On Mon, 2008-04-21 at 18:14 +1000, Erik Christiansen wrote: ... snip > 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 I compromise the insulation, I would wand to make it obvious, but I guess it's always good to assume that insulation might have holes. I miss-typed earlier, the three "extra" wires do not connect at the motor end. They are bundled together in the connector box, but do not Ohm out. So I have three motor wires U, V, W and three that connect to nothing. > 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.) I put one on and the speed variance went down by about half. > 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.) The leads are about 1.5m (4') long. Another thing that comes to mind is that even though the machine was originally a CNC, it had a variable speed pulley system and was not designed for use with a VFD. I suppose I should really be thinking about doing a proper shielding job. Now that I am thinking about it, the stepper leads are not shielded either. Bandit must not have thought that it would be a problem, which so far it's not. > [1] If the motor were delta-connected, each winding would be connected > to two phases, and there'd be no star point. > > Erik Thanks Erik. -- Kirk Wallace (California, USA http://www.wallacecompany.com/machine_shop/ Hardinge HNC/EMC CNC lathe, Bridgeport mill conversion, doing XY now, Zubal lathe conversion pending Craftsman AA 109 restoration Shizuoka ST-N/EMC CNC) ------------------------------------------------------------------------- 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
