Andy,
looks like a neatly made power box. Rectifying AC line power without 
potential insulation, however, is unusual and bears some risks.

- Be aware that both of your DC lines will have potential to ground, 
none can be grounded.

- Be sure that every metallic enclosure that is powered by this device 
will be properly connected to protective earth (PE) and none of the 
motor's leads will be near earth!

- Be sure that the drives and motors have sufficient high voltage 
protection to ground, check technical specs.

- You can't connect the control circuitry, which will be ground 
referenced in most cases (zero of the 5 V supply connected to the metal 
parts and PE)  without an optical or other insulator which makes things 
more complicated than usual.

- Think about the effects that plugging the mains plug 180 degrees 
turned over could have, don't rely on wires having seemingly no 
potential in one case!

- Be aware of the fact that ordinary switches, relay contacts, fuses 
etc. can switch off much less DC voltage than in the AC case. A DC arc, 
several inches long, will be stationary at as little as 110 volts DC in 
some cases. And it creates a lot of heat... In the good old DC times we 
used to have spring loaded, fast acting switches with wide gaps between 
the contacts, remember?

- Honestly: You must be a much braver man than I because I myself 
wouldn't dare using that box knowing that I'm too much used to the way 
of thinking that one leg will always have zero volts.... Have you 
considered using a 1:1 transformer?

Good luck!
Peter


andy pugh schrieb:
> 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.
>
>   


------------------------------------------------------------------------------
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

Reply via email to