Magamp AC source

Wire size is gonna be a problem; skin-depth (for 60 Hz in Cu) is 8.4 mm. Probably you can get away with 100mm tubing, with 10mm wall thickness. The current and its return will make a tidy, but not slender, zip cord. Repulsion between those two strands is going to be 224 tons/meter; ask W. L. Gore to double-stitch the six layers of aramid cloth for the sheathing, or there may be an unzip event.

Take a 1A AC source. Scale as required...

On a sunny day (Wed, 25 Nov 2015 13:49:09 -0800 (PST)) it happened whit3rd wrote in :

The company I worked for made something like that, many kW and a one turn secondary.

This was the second to be delivered (first in my time there). The guys were going to test it but had no load, so they used transformer iron sheets as load... I was told that in the previous test that resulted in a large amount of hot iron flying through the test room, this time they had it made a bit bigger, indeed the magnetic forces are huge. Now we are talking a size that you needed a ladder to climb on, also filled with that nasty stuff, whats it PCB? (not printed boards) That was also handled in a 'safe' way, I remember them emptying the drums with what was left after filing up one of those huge things, in the river, warned me (me on top of the transformer) 'Do not touch that stuff'.

Well, :-) They made things for power stations, and accelerators too IIRC.

My next job was in a TV studio, I felt a lot safer there, more my field. Serendipity ? had it that many years later I sat on one of those big transformers at an accelerator .. again.

But, yes, magnetics, I learned a lot in those days, I was sort of disappointed companies that sell electronic parts no longer sell potcores and transformer cores (talking about conrad.nl) here. Seems modern hobbyist build everything without? IMO without being able to calculate and wind your own transformers you are only 50% in this field of electonix. Winfield left out soldering wit iron in his book IIUIC how about magnetics?

Old CRT TVs were full of flybacks, deflection coils, transductors for pincushion correction ... I calculated and wound my own. Magnetics is fun (Winfield) and very interesting. The huge transductors we used were controlled by thyristors driven by the earliest transistors, or even by some voltage sensitive tubes. Those were used everywhere, from warships to refineries.

Let me know when you're done with that experiment, I'll take that wire off your hands.

P.S.

Would like to use the truck to deliver it to the scrap yard, of course. You can have it back afterwards and if it was a rental, that would be so nice of you to take care of that payment :)

Jamie

On a sunny day (Fri, 27 Nov 2015 15:33:58 -0500) it happened M Philbrook wrote in :

Your Drone crashed? :-)

In my circuit R1=100k, the transistors are BC639 and the transformer has 2x12, 16 and 2 turns on an AL=5000 core. Works like a charm, but with an additional capacitor

1.2n the waveforms are much smoother, c.a. 160kHz. Have to learn how to take a snapshot from my brand-new scope. :-)

Best regards, Piotr

Yes, if implemented as the schematic shows, the base voltage goes crazy. But with an additional 1n2 capacitor it is in the range of

0.65..-1.2V (with a 10mA resistive load) and 0.65..-2.5V (no load), so it is well within the 5V VEB specification from the BC639 datasheet. Also the frequency depends much less on the load. The idle current is ~24mA.

The transformer has 2x12 turns of the collector windings and

2 turns of the base winding. Not much to reduce.

Best regards, Piotr

That would have been better, indeed.

I've also checked an IR21531-based generator, which has a separate generator and driver stages. Works equally well. I think that even a classic CMOS Schmitt inverter-based generator would do, but I am not going to check, as I am happy with the current results.

This AC source drives two 14nF gate MOSFETs (via two opposite-phase half wave rectifiers) with 5mA gate loads/discharge circuits each (current sources based on J310 or 2k4 resistors). There is a saturable-core reactor in between, wound on a 6mm toroidal core, which saturates completely at ~1.5A.

