RE: [CAD_CAM_EDM_DRO] Powersupply

Doug,

You've confused me with your calculation!

44Vrms * sqrt(2) = 62.25Vpeak

less a full-wave bridge @ 1.4V => 60.85V

The average DC volts will be a little less than this, depending
on load (and hence the ripple).

Mind you, I'd hesitate using a 63V rated cap for this unless the
environment is controlled and the ambient will stay at room temp.
(In a hobbyist's situation this may present no real issues).
If there's any chance that the cap's core temperature will rise
above 85 deg C (due to ambient temperature and/or self
heating due to ripple current flowing through the cap's dynamic ESR)
then its operating voltage will need to be derated.

Running an electro close to its rated voltage will reduce its
operating life, as will elevated temperature operation.
(see
http://www.illcap.com/LifeCalculator.asp
http://www.cde.com/SelectingInverterCaps.pdf
http://www.chemi-con.com/guide/pg2.php
if you're interested)

John Haddy
Sydney, Australia

> -----Original Message-----
> From: doug@... [mailto:doug@...] On Behalf
> Of Doug Fortune
> Sent: Thursday, 28 August 2003 5:20 AM
> To: cad_cam_edm_dro@yahoogroups.com
> Subject: Re: [CAD_CAM_EDM_DRO] Powersupply
>
>
> Dan wrote:
> >
> > I have some pieces that you might be interested. $60 plus shipping
> >
> > 44VCT toroidal transformer - 250va
> > (2 x 22V secondaries at 120V input)
> > 56,000uf 63v Capacitor with hold down clamp
> > Bridge Rectifier
> >
> > Combined components will result in a 60vdc 5A power supply
> >
> > http://66.12.111.114/bay/CNC/Power_Supply.jpg
> >
>
> Hi Dan:
>
> That looks like an excellent mid-range setup. However,
> once you build it with the above components, you will find
> you get exactly 65.75V (+/- .25V) which would be inappropriatly
> high for Brian's Gecko G201-driven 2.5VDC steppers and the
> specified 63V cap.
>
> best regards
> Doug Fortune
> http://www.cncKITS.com
>
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