Re: [CAD_CAM_EDM_DRO] cap question

Mike Snodgrass wrote:

> Hello, on my on-going power supply project, I am putting
> together a 25A unit. By using a rough estimate of 1000mf
> per A load, I need 25000mf. I have a 33000mf 60V cap. The output of my trans is 58V.

Oh, yes, I wanted to comment on this. If the output of the transformer reads
58 V AC, you will get 82 Volts out of a full-wave rectifier and capacitor-input
filter. That will cause a problem for your caps and the Gecko drives I think you
will be using this with.

Explanation : An AC voltmeter is calibrated to read the root-mean-square (RMS)
equivalent of the energy delivered to a resistive load. This will read the same
value as a DC voltage that produces equivalent heat in that resistor. BUT, the
actual peak voltage of a sine wave is 1.414 (Square root of 2) times the RMS
reading. The capacitor of a capacitor-input filter captures the peak voltage,
so you get a higher voltage than the AC RMS reading from the transformer.
58 x 1.414 = 82

Jon