Best regards, Piotr

legg wrote:

More or less this:

Version 4 SHEET 1 1532 680 WIRE 640 -416 640 -480 WIRE 1296 -416 1216 -416 WIRE 1296 -384 1296 -416 WIRE 1472 -384 1296 -384 WIRE 1296 -352 1296 -384 WIRE 432 -304 192 -304 WIRE 1216 -256 1216 -288 WIRE 1296 -256 1296 -272 WIRE 1296 -256 1216 -256 WIRE 1296 -224 1296 -256 WIRE 112 -208 96 -208 WIRE 192 -208 192 -304 WIRE 1472 -128 1472 -384 WIRE 432 -112 432 -304 WIRE 1296 -112 1296 -144 WIRE 1424 -112 1296 -112 WIRE 1296 -80 1296 -112 WIRE 1424 -32 1424 -112 WIRE 304 -16 304 -144 WIRE 304 -16 272 -16 WIRE 352 -16 352 -32 WIRE 352 -16 304 -16 WIRE 432 -16 432 -32 WIRE 432 -16 352 -16 WIRE 1040 0 960 0 WIRE 1136 0 1104 0 WIRE 1216 0 1136 0 WIRE 1248 0 1216 0 WIRE 672 16 576 16 WIRE 768 16 752 16 WIRE 832 16 768 16 WIRE 960 16 960 0 WIRE 1216 32 1216 0 WIRE 1296 32 1296 16 WIRE 272 48 272 -16 WIRE 432 48 432 -16 WIRE 432 48 416 48 WIRE 336 96 336 48 WIRE 400 96 336 96 WIRE 512 96 512 48 WIRE 512 96 464 96 WIRE 96 112 96 -208 WIRE 768 112 768 16 WIRE 832 112 832 96 WIRE 960 112 960 96 WIRE 1472 112 1296 112 WIRE 576 128 576 96 WIRE 272 144 272 128 WIRE 352 144 272 144 WIRE 1296 144 1296 112 WIRE 336 160 336 96 WIRE 512 160 512 96 WIRE 272 208 272 144 WIRE 432 208 432 144 WIRE 448 208 432 208 WIRE 1472 240 1472 112 WIRE 336 288 336 256 WIRE 512 288 512 256 WIRE 1296 288 1296 224 WIRE 1040 368 960 368 WIRE 1136 368 1104 368 WIRE 1248 368 1136 368 WIRE 960 384 960 368 WIRE 1296 400 1296 384 WIRE 960 480 960 464 FLAG 96 192 0 FLAG 336 288 0 FLAG 512 288 0 FLAG 576 128 0 FLAG 1296 32 0 FLAG 1472 -48 0 FLAG 832 112 0 FLAG 960 112 0 FLAG 640 -336 0 FLAG 640 -480 Vkey FLAG 1136 448 0 FLAG 1296 400 0 FLAG 1472 320 0 FLAG 960 480 0 FLAG 768 240 0 FLAG 1216 112 0 FLAG 1424 32 0 SYMBOL voltage 96 96 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value 12 SYMBOL ind 416 -128 R0 SYMATTR InstName L1 SYMATTR Value 10m SYMBOL ind2 320 64 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L2

SYMATTR Type ind SYMBOL ind2 416 64 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L3

SYMATTR Type ind SYMBOL npn 272 160 R0 SYMATTR InstName Q1 SYMATTR Value BC547B SYMBOL npn 448 160 R0 SYMATTR InstName Q2 SYMATTR Value BC547B SYMBOL ind2 448 160 M270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L4

SYMATTR Type ind SYMBOL res 256 32 R0 SYMATTR InstName R1 SYMATTR Value 100k SYMBOL ind2 592 112 R180 WINDOW 0 36 80 Left 2 WINDOW 3 -64 8 Left 2 SYMATTR InstName L5

SYMATTR Type ind SYMBOL cap 464 80 R90 WINDOW 0 59 10 VBottom 2 WINDOW 3 19 -29 VTop 2 SYMATTR InstName C1 SYMATTR Value 1n SYMBOL res 1120 -16 R0 SYMATTR InstName R2 SYMATTR Value 2k SYMBOL schottky 1040 16 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D1 SYMATTR Value BAT54 SYMATTR Description Diode SYMATTR Type diode SYMBOL njf 304 -208 R0 SYMATTR InstName J1 SYMATTR Value U309 SYMBOL res 336 -128 R0 SYMATTR InstName R3 SYMATTR Value 5 SYMBOL res 208 -224 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R4 SYMATTR Value 1m SYMBOL nmos 1248 -80 R0 SYMATTR InstName M1 SYMATTR Value IRFP2907 SYMBOL res 1280 -240 R0 SYMATTR InstName R5 SYMATTR Value 1 SYMBOL voltage 1472 -144 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V2 SYMATTR Value 10 SYMBOL ind2 816 0 R0 SYMATTR InstName L6

