Tom wrote: > >>> >>> >> Hello Tom, >> Doing the test I forget to ground the new motor and there was some kind >> of problem, that when I measured the tension between the PC ground and >> the machinery ground I detected 5v to 35v. >> ... >> Arnold >> > > > Arnold, > > Thanks, that is understandable. > I have an 80,000rpm Excellon pcb drill spindle that I am setting up to use in > a > small jewelry engraver. I didn't ground the spindle housing to the vfd for a > test run, and I got quite a shock when I put one hand on the spindle and the > underside of my arm on the vfd. Yeow! And this was while it was coasting after > shutting it down. It felt like 100+ volts. > Oh oh! First, you'd better check for a short to ground from one of the line wires. If not, then you need to figure out where the voltage was coming from. I'd generally expect an Excellon motor to de-excite the rotor very quickly when switched to open-circuit. I guess when the VFD is still decelerating the motor, it keeps the rotor magnetized, though. You should also know the VFD is not isolated from the mains, and runs on 340 V DC, so you should always treat anything connected to the VFD with great respect, even when it is "stopped".
The Excellon drive may have had one motor pole grounded, and that may be tied to frame ground. Certainly not a great scheme, but they all seem to use 3-wire cables. I know my motor is completely floating, but that doesn't necessarily apply to any other unit. Jon ------------------------------------------------------------------------------ Check out the new SourceForge.net Marketplace. It is the best place to buy or sell services for just about anything Open Source. http://p.sf.net/sfu/Xq1LFB _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
