I intend to wind my own transformer core for a custom application. I understand that with higher power requirements and higher currents through the transformer windings means that you need a physically larger core to handle all the flux without saturation.
Assuming you had 2 or more toroidal transformer cores, could you stack them to make something that looks less like a donut and more like a sort of "tube" and wind around them all at once to make for a larger core if you can't find one the size you need to begin with?
Assuming you had 2 or more toroidal transformer cores, could you stack them to make something that looks less like a donut and more like a sort of "tube" and wind around them all at once to make for a larger core if you can't find one the size you need to begin with?
That was paralleling cores.
I use another way too, connecting flux in series to get 100KV secondary from 50Vprimary with only 1000turn secondary and 5turn primary, 10 cores connected in serial flux.
I use another way too, connecting flux in series to get 100KV secondary from 50Vprimary with only 1000turn secondary and 5turn primary, 10 cores connected in serial flux.
The problem with stacking too many cores is that the winding resistance goes up. This is because the allowed flux goes roughly as the cross-sectional area of the core, but the winding resistance goes as the length of the periphery. You get the best ratio by having a core which is roughly round/square in cross-section.
So stack two or maybe three. After that you will get diminishing returns.
So stack two or maybe three. After that you will get diminishing returns.
are you talking about stacking toroid cores?
I think the power capability of the transformer and it's core varies as the square of the core area.
If that square rule applies and you stack two identical cores, then you increase the power roughly by four times.
That would need double the thickness (4 times the area) of wire to give four times the current and four times the power with the same voltage.
But you would have to re-wind the primary for this four times capability. Are you able to wind the primary/ies safely?
I think the power capability of the transformer and it's core varies as the square of the core area.
If that square rule applies and you stack two identical cores, then you increase the power roughly by four times.
That would need double the thickness (4 times the area) of wire to give four times the current and four times the power with the same voltage.
But you would have to re-wind the primary for this four times capability. Are you able to wind the primary/ies safely?
what is your application? you can get several KW form single core, if your freq is ihgh enough. Stacking will increase that. also, depends on app. you could used more cores, wire secondary in series... really depends on what you need to do
The answer to the basic question is yes you can stack cores. Just for clarification, the power handling capablility of a transformer is directly related to the core area, not core area squared.
Are you sure?the power handling capability of a transformer is directly related to the core area, not core area squared.
xformer designer.exe gives the following
core 1square inch 31VA
core 2square inch 125VA
core 4square inch 502VA
all for mild steel 0.8T, 240Vac, 50Hz
Twice the core volume, twice the throughput capacity. The most efficient windings have a square or round cross-section, as has already been mentioned. But for higher frequencies with enough core overdesign sometimes the problem of winding loss gets pretty small.
Andrew E,
how do you calculate core volume?
The bit of core inside the turns? which in a toroid is the whole iron.
Or in an EI is the length of the wound leg times the core area?
Or is it the whole iron of an EI?
Or R core the wound lengths (the straight bits) times the core area?
how do you calculate core volume?
The bit of core inside the turns? which in a toroid is the whole iron.
Or in an EI is the length of the wound leg times the core area?
Or is it the whole iron of an EI?
Or R core the wound lengths (the straight bits) times the core area?
You calculate the mean magnetic path length through the center of the lamination.
On a toroid this is pi(OD + ID)/2
On a toroid this is pi(OD + ID)/2
does that equate to the "whole iron" volume?
A doubling of the size of a transformer core would give 4times the core area and 8times the volume.
Surely the power capability can't vary as the cube of the Sqrt(core area)?
A doubling of the size of a transformer core would give 4times the core area and 8times the volume.
Surely the power capability can't vary as the cube of the Sqrt(core area)?
http://www.diyaudio.com/forums/powe...formers-power-requirements-2.html#post2337162
to clarify "side note, power scales with flux squared, which is the biggest reason why cheap stamped E core transformers run 10-20% higher than they should, wasting 20-40% the cost to manufacture in electricity.. every year..." should read "10-20% higher flux density"
in the case of two toroids.. ymmv.. you're only saving up to 25% of the Cu that two separate transformers would use up, assuming the core is square... but most of the cores i've unwound are rectangular, 1:1.5 , so you'll save even less copper, somewhere between 20 and 10%.
you would be much better off unwrapping the second core and wrapping it around the first one.
to clarify "side note, power scales with flux squared, which is the biggest reason why cheap stamped E core transformers run 10-20% higher than they should, wasting 20-40% the cost to manufacture in electricity.. every year..." should read "10-20% higher flux density"
in the case of two toroids.. ymmv.. you're only saving up to 25% of the Cu that two separate transformers would use up, assuming the core is square... but most of the cores i've unwound are rectangular, 1:1.5 , so you'll save even less copper, somewhere between 20 and 10%.
you would be much better off unwrapping the second core and wrapping it around the first one.
Andrew-
It reads like you're stuck trying to apply the numbers to "size", when it seems clear that stacking two same toroids or doubling the lam stack height is "doubling the size of the transformer", which allows twice the power capacity at the same frequency.
power sine excitation:
P=.707JfWaB x 10e-8
J - current density Amperes sq. cm
f - frequency
W - winding window area sq. cm
a - core cross sectional area sq. cm
B - flux density Gauss
It reads like you're stuck trying to apply the numbers to "size", when it seems clear that stacking two same toroids or doubling the lam stack height is "doubling the size of the transformer", which allows twice the power capacity at the same frequency.
power sine excitation:
P=.707JfWaB x 10e-8
J - current density Amperes sq. cm
f - frequency
W - winding window area sq. cm
a - core cross sectional area sq. cm
B - flux density Gauss
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Andrew Eckhardt is correct. AndrewT I suspect that in the examples you gave the winding area (W in Eckardt's equation) also changes.
How do J & a interact?Andrew-
It reads like you're stuck trying to apply the numbers to "size", when it seems clear that stacking two same toroids or doubling the lam stack height is "doubling the size of the transformer", which allows twice the power capacity at the same frequency.
power sine excitation:
P=.707JfWaB x 10e-8
J - current density Amperes sq. cm
f - frequency
W - winding window area sq. cm
a - core cross sectional area sq. cm
B - flux density Gauss
core cross sectional area is doubled.
What happens to J, the current density?
Stacking two toroids leaves f (mains frequency), W (window area) and B (flux density) unchanged.
What, exactly, is "power sine excitation"?
I don't think so. I have downloaded the exe after you responded and no where does it ask for window area. It does ask for core cross-sectional area or VA and any 3 out of the following 4: Mains voltage, Mains frequency, Max flux density, Primary turns.I suspect that in the examples you gave the winding area (W in Eckardt's equation) also changes.
Should have maybe written "Power: sine excitation".
The equation is a straight product of factors. Current density is only how much current you pass through winding cross sectional area. However, if you double core cross sectional area, B is halved, so available power throughput is doubled.
Stacking two same cores halves B. Or for fixed B, doubles power...
The equation is a straight product of factors. Current density is only how much current you pass through winding cross sectional area. However, if you double core cross sectional area, B is halved, so available power throughput is doubled.
Stacking two same cores halves B. Or for fixed B, doubles power...
Johan link shows
note that core area has increased 4times and power has increased 16times, i.e. core squared, provided we can cool the bigger transformer.Take two identical transformers, scale one 2x in every dimension.
Core area is 4x, window area is 4x, volume of core and copper is 8x
Constant current density and same flux means 16x power
I wonder if this is where you are both going wrong?The equation is a straight product of factors. Current density is only how much current you pass through winding cross sectional area. However, if you double core cross sectional area, B is halved, so available power throughput is doubled.
..................... Or for fixed B, doubles power...
B (core flux) stays the same.
If you retain the same number of turns then to get the same flux density you need to double the current. If you double the current you need to double the wire cross sectional area (40% increase in diameter or bi-fillar wound using same diameter).
Now the ampere turns has increased by a factor of two.
What does that do to the VA capability?
The window area, current density thing can make it unnecessarily complex to think about flux density. You can also use the turns per volt arrangement to think more directly just about core saturation.
N/V= 10e-8/4.4faB
N - number of turns
V - volts
F - frequency
a - core cross sectional area
B - Gauss
N/V= 10e-8/4.4faB
N - number of turns
V - volts
F - frequency
a - core cross sectional area
B - Gauss
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