Thank you all for the inputs! I didn't even think about checking out ebay.
I looked last night and they were about $50 per module. I was hoping to
reuse my current SG coil and modify it for solid state operation, so I
guess I should measure the current resonant frequency to make sure it isn't
too high. Is 100 kHz the upper limit for the CM300 or is it more of a soft
limit where performance diminishes over 100 kHz?
One other question that is kind of related to this topic...how is the main
power supply for the system designed? I have seen a lot of variations using
either 120VAC input or 240VAC input with mentions of using a voltage
doubler and the like. Are there any design guides out there for this
subject including what full wave rectifier to use and the size of the
capacitors that are needed for a given supply output?
Again, thank you all for the help!
Jeremy
On Monday, July 7, 2014, Steve Ward <steve.ward@xxxxxxxxx> wrote:
> Jeremy,
>
> Most DRSSTC builders go to ebay to find used IGBT modules for TC use, this
> is why the CM300DY-24H became so popular, they have been on the surplus
> market steadily for years. When they first hit ebay i was buying them for
> just $10 each, but now days expect to pay about $50 per module. They are
> considerably slower switching than the APT module so you would likely want
> to keep the TC resonant frequency <100khz. I should also note that the
> CM300 appears to be one of the most rugged "300A" modules ever, they just
> dont make them like that anymore. Nowdays, IGBT manufacturers are claiming
> higher current ratings on less Si, and that means we cant abuse the parts
> as much.
>
> The only drawback to using the compact H-bridge module is cooling it. The
> higher density of components makes it more difficult to remove the heat.
>
> Half-bridge does work fine for driving a TC, of course you only get half
> the voltage out. Some people prefer having less parts and like half-bridge
> for that reason. I think the advantage of higher drive voltage is the main
> reason to go H-bridge, twice the power at the same current.
>
> If you want to start small and relatively cheap, i really like the
> FGH60N60SMD. Its a very fast part, i use it up to 400khz. I would suggest
> keeping the peak current to just 200A, and if you need more you can
> parallel them. Id also suggest a seperate heatsink for each transistor so
> that you dont have to use electrical isolation between the transistor and
> the heatsink (heatsinks would be live).
>
> I like to use EEM.com and octopart.com to source IGBTs, i often find
> distributors that i've never heard of that sell these parts in larger
> quantities, but less $/part than digikey and mouser.
>
> Steve
>
>
> On Mon, Jul 7, 2014 at 9:01 AM, Jeremy Gassmann <jeremyee78@xxxxxxxxx
> <javascript:;>>
> wrote:
>
> > Yeah, I definitely noticed the price tag. But comparing that to the
> > CMM300 half bridge, it is on par with the price and it is all integrated
> > into one package which I would think would help reduce parasicitcs. I
> guess
> > this begs the question: what is the advantage of doing a half bridge
> versus
> > a full bridge? I would assume that it would be higher power but I am
> still
> > learning power electronics (I'm an RF engineer).
> >
> > I was also thinking that this part would kind of be one to grow
> > into...basically I could start by running it way backed off (lower
> voltage
> > and current) and reduce the chance of destroying it. That way I could
> learn
> > with reduced risk of a costly mistake. Then once I am comfortable I can
> > upgrade the power supply around it. Are these sound strategies to use or
> do
> > IGBTs like to be driven more toward their limits? Thanks for the response
> > and insight!
> >
> > Jeremy
> >
> > On Monday, July 7, 2014, Steve Ward <steve.ward@xxxxxxxxx <javascript:;>>
> wrote:
> >
> > > Jeremy,
> > >
> > > The APTGLQ200H120G part looks outstanding, and the price tag matches
> > that.
> > >
> > > Assuming you use a good driver that switches the IGBTs right near the
> > zero
> > > crossing in primary current, they should be capable of driving a fairly
> > > large tesla coil. Id suggest operating within the 770A spec on the
> > parts,
> > > but at 600V thats quite powerful. Provided they have good cooling, one
> > of
> > > these parts could probably drive a 5-10kW coil.
> > >
> > > There really isnt an "Fmax" for a part, its a continuous curve of
> > > "operating current vs frequency". Id suggest running at <100khz if you
> > > really want to push the peak current level to the max, but they would
> > still
> > > work fine at less peak current and a higher frequency.
> > >
> > > Steve
> > >
> > >
> > > On Sun, Jul 6, 2014 at 9:52 AM, Jeremy Gassmann <jeremyee78@xxxxxxxxx
> <javascript:;>
> > > <javascript:;>>
> > > wrote:
> > >
> > > > Hello everyone. I am starting my journey on the DRSSTC road and have
> > some
> > > > questions regarding the heart of the system...the IGBT. There are a
> lot
> > > of
> > > > options out there including half bridge packages and even full bridge
> > > > packages. Looking at the data sheets shows a lot of characteristics
> > such
> > > as
> > > > input and output capacitance, rise and fall times, and switching
> > energy.
> > > My
> > > > question is: what are the most important factors to look at when
> > > selecting
> > > > a device? Obviously current and voltage ratings are very important
> but
> > > what
> > > > about keeping capacitance as low as possible, etc? Are there any good
> > > > documents out there the correlate these parameters to an fmax of the
> > > > device?
> > > >
> > > > I did find a device that looks like it would be a good candidate: the
> > > > Microsemi APTGLQ200H120G. It is a full bridge power module. Anyone
> work
> > > > with this device or know if there any reasons not to use it? Thank
> you
> > > all
> > > > very much for the help!
> > > >
> > > > Jeremy
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