On 02/02/2017 09:42 AM, dragon wrote: > Ed Fanta does rigid tapping on his CHNC. I don't believe that he has a > breaking resistor on the VFD even. IIRC I watched the output of the > SPINx1 and it just goes from a + voltage to a - voltage and does not > "stop" he does have a fairly high line count BEI(?) encoder on the spindle. > > Many VFDs have internal braking resistors. The braking resistor is NOT specifically limited to stopping the motor. It is used any time the bus voltage rises, as it certainly will when reversing the motor. The resistor absorbs the energy removed while the motor is being slowed. The braking resistor works great on my Bridgeport mill when doing rigid tapping. Doing it on a lathe with a big chuck would make it even more important. If the bus voltage rises too high without a braking resistor, the drive will get an over-voltage fault and go to coast mode, which will not be good for your tap or workpiece. I used a vitreous enamel power resistor for the braking resistor on the Bridgeport, and two of them on my Sheldon (manual) lathe. The braking resistors made specifically for VFDs are really expensive, must have something to do with safety certification or something. I've heard of people using stove heating elements. In fact, Haas machine tools have such an element in the cabinet!
Jon ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
