On Thu, Jan 7, 2016 at 5:14 PM, Brian Morel <brianmore...@gmail.com> wrote:
> As far as the current issue, you need to be careful using old motors with > a vfd. The insulation ratings of the older motors were not designed to > handle the voltage spikes that can occur with running motors fairly > deviated from their original hz designs. > This sounds to me like a likely culprit. The high-frequency, high-amperage switching on the output side of a VFD causes high voltage transients which, if the motor isn't rated for VFD duty, can pierce the winding insulation and cause internal arcing and carbon tracks. You may be seeing higher current simply because the windings are now shorting together in a few spots. I remember spending some time searching for a good 5 HP motor with the right insulation rating to run on a VFD -- they cost a bit more, and are harder to find. I don't now remember what the magic designation is, but a quick google search just now tells me it may have been "class H" insulation. In several subsequent years of running said motor and VFD, I've never had any issues. This looks like a pretty good overview: http://energy.gov/sites/prod/files/2014/04/f15/motor_tip_sheet14.pdf Steve ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
