Re: [CAD_CAM_EDM_DRO] Strange motor - question

Jerry Kimberlin wrote:

>
> I did some more testing and now think it is probably not a 230v
> motor. I made an assumption since I've never come across a 3 phase
> motor that runs on 120, but that is probably what it is. Using a
> Variac and starting the motor by hand, It will run on 40 vac quite
> nicely, but without having the 3 phase there, begins to rattle at
> about 65 vac. Higher voltage gives more rpm too. It will do this
> on any pair of the 3 input wires showing that the motor is OK. But
> at 120 vac, it won't run on my Hitachi SJ100 which faults, since it
> only puts out 200-240 volts. I think that is understandable now.

Slightly unusual, but not extremely odd. it probably was used in some
gear that had a delta-wye transformer in it, and was used to take
standard 230 V L-L 3-phase and deliver a bunch of 120 V L-L
single phase loads inside.

> The rotor appears to be a solid block of metal. I am assuming it is
> an ordinary motor, but the rotor is only about 2" OD and has some
> aluminum ends closely fitted to the metal armature (iron or rare
> earth?) so I can't see the construction.

Yup, that sounds like a standard induction rotor. it really isn't a solid
block, VERY close to the OD it has a bunch of holes that run axially
through the rotor laminations, and insulated aluminum bars are pushed
into them. These bars are crimped or welded to aluminum discs which
often also serve as fan impellers. These bars form the shorted turns
of the induction fireld winding.

Jon