Re: [CAD_CAM_EDM_DRO] Re: stepper wiring and AC stepper

Thank You Mariss for the short course on AC synchronous stepper motors.

You have provided us a lot of education, as well as good products.

I did run those motors as bipolars, and they did have a lot of torque at
slow speeds. I supplied them with 90 v DC, I recall, and used Caps to give
them the full pulse quickly. I moved a big gantry with two of them driving
the same gear. I could sit on the gantry and ride it along. The gantry was
heavy, probably 100 lbs. The X axis was driven on both ends. One end rode
along a two inch TGP solid round shaft with two slotted bronze bushings, the
other on a Big roller.

I won't bore you. I know you are busy. Again, Thanks a lot.

Tom E.

----- Original Message -----
From: <mariss92705@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, April 04, 2001 11:04 AM
Subject: [CAD_CAM_EDM_DRO] Re: stepper wiring and AC stepper


> Hi,
>
> It is an excersize if futility to use an "AC synchronous step motor"
> as a bipolar step motor, though you can do it.
>
> Just like "real" step motor, it has two windings except one end of
> each winding is connected internally and the common wire is brought
> out, for a total of 3 wires.
>
> One winding ( common and one end) connects to 115VAC, driving it with
> a 60Hz sine wave. The remaining wire has a capacitor in series that
> provides a 90 degrees phase shift at 60Hz. This phase shift means
> that winding is driven with a cosine current. Direction is determined
> by which winding gets the cap.
>
> What you have then is an infinite resolution microstepper that runs
> at 240 full steps per second.
>
> The problem is it is designed to run of off 115VAC at 240 full steps
> per second. This means the motor must have enormous inductance to
> limit current at such a low speed and high voltage.
>
> This motor would require a 1,600 volt bipolar drive ( 10 times 115VAC
> times 1.41 ) to get the same torque at 2,400 full steps per second!
>
> You can open the back of the motor, identify the common connection,
> seperate it into individual wires and bring them out. What you would
> have after your efforts would be a motor that completely runs out of
> steam at 60 full steps per second using a 40VDC driver. Not exactly
> blazing performance.
>
> These motors are cheap on the surplus market because they have near
> zero value for anything other than its designed purpose; a fixed 72
> RPM motor.
>
> Mariss
>
>
>
> --- In CAD_CAM_EDM_DRO@y..., "Tom Eldredge" <harmonyt@r...> wrote:
> > Marris,
> >
> > Ya know, I think you are correct. Now, how did I hook up those AC
> > synchronous motors and drive them as biplar driven steppers?
> Maybe they
> > had three wires? I know they were AC because I used some as AC
> motors.
> > You could reverse them easily with a switch controlling the
> cap/motor hook
> > up.
> >
> > Tom Eldredge
> > ----- Original Message -----
> > From: <mariss92705@y...>
> > To: <CAD_CAM_EDM_DRO@y...>
> > Sent: Tuesday, April 03, 2001 12:04 PM
> > Subject: [CAD_CAM_EDM_DRO] Re: stepper wiring
> >
> >
> > > Hi,
> > >
> > > AC synchronous "steppers" do not have 6 wires.
> > >
> > > Mariss
>
>
>
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