Re: [CAD_CAM_EDM_DRO] Toroidal transformer ratings?? What after being rectified?

R Rogers wrote:

>Thanks to all who responded. Now, what happens to this amperage rating after it goes through a rectifier? I know the DC voltage will increase by a factor of 1.416 due to the RMS. Does the amperage stay the same or decrease due to the increased voltage?
>
>

This gets REALLY messy, fast. The problem is the rectifier is a
non-linear component,
and in this application the transformer is required to deliver short
pulses of high
current as it recharges the capacitor bank only at the voltage peak of
the sine wave.
There are some rough rules of thumb, but they depend strongly on transformer
leakage inductance and the ratio of capacitor size to current draw (or
the DC ripple
is another way of expressing it). Power supplies with very low ripple
are the worst,
because the cap is charged for the shortest duration. I've seen numbers
varying
from roughly 50% to 75% of the pure resistive rating for capacitor input
filters.
Sometimes adding a small series resistance (in this case a fraction of
an ohm)
somewhere between the transformer and cap can reduce the current peaks
without
seriously affecting regulation.

Jon