On Tue, 6 Sep 2011, andy pugh wrote: > Date: Tue, 6 Sep 2011 14:34:24 +0100 > From: andy pugh <bodge...@gmail.com> > Reply-To: "Enhanced Machine Controller (EMC)" > <emc-users@lists.sourceforge.net> > To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> > Subject: [Emc-users] Servo PSU > > I have made a servo PSU. It simply rectifies mains voltage to give me 325V DC. > https://picasaweb.google.com/lh/photo/HdNJXBD5wPqDUi9E8C46HQ?feat=directlink > https://picasaweb.google.com/lh/photo/dTcU2i7GYh53xSrqjh--BQ?feat=directlink > There is a bit of extra componentry in the box to discharge the caps > on power-off and to switch in a resistor for soft start, but basically > it is just a rectifier and some caps. > > I am a bit puzzled about the status of my -V. > I guess that my 0V will be a few volts away from neutral, which is a > few volts from earth. Should there be an explicit connection between > my DC- and earth, machine 0V, mains neutral, none of the above? > > I think perhaps I should have a 1:1 transformer to float the DC, which > would then allow such a connection.
If its direct line operated you cannot ground the V- or you will have fair explosion as you lose your rectifier. This is one disadvantage of direct line operated power supplies (both sides are "hot") If you wish to convince yourself that grounding the V- on a line operated supply is not a good idea, first measure the V- relative to ground... The other way of looking at this is to notice that you short out one of the bridge rectifier diodes if you common anything from the AC side to the DC side with one diode shorted you now have a another diode directly across the line... With our split 220V supplies in the USA a direct 220 line operated supply ends up having ~ +160 and -160 VDC output relative to neutral ( which is close to ground) > > -- > atp > "Torque wrenches are for the obedience of fools and the guidance of wise men" > > ------------------------------------------------------------------------------ > Special Offer -- Download ArcSight Logger for FREE! > Finally, a world-class log management solution at an even better > price-free! And you'll get a free "Love Thy Logs" t-shirt when you > download Logger. Secure your free ArcSight Logger TODAY! > http://p.sf.net/sfu/arcsisghtdev2dev > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------------ Special Offer -- Download ArcSight Logger for FREE! Finally, a world-class log management solution at an even better price-free! And you'll get a free "Love Thy Logs" t-shirt when you download Logger. Secure your free ArcSight Logger TODAY! http://p.sf.net/sfu/arcsisghtdev2dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
