Re: 3-phase variable reluctance motors

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Thomas Fritz <tomfritz@d...>
wrote:

> I've got my little grubby hands on a few of these, and I was

wondering

> what they might be used for.
>
> The rundown:
> Superior Electric Slo-Syn stepper/synchronous motor
> 65 oz-in holding torque
> 24 step/rev
> 36V operation, 2.5A
>
> These things have 4 wires...one is common, the other 3 go to the

coils.

>
> What gets me is that the shaft is so free-spinning, not at all like

the

> steppers I'm used to.

I have done a lot of work with variable reluctance / switched
reluctance motors.

In a nutshell they have only a stack of metal laminations for the
rotor. The magnetic field of the rotor will pull the pole of
lamination like a electromagnet picking up nails (Remember doing that
as a kid?). Because there is no magnets in the rotor there is no
clogging torque.

Here is the kicker. These motors are very unstable if you look at
them mathamatically. That is there strengh and weakness. The
strengh is because they are so unstable they can be ran a wide speed
range, from couple for RPMs to 15K RPM with an amazing ramp speed.
The weakness is you need a bit of processing power to control the
commutations. I have used a DSP with success. You can run them with
a stepper driver but you will have alot of torque ripple.

Dex