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RE: [TCML] IGBT paralleling
OK I see what you guys are talking about, I guess it helps to read all the
posts before adding anyting, as long as the IGBT's are kept withing spec
there should be no problem, I have used the TO247 style with pretty good
results with 120V Vac RMS into a doubler and they have no problem, the TO220
style I have not used. I do know for sure is thay you need some pretty beefy
rectifiers as I have taken several of those out when trying to use the TO220
style cases, they just give up the ghost in a really pretty flash and a few
flames :) even when I slowly ramped up the voltage the smaller TO220 case
rectifiers could not deliver, however I have not cooked one TO247 style. The
longest I let the coil run is around 10 minutes or so but everything is
still in great shape.
The IGBT's are of the TO247 case style as well, I have never seen these
particular IGBT's as ever being used in a tesla appication so I was not
really sure what to expect my orignal thoughts were they would not do well
but they have done suprising well and I get around 35 to 36 inches of spark
when run with 120Vac and a doubler Circuit.
Some ringing in the intial design caused one of them to burn out but after
the ringing was eliminated they have been performing really well over the
last year or so.
Each has its own heat sink and I do have a fan on them but I am not sure if
the fan is needed or not I have not checked the operating temperature on
them but after running for around 10 or 15 minutes they feel warm but not
hot. The best thing about them is they are cheap around $3 or $4 a piece.
I do have pictures if anyone wants to to see them I can post them I have
pics of the coil running so you can see the distance I am getting, nice
bright white sparks, I have not run this coil outside so I am not sure what
max spark length is But I think around 3 feet is going to be the limits on
this design.
-----Original Message-----
From: David Sharpe [mailto:sparktron01@xxxxxxxxx]
Sent: Sunday, July 11, 2010 9:09 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] IGBT paralleling
Drake
The "headroom" DC is referring to is the voltage of the IGBT's, versus
applied DC to the IGBT's. There is a cautionary warning here for the causal
Power Electronics developer. If insufficient headroom is allowed between
operating DC and IGBT DC (CBO max + transient
overshoot) can result in sudden device failure. Further, if you run more
then 75% of device maximum ratings as DC applied can result in the dreaded
SEBO (Single Event Burn-out) failure.
The "Single Event" alluded to above is ionizing radiation in the form of
random Cosmic Radiation, which can result in catastrophic avalanche failure
of the device.
The first generation French TGV Electric Traction Locomotives exhibited
frequent failures that were finally determined to be caused by this
phenomenon. It has likewise been determined that ionizing radiation
including energetic neutrons can precipitate this type of failure.
http://www.smpstech.com/power-mosfet-single-event-burnout.htm
http://www.boeing.com/assocproducts/radiationlab/publications/Neutron-Induce
d_Single_Event_Burnout_in_High_Voltage_Electronics.pdf
http://en.wikipedia.org/wiki/Single_event_upset
http://www.spaesrane.com/html/downloads/SMITHS_GE_Aviation.pdf
Google "Single Event Burnout" and over 100k hits will be presented. Also if
one studies the last pdf/ppt by GE Aviation, note the admonition on page 14
and I am quoting:
"When applied voltage is >200V, use 50% de-rating to protect against SEB(O)
/ SEGR".
Also of note; all industrial Variable Frequency Drives, Induction Heaters,
and solid state power devices which I have used or applied in my career use
1.2kV devices for 480VAC 3ph systems (~600VDC pk), and 600V devices for
240VAC (~300VDC pk). This is in full agreement with the above design
factoid.
You may elect to "push" the ratings of your solid-state devices in your
particular application, but you do so at your device and systems PERIL.
Regards
Dave Sharpe, TCBOR/HEAS
Chesterfield, VA. USA
On Sun, Jul 11, 2010 at 5:13 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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>>>>
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--
Dave Sharpe, TCBOR/HEAS
Chesterfield, VA USA
Sharpe's Axiom of Murphy's Law
"Physics trumps opinion!"
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