Re: [CAD_CAM_EDM_DRO] Re: Power Supply

> --- In CAD_CAM_EDM_DRO@y..., <MIKEC@W...> wrote:
> > Look on the web for toroid transformers. There are articals that
> define the
> > wire gage and # turns for various power levels and ratios. Good
> luck, Mike
> > Carpenter

You can't figure the number of turns for a secondary without knowing
the number of turns for the primary. You can't figure out a good number
of turns for the primary without knowing the magnetic characteristics
of the material (ferrite or magneto steel laminations). There is a way
to calculate the best number of primary turns based on the core
characteristics, core dimensions and voltage and power level required.

But, if you are saving the primary of the transformer and replacing the
secondary to get as different voltage, you can come up with the number
of primary turns by measurement. Apply rated voltage to the primary,
and measure the voltage produced on a temorary secondary winding
of some convenient number of turns. Let's say you want 60 V DC,
and will be using a 2 diode full-wave rectifier, and a center tapped winding.
So, you need 60 / 1.414 (converts peak to RMS) = 42 Volts RMS.
lets say you put 50 turns on the core and measured 13 Volts (RMS) on
a DVM set for AC. Now, you need 42 * 50 / 13 = 162 turns, PER HALF
of the winding. So, you'd wind 162 turns, bring out the center tap, and
wind another 162 turns.

As for wire gauge, you need to use somewhat heavier wire than you'd
use in conduit, for instance, because the heat can't escape as easily, and
there is also some eddy current loss in the windings. Usual practice is
to use the heaviest wire that will fit in the 'window', or through hole,
of the transformer. This may not apply to big toroid cores, however.
In smaller transformers, the core is selected by figuring out how many
turns will be needed, and then finding a core that has just enough window
to fit that area.

Jon