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Re: [TCML] IGBT paralleling
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@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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