On Sunday 30 June 2019 12:38:44 Nicklas Karlsson wrote: > > On Sunday 30 June 2019 11:31:28 Nicklas Karlsson wrote: > > > On Sun, 30 Jun 2019 10:39:27 -0400 > > > > > > Gene Heskett <ghesk...@shentel.net> wrote: > > > > 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-rol > > > > >ler- 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. > > > > ... > > > > > > Vector control is needed for fast dynamic response, it's a little > > > bit extra tricky for induction motor. > > > > > > > > > Nicklas Karlsson > > > > How so, Nicklas? I am reverseing a normal 3 phase 1 hp century > > induction motor thats probably 50 yo, fast enough to make the > > spindle belts yelp in my 11x54 Sheldon. With a 1.5 hp rated clone > > vfd. Its sequenced somewhat in my .hal file, basically by turning > > the vfd down to about 10 hz, then stopping it which puts dc on the > > windings, and when the encoder says it is slow enough, gating the > > reversal on thru and ramping it back up to speed. Makes the belts > > yelp but the vfd doesn't complain. > > Well if you take your time it is possible to run, it's a simple > algorithm and work well. Vector control is only needed then there is a > need for fast and accurate response otherwise I also use simpler > algorithm. > > > Nicklas Karlsson > I think as long as the spindle encoder is working to control the G33.1 active axis, there is not, or should not, a perceptable problem. The limitation of coarse is how badly you can abuse the motor, and the only limits I can think of would be those imposed by the possible damage to its PM magnets. The motor on the G0704 for instance is a 90 volt motor, developing 1 hp at 9.7 amps according to its nameplate. I don't seem to have hurt it any with a 126 volt supply and a current limit of about 17 amps.
That sort of overdrive abuse has 2 limits, the heating time of the excessive current, and the stronger magnetics damaging its PM field magnets. The heating time is very short at that higher current, only about .4 seconds per reversal, and so far no detectable effect on its magnets. I've been running it that way for over a year now. 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
