Re: [CAD_CAM_EDM_DRO] Re: Power Supplies

In a message dated 4/16/2005 1:38:43 A.M. Central Daylight Time,
dshiels@... writes:

I find a transformer that outputs 75v @ 10 A add a rectifier bridge say a
400V 10 amp model and a
20,000 uF 75VDC Capacitor and a bleed resistor. Does this sound correct?


No! Remember the voltage "rating" of the transformer is AC, not DC. Once
you full-wave rectify that and add sufficient capacitor filtering, you
multiply the "ideal" AC by SQR(2) (which is about 1.414). So, your UNloaded DC
would be 106 Volts, maybe 20% more, due to various tolerances and expectable
variations. That WILL fry the Gecko (rated for 80 volts!), even with no motor
connected.

You need a LOWER voltage transformer. 45 VAC would be SAFER. Another
thing: The "Gecko White Papers" available on-line will tell you how to calculate
things re power-supplies. You do NOT need the "motor-rated amps" for a
transformer. I found this out by surprise, "at the breadboard". Mariss set me
straight. Do the math. Read the White Papers.

Jan Rowland


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