Re: stepper motors

Ted Robbins rtr@...

I would be surprised if the inductive reactance of both the 24 volt and 120
volt steppers is the same.

(for the machinists among us - Inductive reactance can be changed by the
number of windings per phase, and the physical construction of the motor.
Getting the magnetic field to build, then getting it to collapse slows the
motor down. This reactance fights the change in current through the motor.
The current produces the magnetic field, which drives the motor.)

If the reactance is the same, though, you are on to something, because
there are a lot of surplus slo-syn synchronous motors around. I've seen
some circuits aimed at overcoming some of the reactance in steppers. They
normally provide more voltage to help the current get started, then go down
to a lower voltage to keep average current within the heat dissapation
capabilities of the motor.
----------

> From: John Grant <grantjoh@...>
> To: CAD_CAM_EDM_DRO@onelist.com
> Subject: Re: [CAD_CAM_EDM_DRO] stepper motors
> Date: Thursday, July 01, 1999 8:53 AM
>
> From: John Grant <grantjoh@...>
>
> Jon Elson wrote:
> >
> > TADGUNINC@... wrote:
> > >
> > > Hopefully you guys are still on......what is the difference

synchronous ac

> > > motor, advertisement says it can be used as a dc stepper, and a

stepper

> > > motor?
> >
> > Well, usually a typical synchronous AC motor can't be used as a

stepper.

> > But, there is a particular type, low-speed synchronous motor, as made

by

> > Superior Electric and others, that are made exactly like steppers. The
> > difference is that these are usually made with 120 Volt windings, and

therefore

> > have MASSIVE inductance, making them VERY poor steppers for motion
> > control applications.
>
> I has disassembled both types of Superior Electric motors and found very
> little to no differences. Remember, a coil wound for 24 volts DC and
> one wound for 120 volts AC are almost the same.
>
> Just unsolder the connector plate and remove it, and you will see coils
> that look identical for both types.
>
> John Grant
> >
>
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