Electronics > Beginners

1-2mH 20-30A peak inductor - how would you make that?

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not1xor1:

--- Quote from: T3sl4co1l on January 24, 2019, 10:02:00 am ---Which, on a related note, generated more than a few tales of caution: the original RCA 2N3055 was a diffused mesa process or something like that I think -- almost as slow as a germanium power transistor, fT in the 10s kHz.  Laughably useless for these sorts of things.  When Motorola offered their epitaxial version (with fT ~ 2MHz, but they can't put that on the spec sheet because 2N3055 is a JEDEC spec -- not a description of the part you've ordered!), it was capable of switching comfortably in the ultrasonic range.  Until a process change occurred, or someone in purchasing bought the wrong brand, or old stock or something, and KABOOM, product failures left and right...  Fortunately, we don't have to worry about this much today (but it does remain a good reason to avoid overly general part numbers like those).

--- End quote ---

AFAIK the old 2N30355 fT was 800kHz.
I have an old ST datasheet (1977 - it was SGS-Ates back then) listing both old mesa and new epitaxial models. The old (mesa) model is specified for a minimum fT of 0.8MHz while the new one is 2.5MHz.
BTW I still have a few pieces from the early 70's ... SGS and Fairchild...


--- Quote ---
Anyway, the phase controller -- it's still a neat design exercise, especially if you run across an occasion that really is perfectly suited to phase control, or SCRs (or TRIACs) -- these are ever-fewer, but luck favors the prepared, as they say.  But beyond a design exercise, actually building it -- if you learn better through doing, yeah, go ahead and do it. :-+

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The circuit I'm simulating is not even a phase controller. The MOSFET is always switched on around pi/3, about the same time when a simple bridge+capacitor PSU would start charging the capacitor. I change just the on time according to the output voltage and load. There is a relatively small value cap after the bridge and before the MOSFET, just to dump the energy released by the transformer secondary when it is switched off.

I do not think I'll go on with this project as I do not have a suitable core.
I might rather change the phase of the switch-on (and remove the input capacitor). That might reduce the peak current (as there would be a much lower voltage delta when the inductor is switched-on), but would affect negatively the PF, the overall efficiency and stress more the transformer....
or I might just check, before all that trouble, if I can get a reasonably low noise from a switching (pre)regulator.  :)

Doctorandus_P:
I do not understand why Jay_Diddy_B designed such a complicated inductor saturation tester.

My saturation tester will be used for about 10 minutes each month on average, so no need to re-circulate the current into the Elco's.

I just used some scrap elco's from the spare parts box and a 15ct HCPL3120 integrated gate driver from Ali instead of a bucket full of chicken fodder components.

T3sl4co1l:
You surely won't understand why I built this diode recovery tester either:



Same basic idea, though in this case it's TVS clamped rather than recycled energy.  (Schematic.)

As you can guess from the large (air cored) inductor attached, it's quite sensitive to saturation and serves nicely for that purpose as well. :)

Incidentally, I used to test saturation more frequently, but as my design knowledge has advanced, I've bothered less and less often.  I suppose, take this as inspiration that it's a quite knowable process. :)

Tim

Doctorandus_P:
That's right I do not understand.
I do understand the learning experience in designing analog electronics, building it and the satisfaction of having a self designed circuit working.

But why add a whole signal generator? :-//
Why go through the trouble of dropping a 9V supply to 5V and then pumping it up to 10V again ???
I'm happy with a gate driver chip which receives it's input from my JDS6600, and my lab power supply for whatever voltage I fancy at that moment.
Everybody his own I guess.

I can understand the use of a discrete gate driver for the adjustment of the switching speed of the MOSfet in this case.
This adjustment is also usefull for testing the MOSfet itself, and that is yet again one of the reasons that I've built my tester manhatten style.
I can easily add / remove / adjust a series resistor between the driver and gate with a dab of heated liquid metal. Pot's don't work too wel here.

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