Re: [CAD_CAM_EDM_DRO] Synchronous motors Vs. Stepper Motors

In a message dated 8/7/00 7:15:19 AM Pacific Standard Time,
ejayhire@... writes:

<< Synchronous motors Vs. Stepper Motors

What is the Difference? >>
E.J: I think you mean the "slo-syn" type of synchronous motors here. They
are constructed exactly like a stepper-motor, but the windings are usually of
finer wire and more turns (for higher voltage than steppers use), and they
"run on" AC ("line-voltage"), with a capacitor/resistor wired between two of
the three wires. The AC is applied to the white wire, and either of the
other two. That makes a Slo-Syn run in ONE direction. If you move that AC
line to the OTHER of those two (never touching the white one!), then, it runs
in the SECOND direction. They are "synchronous" because they turn at EXACTLY
72 RPM (on 60 Hz., or, 60 RPM on 50 Hz), actually "stepping", but very
smoothly, on the "line-frequency" pulses (which are sine-waves, not low-V. DC
square-waves, as would they be for a stepper).

A "stepper" has usually two windings, so, "four wires", if a "bipolar
stepper", or, each of those windings may be center-tapped, so, "six-wires",
if a "unipolar stepper". The latter uses only 50% of the copper at any
instant, so the former is more efficient, and smaller for a given torque.
Other efficiencies, too, having to do with stored EMF, etc.

Next question? Jan Rowland, Troll