we can try and reverse the xfmr on paper just for kicks,
from the Sowter site it looks like an EI 21 core as per the dims,
probably a sq stack,
Mag Met has 21 EI with a 1/2 inch tongue, so sq stack means A-cm = 1.61
34 dbu is 39 volts so lets get the turns,
B = 100,000,000 x Volts-RMS/4 x 1.61 cm x 20 hz x Turns,
steel cores run at 16,000 gauss all day, and all night long, so Faraday says that
16,000 = 25,000,000 x 39 volts/1.61 cm x 20 Hz x Turns,
B max = 16,000 = 30,279,503/Turns
Turns = 30,279,503/16,000 = 1892 Turns,
seems like a lot of turns for a 600 wind but remember we have a steel core so we need those turns to make up for a lack of perm,
now we can get Henries since we know the core,
Mag Met says that for 21 EI, H = 0.2431 x 10^-8 x K1 x Turns^2 x permeability,
K1 is stacking = 0.9 for 14 mil lams laced 1 x 1,
H = 0.007831947 x Perm,
now we have to guess at the perm, because it is all over the place depending on the steel and where we run it at, do we use u-initial, u-max, u-average?
inductance varies so much with freq and level, don't let it get you down, just pick a typical number, something between 10,000 and 20,000, lets try 10,000,
H = 0.00783 x 10,000 = 78 Henries,
seems high for a 600 wind, where did we go wrong?
ahh, read the fine print, Sowter is giving us level and distortion specs at 50 Hz,
do we need to re-calculate the whole enchillada? heck no, we have linear equations,
to get specs at 20 Hz we just divide, 20 Hz / 50 Hz = 0.4,
Turns = 30,279,503/16,000 = 1892 Turns @ 20 Hz,
so Turns at 50 Hz = 1892 x 0.4 = 757 Turns
remember when we said the turns count looked high? now it looks real good for a 600.
now we can get inductance, i bet it looks more reasonable also,
uh oh, inductance formula is quadratic in turns, what do we do? re calculate?
no, too lazy, just square our 0.4 correction factor, 0.4^2 = 0.16,
78 Henries x 0.16 = 12.48, now were talkin,
so if somebody drops the xfmr during shipping, we have about 10 Henries
that will stay at 10 Henries even down to 5 hz, not so with Supermalloy,
can Sowter get 757 turns on that core? sure.
can they get twice that plus shields? we need a pri and sec, ya know,
mean length turns for 21 EI is 3 inches, so we have 757 x 3" = 189 feet of wire for the pri or sec,
what is DCR? 65 ohms? what wire will give 65 ohms at 189 feet?
just check the wire table, looks like # 35, can we get 757 turns of #35 wire on a 21 EI?
sure, can we get 1514 turns for pri and sec?
sure, #35 = 25,000 turns per sq inch, 5/16 x 13/16 widow area = 0.254 sq inch,
0.254 x 25,000 = 6,347 turns, but wait, we have copper foil shields and yellow tape and KP and Nomex in there, and some sloppy winding machines with imperfect wire, and a nylon bobbin with flanges (paper wound? we have margins), so we only get about 0.4 times as much copper as predicted, so 0.4 x 6,347 = 2,539 Turns
room to spare, that means we can use thick enamel and hi-pot the thing to 5,000 volts,
ok now as far as inductance and level, ever see a B-H curve?
take the derivative of any point on there and see how many different values you get,
this is why Fred Forsell hates transformers, that weird curve, non linear as heck.
add in a little air to the core and the curve changes,
go past 2000 Hz and you have no curve.
so we just over design a bit and open up a pack of ciggys, or pray. or both.
things could be worse, you could do so much heroin that you wake up in a morgue with a toe tag, this happened to Skip Spence of Moby grape fame,
"In fact he actually ODed once and they had him in the morgue in San Jose with a tag on his toe. All of a sudden he got up and asked for a glass of water."
Happy 4th of July to whom it may apply,