Re: [TCML] IGBT paralleling

[DC Cox <resonance@xxxxxxxxxxxx>]

You really can't go wrong with the PowerEx series of IGBTs.  For a pig
powered unit I would consider the CM600s or CM1200s.  Yes, a bit expensive
but they work great and are extremely rugged due to their "trench gate"
design.

They make CM300 which work good for a coil with 4-5 ft spark, CM600, CM1200,
and for the really big monsters CM2400 (that's 2400 Volt, 2400 Amp!!).

I completed a design for a coil with a pair of CM2400s on each corner of the
H bridge.  It uses a pole xmfr to get the drive voltage up to 1,800 Volts
and runs at 60 kVA using a 50 kVA xmfr.  Coil is 49" dia. x 35 feet long.

Haven't built it yet, but hope to before I get much older.



Dr. Resonance

On Sun, Jul 11, 2010 at 11:16 AM, Scott Bogard <sdbogard@xxxxxxxxx> wrote:

> Hi John,
>        By chance is there a compiled list somewhere of "good IGBTs" that
> are used and those that aren't.  Anyway back to the original question, is it
> possible to parallel them?  Lets say for kicks I'm building a dual pig
> powered 30kVa magnifier with a LTR cap (I'm clearly not, we are talking
> theoretical here.)  Clearly the peak currents will be beyond any reasonably
> priced IGBT, is it possible to parallel lesser current units to handle the
> load, and what would that entail?  Thanks.
>
> Scott Bogard.
>
> On 7/10/2010 5:09 PM, John Forcina wrote:
>
>> Those IGBT's seem far from ideal.  The TO220 package is a very poor choice
>> as far as thermal conductivity and the datasheet says it all 0.75C/W.  You
>> will not be able to remove enough heat from the surface of the IGBT die
>> quick enough between current pulses and the device will fail.  They do not
>> have a internal anti-parallel diode so adding that externally will add to
>> the final cost also.  Not to mention doing that will add additional loop
>> area and stray inductance between units.  One more thing is the switching
>> times are surprisingly slow for that small of a unit.  td(OFF) 96ns.  It's
>> not that slow however it does seem slow for that small of a device.  I
>> have
>> seen much better overall performance from larger IGBT's.  My suggestion is
>> to just spend more money and use IGBT's that have been used and proven to
>> work in Tesla Coils time and time again.  There must be some reason that
>> we
>> all use them ;)
>>
>> On Sat, Jul 10, 2010 at 4:38 PM, Scott Bogard<sdbogard@xxxxxxxxx>  wrote:
>>
>> Interesting,
>>>        I am in the wee beginning stages of building my first SISG, and as
>>> such am in the market for IGBTs.  I found these, which look very
>>> inexpensive
>>> and have decent ratings.
>>>
>>>
>>> http://www.newark.com/fairchild-semiconductor/hgtp12n60a4/single-igbt-600v-54a/dp/90B5642
>>> My thinking is if heat is a problem or peak current, can I just parallel
>>> them?  at $1.50 a pop it seems infinitely better than 1 $18 IGBT of
>>> nearly
>>> the same ratings...  I didn't look at temperature or package information
>>> yet, so maybe there is a problem there.
>>>
>>> Scott Bogard.
>>>
>>>
>>> On 7/10/2010 8:26 AM, McCauley, Daniel H wrote:
>>>
>>> Scott,
>>>>
>>>> The electric ratings may be the same or similar, but you also have to
>>>> compare the mechanical ratings -  in particular the thermal ratings.
>>>>  This
>>>> would be junction-to-case thermal impedances etc...  The expensive IGBTs
>>>> that are commonly used in DRSSTCs are usually ISOBLOC type packages
>>>> which
>>>> excellent thermal impedances.  Compare this vs. a TO-247 package of the
>>>> same
>>>> die.
>>>>
>>>> And when comparing a TO-247 package to an ISOBLOC, keep in mind that you
>>>> STILL NEED to add a thermal insulator between the TO-247 and heatsink,
>>>> which
>>>> just makes the thermal impedance even worse.  The ISOBLOC (or SOT-227)
>>>> doesn't require a thermal interface other a small smidgeon of thermal
>>>> grease
>>>> or a graphite pad.
>>>>
>>>> Dan
>>>> http://www.easternvoltageresearch.com
>>>> DRSSTC, SSTC, Flyback, Plasma Speaker Kits
>>>>
>>>>
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
>>>> Behalf Of Scott Bogard
>>>> Sent: Friday, July 09, 2010 9:52 PM
>>>> To: Tesla Coil Mailing List
>>>> Subject: EXTERNAL: [TCML] IGBT paralleling
>>>>
>>>> Greetings all,
>>>>        So, after a bit of researching I've noticed there are IGBTs on
>>>> Newark with exactly the same ratings as some of the SSTC approved IGBTs,
>>>> but
>>>> at 1/10th the price.  What makes these others so special that they are
>>>> better, and if it is just a matter of peak current ratings, since IGBTs
>>>> are
>>>> gate driven, can we just parallel a few to get the required pulse
>>>> current
>>>> rating?  I ask because I've not heard of anybody doing this, then again
>>>> I've
>>>> only begun to research SSTC a little bit ago.  Just musing.
>>>>
>>>> Scott Bogard.
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