On Sun, Apr 20, 2008 at 10:42:31PM -0700, Kirk Wallace wrote: > I got the spindle VFD working on my Shizuoka and the speed varies quite > a bit. This seems to be due to interference coming from the spindle > motor leads. The cable has no shielding but there are six wires. One for > each phase, and three more that seem to connect together at the motor > end, but not to anything else.
That sounds an awful lot like the star point of your 3-phase motor. [1] While it's usually within a few volts (or ten) of ground, _if_ supply and load are reasonably balanced, it's not_for_finger_poking_or_connecting_to_ground, I submit. (If one phase goes open, there'll then be smoke, if not before. ;-) > My guess is these are for shielding and should be connected to ground > at the controller end. Has anyone seen this before? I would like to > verify this before I ground these wires. Good plan. ;-) :)) > I could cut the motor connections apart to verify how they are > connected, but the factory did such a nice job, I hate the mess it up > if I don't need to. Thanks. You could measure resistance across two phases, and compare with resistance from one phase to the star point. (A needle poked through the insulation is an alternative to ruining the neat job, if the pinhole is insulated afterwards, in case a hand goes near, under power. If an oscilloscope shows hash or spikes on the VFD output, is there any chance that a few of those chunky clip-on ferrite block suppressors would do any good? (Some of 'em are about 2" long, with a 3/8" hole, when the two halves are clipped together over a conductor.) How long are the leads to the motor? I was looking at VFDs a year or more ago, and vaguely remember something about a matching or suppressor option being required in some cases. (Didn't buy one, so put the info in the forgettery.) [1] If the motor were delta-connected, each winding would be connected to two phases, and there'd be no star point. Erik ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
