On Tuesday 28 September 2021 13:43:54 John Figie wrote: > Gene, > > So It seems like you have verified that the PSU shutdown is not caused > by a shoot through current in the H bridge and that is good. > Now if the motor is running at 24V and you instantly reverse the power > supply, the current going into the motor will not instantly reverse > direction because of the motor inductance. But if the inertia is large > compared to the inductance (large in terms of stored energy) then like > you say, the current will soon get very large as you will have > essentially 48V (24 from PSU and 24 from back EMF) across the winding, > limited only by the resistance. > > Now I am working on making some torque mode drives for my lathe > retrofit. But I would like to see if I can make a decent motor and > drive simulation using LTSpice. I already have what I think is a > reasonable motor model. I intend to share the simulation model once I > am confident in it. It can also be used to show any benefit in true > torque mode, where the current is the command input to the drive, > rather than voltage mode - what I think you have. I have found that if > a simulation can be set up and validated it gives much more insight > into a particular problem - you can make changes quickly and you can > measure things that would be otherwise very difficult. > > It would be cool if I could get more info about your motor and > mechanics. > > Like: > > No Load Speed - maybe not feasible for you since you would need to > take your machine apart.
My best estimate would still be a WAG. > Nominal voltage and speed 24 volts, 100 watt rated, but I suspect from the heat rise that would be an ICAS rating. Service target is a chain driven estate driveway gate and one open/close wouldn't be anywhere near CCS. > Stall current Since the psu is a 300 watt model and doesn't crowbar at the limited accells I can use, I'll say a WAG at 10 to 12 amps. > Stall torque unk, more than enough to turn the bs-1. Including I believe with a cutting load applied > DC resistance That I can get. > Inductance I have an esr meter that might report that, none of the several dvm's I have does inductance. > Inertia of rotor and worm - that one may be hard to find. but maybe it > can be estimated by the mass, and diameter of the armature and > connected load. The mass on the worm gear side will probably not be > significant because of the high gear ratios. > > Regards, > > John I'll get back with anything else I can measure but I've got some pill shopping to do yet today, scripts running out etc. Thanks John. > > > > > _______________________________________________ > 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, 1940) 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
