Online source for high power MOSFETs and FETs?

[Robert Wolcott]

Anyone know of an online supplier for high power transistors?

Thanks,
Bob

 

[Walter Harley]

Anyone know of an online supplier for high power transistors?

Can you be more specific? All the major online suppliers (Newark, Futurlec,
Digikey, Mouser, Allied, ...) carry plenty of high-power transistors; is
there something in particular that you're not able to find?

Profusion PLC (in the UK, but ship to the US with no problem) supply Hitachi
MOSFETs that can be hard to find elsewhere.

 

[Robert Wolcott]

The transistors in question are:

IRFP32N50K, IXTH30N50, IXTM24N50,IXTM21N50, IRF460, IRFP460

They are used in an argon laser power supply. Any transistor that
would
function in a switchmode power supply would suffice I guess. I'm a
mechanical engineer so this stuff is a bit fuzzy to me.

Thanks,
Bob

 

[Walter Harley]

The transistors in question are:

IRFP32N50K, IXTH30N50, IXTM24N50,IXTM21N50, IRF460, IRFP460

They are used in an argon laser power supply. Any transistor that
would
function in a switchmode power supply would suffice I guess. I'm a
mechanical engineer so this stuff is a bit fuzzy to me.

Ah, you're building the circuit at
http://perso.wanadoo.fr/redlum.xohp/switchmode.html?

It looks like any of those would do, according to the author, or anything
else better than 500V and 20A. The IRFP460 is available from Digikey for
under $2 each, but they've got a handling fee if you order less than $25, if
I remember. The ST Micro STP20NM50 is available from Mouser for under $3
and would also do.

As the author suggests, you should order some extras in case you blow 'em up
during development.

 

[Robert Wolcott]

Walter,
Thanks for the reply. This is what I really need to accomplish:

http://oregonstate.edu/~wolcottr/Switching supply outline.jpg

Do you have an idea what the components for this would cost? I am designing
a 20 watt copper halide laser as a senior project. I could probably get
some help from the EE department with design but cost is a concern. Do you
have experience with this sort of thing? I would be able to build the
transformer as well, I think.

Thanks,
Bob

 

[Walter Harley]

Walter,
Thanks for the reply. This is what I really need to accomplish:

http://oregonstate.edu/~wolcottr/Switching supply outline.jpg

Do you have an idea what the components for this would cost? I am
designing a 20 watt copper halide laser as a senior project. I could
probably get some help from the EE department with design but cost is a
concern. Do you have experience with this sort of thing? I would be able
to build the transformer as well, I think.

Thanks,
Bob

I don't have much experience with switch-mode supplies, especially not ones
intended to generate 11kV at 1.5kW. But I have enough experience to say
this: that's a hell of a lot of energy to be mucking around with.

Even small switch-mode supplies sometimes go "bang" during development; but
when a 1.5kW supply goes "bang" it takes other things with it. And voltages
in the tens of kV encourage things to go "bang".

If I were you, I would do two things:

1. Get help from someone who really knows what they're doing (meaning at the
very *least* that they have successfully designed and built a high-power
high-voltage supply in the past), or purchase a commercially available
supply (yes, expensive).

2. Thoroughly ignore the advice of anyone (such as me) who doesn't have
credentials in this area. There are some good switch-mode supply designers
on sci.electronics.design, but I am not one of them; and in general the
Internet contains a lot more people who think they know what they're talking
about than who actually do.


Or, you could just string together a bunch of neon sign transformers, and
pray. After all, there's no reason you need a switch-mode supply; you're
just trying to generate some high voltage, right? The primary advantages of
a switching supply are that it can efficiently regulate voltage over a range
of input voltages and output loads, and that because of the high
frequencies, the transformer can be smaller and lighter. But neither of
those matter to you, as I see it. Why not just use good old 60Hz AC?
There's a bit of insight on that approach at
http://home.earthlink.net/~jimlux/hv/xfrmr1.htm.

 

[Robert Wolcott]

Walter,
Thanks for the reply. I really was hoping that the 60Hz approach would be
sufficient and I exhausted evrery possibility in that area. The problem is
that the laser needs to have a capacitor discharged through it at 20 to 40
kHz or so. I figured a resonant charging scheme would be the easiest way to
accomplish this. The primary "BANG" issue with such a supply would be the
capacitors, right? How much design work would go into a supply like this?
The University has plenty of intellectual resources, I'm not sure if they
would be up to something like this however.

Thanks,
Bob

 

[Walter Harley]

Walter,
Thanks for the reply. I really was hoping that the 60Hz approach would be
sufficient and I exhausted evrery possibility in that area. The problem
is that the laser needs to have a capacitor discharged through it at 20 to
40 kHz or so. I figured a resonant charging scheme would be the easiest
way to accomplish this. The primary "BANG" issue with such a supply would
be the capacitors, right? How much design work would go into a supply
like this? The University has plenty of intellectual resources, I'm not
sure if they would be up to something like this however.

I see you did post your question on sci.electronics.design, where you're
more likely to attract people qualified to answer it. If you don't get an
informative response, try posting again in a little while, with a title like
"Need help designing 11kV 1.5kW supply". I know there are people there who
can do and have done this, it's just a question of getting them to stop
thinking about politics and religion for long enough.

I am not qualified to answer your question. I'm just blathering on because
it's a fun thing to think about.

IMO, once you're into the kW range, asking which component is likely to go
"bang" is like asking which part of a hand grenade does the exploding.
Based on various experiences of blowing things up, I figger a 1.5kW supply
stores about the same amount of energy as a big firecracker: not enough to
penetrate a wall or substantially deform a strong steel chassis, but enough
to send shrapnel across the room and splatter bits of molten metal at high
speed. Not likely to kill you, but certainly enough to destroy your whole
project and possibly send you to the emergency room. (Wear eye protection.)

You can do the math yourself: 1 watt-second = 1 joule. There's a nice page
at http://home.earthlink.net/~jimlux/energies.htm giving real-world
equivalents for various energy levels. I'm not sure how much energy is
*stored* in a SMPS capable of providing 1.5kW; but for a linear supply it
would have to be at least enough to hold you between half-cycles without too
much ripple. If the supply completely sagged between half-cycles that would
be 1.5kW for 80msec, or about 120J; so let's imagine (SWAG alert!!) that
there's actually closer to ten times that being stored, so that there's not
too much sag. Each inductor and capacitor stores energy, of course,
although the system doesn't release all its energy during a failure.

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

I see you did post your question on sci.electronics.design, where you're
more likely to attract people qualified to answer it. If you don't get an
informative response, try posting again in a little while, with a title like
"Need help designing 11kV 1.5kW supply". I know there are people there who
can do and have done this, it's just a question of getting them to stop
thinking about politics and religion for long enough.

Yeah, ain't that a shame? One big reason I don't frequent that ng
anymore.

[snip]