[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
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-Induced_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-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.
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> Tesla mailing list
>>>>>>> Tesla@xxxxxxxxxx
>>>>>>> http://www.pupman.com/mailman/listinfo/tesla
>>>>>>> _______________________________________________
>>>>>>> Tesla mailing list
>>>>>>> Tesla@xxxxxxxxxx
>>>>>>> http://www.pupman.com/mailman/listinfo/tesla
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>>
>>>>>> Tesla mailing list
>>>>>> Tesla@xxxxxxxxxx
>>>>>> http://www.pupman.com/mailman/listinfo/tesla
>>>>>>
>>>>>> _______________________________________________
>>>>>
>>>>> Tesla mailing list
>>>>> Tesla@xxxxxxxxxx
>>>>> http://www.pupman.com/mailman/listinfo/tesla
>>>>>
>>>>> _______________________________________________
>>>>
>>>> Tesla mailing list
>>>> Tesla@xxxxxxxxxx
>>>> http://www.pupman.com/mailman/listinfo/tesla
>>>>
>>> _______________________________________________
>>> Tesla mailing list
>>> Tesla@xxxxxxxxxx
>>> http://www.pupman.com/mailman/listinfo/tesla
>>>
>> _______________________________________________
>> Tesla mailing list
>> Tesla@xxxxxxxxxx
>> http://www.pupman.com/mailman/listinfo/tesla
>
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
>
--
Dave Sharpe, TCBOR/HEAS
Chesterfield, VA USA
Sharpe's Axiom of Murphy's Law
"Physics trumps opinion!"
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla