On Sunday 30 June 2019 06:18:24 Roland Jollivet wrote: > A while back there was some discussion on using an induction motor as > a servo motor. I can't find the thread.. > > Yesterday, at the scrapyard I hauled two of these exact motors off a > roller press; > http://www.lithronix.com/komori/komorimatic-water-fountain-roller-actu >s-power-motor-rebuilt-ni20-200fg-x4kt > > I was quite disappointed to find out there was no permanent magnets in > them, and there were no matching drives. > So they are induction, but perhaps made differently to your general > induction motor. > It's a beast of a motor for 200W... At least they come with a 1000 > P/R encoder > Since the link doesn't say how many wires go into the motor, if its 2 or 3 phase etc, its hard to make good guesses.
If its a 3 wire motor, a small 250 volt input vfd would be a good driver, and I would couple the encoder up to feed back to the vfd, such that you'd have a position servo. You would need to program the vfd to not shut down at the lower frequencies, and to not deliver more than the 1.3 amps per winding even when the vfd thinks its detecting a locked rotor. The encoder, for a position servo would need to be something that could be converted to ABX because you'd need to record the home position as x counts from the index. And I'd gate the z signal thru the home switch. Home by driving to the home sw closure, then track the counts to the z signal running in the same direction and call that home. If its a 4 wire motor, by verifying each pair of wires that has continuity is not connected to the other pair, its going to be something you may be able to drive with a microstepping stepper driver by actually useing the count diff to drive the stepper driver to brig it back into balance. There will be a residual error because it will take some error to develop the speed and direction to run the stepper driver at just high enough speed to hold motor/encoder position. The voltage however isn't going to be compatible with small drivers. And designing a high voltage stepper driver from scratch might take time. But it could be tested on the workbench table with a tb-6560 driver and a 24 volt supply. Use a PID module and turn up the PGain should give you a starting point. You should be able to reach full torque but at limited speed. Just don't expect the stepper driver to actually stop at the balance point because it will need to run slowly to maintain the balance, from this residual error. This then is the holding torque at rest. PGain way up will serve to reduce the error. In axis, one could use a circle "dial", rotating from the step signal by feeding the dial with a synthesized magnet field derived from a by $microstep as the MOD funtion, feeding the result to the dial in pyvcp, so you would see the magnetic slippage rate on screen even when it was stopped. Twouldn't need huge dials to visualize that either. Dime sized would suffice I'd think. How smooth it would be is up to the screen update rate and microstep size. This is something I've not personally tried, but if the error signal is high enough resolution, PGains can be very high. The PID running the DC spindle in my G0704 is still marginally stable at 40! So I run it at 20. And I can't hear how hard its working in the speed related noises until the servo's current setting kicks in making a squeek, and thats at 17 amps to the motor. The actual scale is switched by the back gear knob, so I have extremely solid speed control in both gears from a 1000 line encoder on the motor shaft, which in low gear makes the scale a bit above 14300. My index still comes from the spindle, so I can rigid tap in either gear. And playing on the worktable would protect things from runaway PID settings. If it shows promise then higher voltage stepper drivers and supplies can be sought or built. I'd be curious enough to try it if I had a 2 phase induction motor. But them is scarce like false teeth for hens these days. Today, and for 50 years now, multiphase has meant 3. The closest I have would be the 3/4 horse single phase with its starter winding that I took off the Sheldon. That motor runs nice & quiet, and is for sale but freight would be a killer as its huge. Frame 182 I think. > Roland > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
