishi-CM300DU-24F-IGBT-Modules-300Amp-1200Volt_W0QQitemZ260360966780QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item3c9eb9127c&_trksid=p3911.c0.m14
> > >
> > > -Tom Blitch
> > >
> > > _________________________________________________________________
> > > Windows Live™ Hotmail®: Celebrate the moment with your favorite sports
> > > pics. Check it out.
> > >
> > >
> http://www.windowslive.com/Online/Hotmail/Campaign/QuickAdd?ocid=TXT_TAGLM_WL_QA_HM_sports_photos_072009&cat=sports_______________________________________________
> > > Tesla mailing list
> > > Tesla@xxxxxxxxxxxxxx
> > > http://www.pupman.com/mailman/listinfo/tesla
> > >
> > _______________________________________________
> > Tesla mailing list
> > Tesla@xxxxxxxxxxxxxx
> > http://www.pupman.com/mailman/listinfo/tesla
>
> _________________________________________________________________
> Windows Live™ SkyDrive™: Store, access, and share your photos. See how.
>
> http://windowslive.com/Online/SkyDrive?ocid=TXT_TAGLM_WL_CS_SD_photos_072009_______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
>
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla