Re: [CAD_CAM_EDM_DRO] Toroidal Transformer Help needed

Tim wrote:

>Anybody know how to calculate the windings and wire sizes needed to
>wind a
>toroidal transformer ?
>
>

Unless the core maker has some info, you need to find the cross-sectional
area of the core. Then, you need to find the optimum flux level in the
core.
This can be determined from curves supplied by the core maker, or determined
empirically if you have the core in hand. If you have too few turns, the
flux level in the core is driven too high, and it begins to heat up.
Once you
have the optimum turns for the primary worked out, then you can figure
the secondary turns by simple ratio. If the primary is N1 turns, and the
input voltage is V1, with V2 and N2 for the secondary, then the formula is
N2 = V2*N1/V1. As for current, there are transformer tables on what wire
size to use for what current levels. These take into account the
packing of the
wire which traps the heat. Most transformer core makers give you the
"window"
area, and there are other tables that give you the number of turns of X
gauge
wire that will fit in Y square inches. You balance the copper loss in
the primary
and secondary to get the lowest losses in both windings.

>Here are my specs for the power supply I need to build
>
>2.5 kva total output approx
>
>

2.5 KVA? So, you're retrofitting a 50-ton Cincinnatti bed mill, I
guess! If this is for a
Bridgeport-size machine, even a Series II, you are going WAY overboard
(unless this is
for powering a spindle motor.)

>120 volt DC 20 amps final output
>
>I believe I need an transformer that will put out around 83 volts AC
>before rectification ,at what amps ???
>

Well, you already give it above, 20 A.

Jon