[TCML] IGBT paralleling

Sun Jul 11 13:51:56 MDT 2010

For SISG you use high voltage, for just about everything else you don't, 
just rectified mains.  I said I wasn't actually going to do this, it's 
purely theoretical (and way out of the budget of an unemployed man...) 
Still it would be awesome!

Scott Bogard.

On 7/11/2010 3:14 PM, Gary Lau wrote:
> I'm going to bare my ignorance here.  I thought that the whole point of
> solid state TC's was that you don't need a multi-kilovolt power supply.  Are
> pole pigs really used to power these?  A _dual_ pig powered magnifier???
>
> Regards, Gary Lau
> MA, USA
>
> On Sun, Jul 11, 2010 at 12:16 PM, Scott Bogard<sdbogard at gmail.com>  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 at gmail.com>   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 at pupman.com [mailto:tesla-bounces at pupman.com] 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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