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Re: [TCML] IGBT paralleling
Thanks - I had my head narrowly focused on DRSSTC's and completely forgot
about the SISG. I hadn't heard much about that topic lately.
Regards, Gary Lau
MA, USA
On Sun, Jul 11, 2010 at 3:51 PM, Scott Bogard <sdbogard@xxxxxxxxx> wrote:
> 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@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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