[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [TCML] IGBT paralleling

To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Subject: Re: [TCML] IGBT paralleling
From: Michael Twieg <mdt24@xxxxxxxx>
Date: Wed, 14 Jul 2010 10:10:46 -0400
Delivered-to: teslaarchive@xxxxxxxxxx
Delivered-to: tesla@xxxxxxxxxx
In-reply-to: <AANLkTil7MGwQoeNCEJKqNjalLgqarQdRPFayan-rvA8u@xxxxxxxxxxxxxx>
List-archive: <http://www.pupman.com/pipermail/tesla>
List-help: <mailto:tesla-request@pupman.com?subject=help>
List-id: Tesla Coil Mailing List <tesla.pupman.com>
List-post: <mailto:tesla@pupman.com>
List-subscribe: <http://www.pupman.com/mailman/listinfo/tesla>, <mailto:tesla-request@pupman.com?subject=subscribe>
List-unsubscribe: <http://www.pupman.com/mailman/listinfo/tesla>, <mailto:tesla-request@pupman.com?subject=unsubscribe>
References: <4C37D225.9030706@xxxxxxxxx> <4A257B3B453C8B4AA2EA143EB475F51E630A3D3E@xxxxxxxxxxxxxxxxxxx> <4C38DA46.7000903@xxxxxxxxx> <AANLkTinQfp_0YioMwC0wP6g6hilTrnWkpE3-_EalXfJC@xxxxxxxxxxxxxx> <4C39EE7A.9080806@xxxxxxxxx> <AANLkTikmrT3mtr8cMZs_Aw1WIu4gxxGRE02hmOhFX1gv@xxxxxxxxxxxxxx> <AANLkTikHycxoojoNOjX66l6OpOdQXsMPcBJWqc47oxFz@xxxxxxxxxxxxxx> <61AB156F-970C-4D09-AEE9-9B993EF131D6@xxxxxxxxx> <AANLkTiknSvyPzvybPONe0t-iY30mQnzywRHFteFWGDWE@xxxxxxxxxxxxxx> <FA1E8F8E5D884E03A57FA912DA472E28@DFNN7M91> <F763B50B-A602-435F-8F9D-1FD4A2FE4270@xxxxxxxxx> <AANLkTilq1tmjO9ALLKgYRYnZAuWBlzJE4pAmbl-5Tdyv@xxxxxxxxxxxxxx> <AANLkTil7MGwQoeNCEJKqNjalLgqarQdRPFayan-rvA8u@xxxxxxxxxxxxxx>
Reply-to: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sender: tesla-bounces@xxxxxxxxxx

Literally no amount of circuitry can eliminate ringing and spikes due to a
device's internal inductance.  The actual collector of the device is not
accessible to protection circuitry (unless you plan on tearing off the case
and soldering directly to the die).

And "pushing" current is very different from pushing voltage.  The current
ratings for IGBTs are given under the assumption that they are being hard
switched, which causes far more power dissipation than if they were soft
switched.  That's why the current ratings can be pushed so far for tesla
coil bridges.  It's not that the manufacturers are being conservative with
their ratings (they have no incentive to do so), it's that we're not
operating them in a typical fashion.

Unlike the current ratings, the voltage ratings can't be pushed.  It's a
pretty hard limit which is independant of what load you're driving.  If you
try to operate your bus voltage above those ratings, they will fail very
quickly.  And any sane engineer will give at least 25% headroom on the bus
voltage (much more if they don't have very good snubbers).

-Mike

On Tue, Jul 13, 2010 at 10:23 PM, DC Cox <resonance@xxxxxxxxxxxx> wrote:

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

Follow-Ups:
- Re: [TCML] IGBT paralleling
  - From: Steve Ward

References:
- [TCML] IGBT paralleling
  - From: Scott Bogard
- RE: [TCML] IGBT paralleling
  - From: McCauley, Daniel H
- Re: [TCML] IGBT paralleling
  - From: Scott Bogard
- Re: [TCML] IGBT paralleling
  - From: John Forcina
- Re: [TCML] IGBT paralleling
  - From: Scott Bogard
- Re: [TCML] IGBT paralleling
  - From: Gary Lau
- Re: [TCML] IGBT paralleling
  - From: DC Cox
- Re: [TCML] IGBT paralleling
  - From: Drake Schutt
- Re: [TCML] IGBT paralleling
  - From: DC Cox
- RE: [TCML] IGBT paralleling
  - From: Brian
- Re: [TCML] IGBT paralleling
  - From: Drake Schutt
- Re: [TCML] IGBT paralleling
  - From: John Forcina
- Re: [TCML] IGBT paralleling
  - From: DC Cox

Prev by Date: Re: [TCML] New coil modeled after Green Monster
Next by Date: Re: [TCML] New coil modeled after Green Monster
Previous by thread: Re: [TCML] IGBT paralleling
Next by thread: Re: [TCML] IGBT paralleling
Index(es):
- Date
- Thread