SYMATTR Type ind SYMBOL ind2 976 0 M0 WINDOW 3 44 109 Left 2 SYMATTR InstName L7

SYMATTR Type ind SYMBOL res 768 0 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R6 SYMATTR Value R=1+abs(V(Vkey))*5k SYMBOL voltage 640 -432 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V3 SYMATTR Value PULSE(0 1 0 0 0 5e-4 10e-4) SYMBOL res 1120 352 R0 SYMATTR InstName R7 SYMATTR Value 2k SYMBOL schottky 1040 384 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D2 SYMATTR Value BAT54 SYMATTR Description Diode SYMATTR Type diode SYMBOL nmos 1248 288 R0 SYMATTR InstName M2 SYMATTR Value IRFP2907 SYMBOL res 1280 128 R0 SYMATTR InstName R8 SYMATTR Value 1 SYMBOL voltage 1472 224 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V4 SYMATTR Value 10 SYMBOL ind2 976 480 R180 WINDOW 0 36 80 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName L8

SYMATTR Type ind SYMBOL zener 752 112 R0 SYMATTR InstName D3 SYMATTR Value BZX84C15L SYMATTR Description Diode SYMATTR Type diode SYMBOL zener 784 240 R180 WINDOW 0 24 64 Left 2 WINDOW 3 24 0 Left 2 SYMATTR InstName D4 SYMATTR Value BZX84C15L SYMATTR Description Diode SYMATTR Type diode SYMBOL current 1216 32 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName I1 SYMATTR Value 5m SYMBOL ind 1280 -368 R0 SYMATTR InstName L9

SYMBOL zener 1200 -352 R0 WINDOW 0 24 -2 Left 2 WINDOW 3 24 65 Left 2 SYMATTR InstName D5 SYMATTR Value EDZV20B SYMATTR Type tvsdiode SYMBOL zener 1232 -352 R180 WINDOW 0 24 64 Left 2 WINDOW 3 24 0 Left 2 SYMATTR InstName D6 SYMATTR Value EDZV20B SYMATTR Type tvsdiode SYMBOL zener 1440 32 R180 WINDOW 0 24 64 Left 2 WINDOW 3 24 0 Left 2 SYMATTR InstName D7 SYMATTR Value EDZV20B SYMATTR Type tvsdiode TEXT 496 -24 Left 2 !K L2 L3 L4 L5 1.0 TEXT 64 312 Left 2 !.tran 0.01 TEXT 824 -48 Left 2 !K2 L6 L7 L8 1

This is quite a big inductor factory in Poland:

but they also have an on-line shop and sell stuff in small quantities to the hobbyists. They will probably have no problem in delivering to the NL, just ask them. They can also wind you an inductor/transforer of your own design, conforming to the the required norms etc.

There's a lot of ready-made inductors on the market (even in the shop above), so for the 'usual' needs one just buys them and forget about the problem. Custom winding is required only for SEPICs, magamps and high power, but none of them is a typical hobby stuff.

That's exactly the reason I started to play with magamps. :-)

Best regards, Piotr

Obviously not element 14 (which used to be Farnell) which does sell in the Netherlands, and still sells a useful range of ferrite cores, ex-stock and in small quantities.

For serious non-mass-market ferrites try

who sold me a small quantity of a rather specialised ferrite core a few years ago (when I was still living in the Netherlands) without making any difficulties at all.

--
Bill Sloman, Sydney

I guess I've ignored the influence of R1.

R1 current can flow into the base of either transistor, with the transformer's base winding only providing 'off' voltage bias. This base winding is always base-voltage-clamped on one conducting base terminal.

Mind you, it's got to start first.

Providing that the source is always applied suddenly and that the output is not overloaded in operation, it should 'go'.

RL