Looking to build a transient generator

Why not tell us ?

..... Phil

You know Phil, no matter how hard I try, I always end up leaving out some vital detail. Thanks for helping me out :).

I would like to pass 3.2A +/- 200mA through the inductor. I realize that as the inductor gains in size, so will its series DC resistance. Therefore, at one point I might need to adjust my series resistance to keep the branch current where I want it. This will result in a very large inductor. Digikey does not carry these :(.

Gerb

You know Phil, no matter how hard I try, I always end up leaving out some vital detail. Thanks for helping me out :).

I would like to pass 3.2A +/- 200mA through the inductor. I realize that as the inductor gains in size, so will its series DC resistance. Therefore, at one point I might need to adjust my series resistance to keep the branch current where I want it. This will result in a very large inductor. Digikey does not carry these :(.

a 3.5 amp rated inductor of say 1 Henry would weigh more than I care to lift.

..... Phil

I understand its not going to be small nor light wieght. However, I need to come up with something in close proximity to what I require. Ideas anyone?

Gerb

Yet how impressive it would look in the lab, with the jack points and all.

That depends on your view of "practical".

You're definitely into the heavy metal category here, but that doesn't mean you can't find something for enough $$$.

I'd check out power transformer companies -- Hammond and Peter W. Dahl come to mind. You may be able to get something made custom, or find a power transformer with a primary winding of around 1H.

You may also be able to start with a big-iron power transformer and rewind it for your 1H.

Were I going to do this, and if no one here coughs up something more concrete, _and_ if neither Hammond nor Dahl would make one, I'd do the following: Start with Hammond's power choke catalog to get an idea of the joules/pound of a power choke, then go shopping for surplus equipment with a transformer that big. Then figure out the henrys/turn^2 constant of the thing, and wind a core.

Note that if you go this route, you want to stay aware of gapped vs. non-gapped cores -- an iron-core inductor will tend to lose inductance as the current goes up, so the energy stored won't equal I^2/2 * (starting inductance), nor will it necessarily equal the energy put in (because of core saturation). A gapped inductor will be much more linear, and much larger.

What sort of transient voltages do you foresee? Could you get by with a HV supply and a controller, or is that cheating?

Do you really need the inductance circuit to test the DUT? If you want a more destructive pulse, how about creating the shape you want with an arbitrary waveform generator or even with your original inductor circuit, then using it to control a big amp or power supply applied to your DUT?

Best regards,

Bob Masta DAQARTA v4.50 Data AcQuisition And Real-Time Analysis

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I want to create a -400V transient (switching the inductor high side) with a time contant of approximately 10mS. I have the option of taking this to a local EMC lab that has the capability of generating this pulse. However, I might want to run a few hundred products through this test. EMC lab time is expensive. For reasons I would rather not go into, I'd like to do this "on the cheap side". Thus, building my own equipment from scratch and surplus bits.

I found two companies willing to construct inductors for me. The problem, the cheaper of the two wanted $2500USD. I currently don't have that type of budget. I assume the solution you mentioed above (High voltage supply and controller) will cost even more.

Thank you,

Gerb

I've looked into what the equipment I would need to do this would cost. It is just not feasible.

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It's just no the same if the load is non resistive, of course.

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The opinion of certain vulgar individuals notwithstanding, I still think it's worth looking into kit-bashing a transformer. For $2500 you can spend a considerable amount of time rebuilding and rewinding a surplus core and still come out ahead.

I'd look to the coils that Hammond sells purely for the purpose of getting a weight vs. energy number, then think about (a) whether I want that big of a lump of steel cluttering up my shop, and (b) where in heck I could get a core that big for cheap.

Come to think of it, why look for one great gazonga of a thing, when you can build it yourself out of smaller chokes?

Just from the Antique Radio Supply catalog, I see that you could put together 10 10H x 500mA chokes in parallel for a 1H, 5A choke. It'd weigh 210lbs less your frame, and cost you 10 x $68.45. That's a heck of a lot less than your $2500. Hammond also has a 100mH, 5A, 14lb choke (the 195T5) that you could string in series, but Antique Radio Supply doesn't list it (and if you're getting 10, you'd be better off getting it straight from Hammond anyway).

Check to make sure you're not getting a "swinging" choke, unless a swinging choke is what you want.

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Dooohhhh! Interesting...

Gerb

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Thank you. Now this is more inside my budget :).

Gerb