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Re: [TCML] IGBT paralleling



Proper circuit design eliminates the spikes and ringing problems.

Most IGBT circuits are "pushed" a bit.  Steve Ward, at my open house, was
pushing his CM600s with up to 80 Amps RMS at 220 V input.

Dr. Resonance





On Mon, Jul 12, 2010 at 4:48 PM, John Forcina <forcijo10@xxxxxxxxx> wrote:

> 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.
>  >>>>>>>>>
> >>>>>>>>> _______________________________________________
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