Does bipolar wiring of a unipolar motor create more torque if you microstep?

[christ371]

Hopefully we can keep this simple. I know that’s a tough thing to do with stepper motors and drivers.

I am trying to determine the best way to wire these e little unipolar motors for maximum low speed torque. http://catalog.orientalmotor.com/ite...ilter=&by=prod

The recommended amperage is shown at 1.4A/phase for bipolar. That’s 70% of the plate rating.

In reading the paragraph below (from the xylotx website), wiring this motor for bipolar and micro stepping doesn’t sound like a good idea.

Given what this article tells me is there any reason to wire this motor as bipolar.

Chris






6-wire motors can be wired two ways to work with the bipolar drive.
The first is half-winding. In this method, one end wire, and the center-tap wire of the phase is
used. The other end is insulated and left unused. This method uses unipolar nameplate current
specifications, and will produce nameplate torque.
The second is series winding. In this configuration, the center-tap is insulated, and unused.
This method uses all of the wiring per phase, but has double the number of wire turns as halfwinding
or unipolar mode. Because of this, the amperage requirement becomes half the
nameplate rating. (((Because the wire in the coil can handle more current than ‘half’, motor
manufacturers will often “boost” the torque rating by specifying currents up to 71% of unipolar
rated current while running in series mode. This is fine for FULL step motor drives, but bad for
microstepping drives. Using this much current will fully magnetize the motor, and destroys any
microstepping smoothness and accuracy. Any extra torque achieved by this method will
generally be lost to machine vibrations due to loss of microstepping smoothness.)))
The advantage of using series winding is that lower power drives may be used. For example a
unipolar motor rated for 4.0A/phase is over the 2.5A/phase maximum of the XS3525/8S-4.
Running in series requires only 2.0A/phase to achieve the same torque. The disadvantage of this
method is that it raises motor inductance, which in turn, slows motor coil charging time. Since
proper torque is reached only when the coil has charged to the required level, the longer it takes
to charge, the longer until full torque is achieved. This leads to slower full torque stepping rates.
Conversely, a half-winding configuration requires full nameplate rated current, but if the drive is
capable of this, the advantage is that rated torque can be achieved twice as fast as series
winding (using the same voltage, when comparing half-winding and series).