On Tuesday 27 July 2021 05:13:28 andy pugh wrote: > On Mon, 26 Jul 2021 at 23:55, Earl Weaver <[email protected]> wrote: > > I have a lathe spindle with 8 in. chuck that is run with a 5HP > > Reliance DC Motor and Reliance DC Drive. > > What kind of DC motor is this? Is it a permanent-magnet servo motor? > > Typically DC motors perform better at lower speeds than an AC > induction motor, so I don't think that swapping to a motor/VFD > combination will help. > > If the motor is running closed-loop speed control from the tachometer > then, as suggested, you should test whether full rated current is > being applied when the lathe is cutting at the limit. > > I would expect a speed-controlled loop spindle to feel springy. As you > move the chuck faster than commanded speed the drive will reduce the > current to try to slow the spindle (maybe even reversing in to > braking) > Then as you wobble it back the other way it will take some time to > wind up the other way. > > The only way to make the spindle feel "stiff" in your test would be to > close the position loop with the encoder, but then how do you drive it > as a spindle with a speed command?
With a honking big power supply, and a high resolution encoder. I have 2 machines with 1hp rated motors, both claiming to be 90 volt motors with an FLA rating of 9.7 amps. Both are powered by oversized power supply's outputing around 127 volts at nearly 20 amps. One has a very hi res encoder with a scale for 1 rev of a bit over 7000 in hi gear,and a bit over 14,000 in low gear. That one has a Pgain of 20+ in its pid. Control isn't just "stiff", the only way I know when I am hitting the limit of about 17 amps into the motor while rigid tapping, is by listening carefully for the iron in the motor to chirp whn it runs into the limit set in a pwm-servo amp that Jon Elson makes. Up to that point, the tach does NOT sag because of the load. However, the OP's motor is severely disadvantaged by the 1/1 drive if it is getting the nameplate FLA, but I'd be checking the PSU. Something is definitely fubar. The meter readings I asked for but haven't yet seen would be a huge aid at pointing the finger in the right direction. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
