On 12/10/2015 4:06 AM, Gene Heskett wrote: > On Wednesday 09 December 2015 23:30:15 Todd Zuercher wrote: > >> Is there a way to issue a stop/start command to the sserial interface >> on the 5i25? >> >> I am a little bit at a loss where to begin with looking for the source >> of the possible noise issue. Peter mentioned earlier some things to >> check. The DB25 cable is the one that came with the Mesa plug and go >> kit, and is not routed near any power cables, The power source for >> the servo drives is 220 3 phase and the PC is on 110 single phase, >> arranging for them to use the same power source may be difficult. > Todd, if the power company didn't use a wild leg (and I haven't seen one > of those since back in the '50's of the last century) for the "220" 3 > phase, but a true 3 phase circuit using a transformer per phase at the > service pole, which today on this side of the pond is 254 volts per > phase, measured from phase to phase. The trick is to treat the "220" > load as a delta load, where the 4th wire neutral is just for equipment > grounding. But, measuring that same set of 3 wires from each wire to > the neutral, looking at it as a "wye" load should show nominally 127 > volts to neutral for all 3 wires. The critical measurement, to detect > whether the power company used a wild leg, is to measure from each of > those 3 hot wires, to a local ground rod. If one wire is way off the 127 > reading, they've used a wild leg, which only needs 2 transformers on the > service pole. > > If you get that 127, then just hook the PC to that and the neutral. Any > one of the hot wires will do. > > If you get an obviously higher reading on one wire, like above 140 volts, > don't hook the PC power to that one, but I would also rattle the power > companies cage asking for a true 3 phase circuit. > > Cheers, Gene Heskett
I worked with another company who installed a machine in the sticks of Alabama just two years ago and they had 3 phase power supplied to a plant that way. The installer was outside studying the transformer setup on the pole when he called me and said there were only two transformers and was asking how could that ever work. He muttered something about the plant saying that they had a "wild leg" and I had to look it up on the internet. I had never heard of it before then. But it is still around. The machine had a 30 hp motor on it running a hydraulic power unit and it was shipped wired for 480 3 phase, so the installer had to make a few changes to the machine also. The rural electric power company people came out to explain how it would work to the installer. The installer was afraid to start up the machine since he was afraid everything would burn up with the "wild leg". :-) The term "wild leg" doesn't exactly inspire confidence. Years later and it is still running. https://en.wikipedia.org/wiki/High-leg_delta Dave ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
