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Re: [TCML] IGBT paralleling
Apparently so. I would like to see how DC will be able to get away with
this with these mysterious IGBT's because if he claims they are rated at
2400V and 1650*1.414=2333.1v that gives almost zero headroom for voltage
spikes ringing etc...
It is pretty much impossible to make a bus layout that can accommodate these
igbt's. Even with a very low inductance laminated layout the sheer slow
switching speed will create large switching spikes and will lead to a
certain death to the igbt's. Not to mention, any decent power engineer will
know to de-rate the igbt's by several hundred volts to accommodate for this
and also because it's just good practice.
On Mon, Jul 12, 2010 at 1:12 PM, Drake Schutt <drake89@xxxxxxxxx> wrote:
> So DC you're saying that you raise AC voltage to 1.7kV before
> rectification?
>
> Sent from my iPhone
>
>
> On Jul 12, 2010, at 9:08 AM, "Brian" <brianv@xxxxxxxx> wrote:
>
> Hmmm Im a little confused, 2400 vdc IGBT is the handling voltage of the
>> device , once an IGBT is on...it is on, I am not sure what this wasted
>> head
>> room is all about. Once the miller capacitance is overcome the IGBT is
>> considered on and now connects the rail voltages. Whether it is big
>> voltage
>> or little voltage it don't matter. If you wish to drive them hard at full
>> rated with 2400Vdc then drive them hard if you wish not too then don't. I
>> am
>> not sure where the idea came in that there is a bunch of wasted head room
>> that has to be filled...maybe I am missing something in this dialogue
>> somewhere...
>>
>> -----Original Message-----
>> From: DC Cox [mailto:resonance@xxxxxxxxxxxx]
>> Sent: Sunday, July 11, 2010 6:27 PM
>> To: Tesla Coil Mailing List
>> Subject: Re: [TCML] IGBT paralleling
>>
>> With a 2,400 VDC IGBT, running it at a line doubled 220 VAC gives 2400 VDC
>> -
>> 616 VDC --- over 1,784 Volts of wasted headroom that needs to be filled,
>> hence the use of a power transformer to boost the AC input from 220 to
>> around 1700 VAC. The headroom I'm referring to is similar to your audio
>> reference only in this case wasting AC power headroom on a large IGBT that
>> should be driven at higher potential to maximize coil output.
>>
>> This is, of course, all not relevant with standard medium size coils using
>> rectified line drive (such as CM300 circuits) or line rectified drive with
>> a
>> voltage doubler circuit common with CM600 IGBTs.
>>
>> D.C. Cox
>>
>>
>>
>>
>> On Sun, Jul 11, 2010 at 4:13 PM, Drake Schutt <drake89@xxxxxxxxx> wrote:
>>
>> Dc- what do you mean when you refer to headroom in this post? I'm
>>> used to the term only in music production referring to dB.
>>>
>>> Regards
>>> Drake
>>>
>>>
>>> On Jul 11, 2010, at 3:22 PM, DC Cox <resonance@xxxxxxxxxxxx> wrote:With
>>> CM300s or CM600s you can just double the 220 VAC line to get 642
>>>
>>> VDC
>>>
>>>> for a good match.
>>>>
>>>> If running, perhaps, a CM2400, you want to go up to near 2,400 VDC on
>>>> the drive, so you end up using a 220/480 Volt 3 phase to get up to at
>>>> or near the 2,400 VDC rectified. This gives you better output
>>>> because you go from
>>>> 642 VDC to 2400 VDC that is being switched into the primary inductor.
>>>>
>>>> Typically, with really large systems the only way to get from 220/440
>>>> VAC to produce the 2400 VDC drive max is to use a small 25 to 50 kVA
>>>> xmfr (surplus pole units).
>>>>
>>>> Not a dual pole pig unit, just a 220/440 VAC 3 phase xmfr delivering
>>>> around 1650 VAC before rectification.
>>>>
>>>> The main point with large DRSSTC type coils is efficiency ---
>>>> eliminating all those losses in the heat & UV light production in the
>>>> spark gap, and obtaining quicker dI/dt rates.
>>>>
>>>> As you pointed out small and medium size coils run just fine without
>>>> using any pole xmfrs. Usually above 15-18 ft long sparks the pole
>>>> xmfr boost helps out get to the higher potential of the larger IGBTs
>>>> without wasting a lot of headroom.
>>>>
>>>> Dr. Resonance
>>>>
>>>>
>>>>
>>>>
>>>> On Sun, Jul 11, 2010 at 2:14 PM, Gary Lau <glau1024@xxxxxxxxx> 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-igb
>>>>> t-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.
>>>>>>>>>
>>>>>>>>> _______________________________________________
>>>>>>>>> Tesla mailing list
>>>>>>>>> Tesla@xxxxxxxxxx
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>>>>>>>>> _______________________________________________
>>>>>>>>>
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>>>>>>>>>
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