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Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
IamSmooth wrote ...
I am hoping someone can verify some calculations. N = V*10^8/(28.6*f*a*B) I got 220*10^8 / (28.6*60*2.25in^2 * 12000) = 474 turns of wire I was going to use two, which should make my primary 237 turns. Does this sound right? I was going to use 10g wire - maybe 8 if I can get it easily.
You seem to be changing the numbers while people are reviewing them! If you are stacking two cores and winding them as one, with total core area 4.5 in^2 and design flux +/- 1.2 T, then I agree that the sine wave voltage per turn is 0.929 V RMS. And that 237 turns is proper for each 220 V winding.
AWG10 wire will eventually get pretty hot at 50 amps. But pretty hot is normal for power transformers.
Registered Member #190
Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567
I changed the area because I realized I made a mistake, which someone would have pointed out. The od is 7"; the id is 3". The window area is then 2 x 1.125". I had doubled this by mistake. I might use #8 wire.
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
By my calculation, the 3" hole would be completely filled by about 467 turns of round AWG 8 magnet wire in perfect hexagonal packing.
Time to revisit the rules of thumb for maximum kVA in a 60 Hz transformer with 18.5-lb laminated steel core.
[edit] responding to your following post, I think you got it right the first time. With 2.25 in^2 core area you need 474 turns for each 220V winding. Sinusoidal RMS voltage per turn is Bmax (T) * core area (m^2) * 266.6 (V). The last factor is 2 pi * frequency / sqrt(2).
Registered Member #190
Joined: Fri Feb 17 2006, 12:00AM
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Patrick wrote ...
220V * 50A = 11kW is that the power you expect ?
That's already the power I use for some of my experiments with an isolation transformer I currently have. I want to build one for someone as they are hard to come by at this power level. I am thinking of building a 1:2 isolation unit at 10-12kva.
So, anyone have a ballpark size I need? I figure a window area of 4x3in^2 would be close.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
IamSmooth wrote ...
Patrick wrote ...
220V * 50A = 11kW is that the power you expect ?
That's already the power I use for some of my experiments with an isolation transformer I currently have. I want to build one for someone as they are hard to come by at this power level. I am thinking of building a 1:2 isolation unit at 10-12kva.
So, anyone have a ballpark size I need? I figure a window area of 4x3in^2 would be close.
nice!
i do design many of my own transformers but there always SMPS ones, but the princibles are the same. if i have the time ill review some stuff and verify or reject your math.
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designing an isolation transformer
