On Wednesday, April 06, 2011 01:07:23 PM andy pugh did opine: > I have 400V servo drives, 350V motors and 240V single-phase mains power. > > Is there any reason that my servo power supplies need to be anything > more than a rectifier and caps? I will probably add a PTC and an input > fuse too. > > Would a relay/resistor to discharge the caps on power-off be usual?
Since a full wave bridge off the '240', which is, at least here in the states, actually 252 these days, will give you about 358 volts, that leaves the fact that both sides of the output will be dangerously far from ground. With care, do-able. And yes, a 1k 100 watt resistor connected to each side of the line to neutral through the NC contacts of a relay, to discharge the caps on removal of power in a reasonable time would be a huge plus. It could even be done with a small switch controlling a 4pdt relay. One of P&B's 10 amp rated ice cubes comes to mind, but I believe those stop at 3pdt due to socketing. However, having extensive experience with multiple pole relays, radio and tv transmitters are full of them, I believe that I would just use 2 dpdt relays with the coils in parallel. Far more dependable IMO, and the P&B dpdt ice cubes are plentiful and dirt cheap. -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) <http://tinyurl.com/ddg5bz> <http://www.cantrip.org/gatto.html> Be careful of reading health books, you might die of a misprint. -- Mark Twain ------------------------------------------------------------------------------ Xperia(TM) PLAY It's a major breakthrough. An authentic gaming smartphone on the nation's most reliable network. And it wants your games. http://p.sf.net/sfu/verizon-sfdev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
