Series/Parallel Bipolar steppers

[chas]

I have asked this elsewhere on the forum
and go no response, so I will try here:

I know this question has been asked more than
a couple of times, However can someone
explain once again the difference between
series bipolar and parrallel bipolar?
Typical wiring?
Advantages of each?

Trying to finalize a couple of loose ends.
Thanks

[jfirey]

Unipolar motors are four phase motors. Typically these are 8 wire motors, comprised of pairs of wires for A/B/C/D phases. Some unipolar motors are 6 wire motors, with pairs of wires for A/B/C/D phases and two center tap wires for the windings.

Bipolar motors are two phase motors. Typically these are four wire motors, consisting of A, A- (inverted), B, and B- (inverted).

If the center taps in a six wire motor are disregarded, a four phase motor can then be wired as a two phase motor. Using the A/B/C/D phases as A/A-/B/B-.

If the motor is an eight wire motor, the wires can be used to create two windings, and the unipolar motor can then be run as a bipolar, or two phase motor.

To do this, the windings are paired. That is two windings are wired in parallel, or in series, as are the remaining two.

If the pair is wired in series, resistance is doubled and therefore this motor phase now requires less current. If the pair is wired in parallel, resistance is halved and therefore this motor phase now requires more current. Motor inductance changes as well, affecting the motor’s torque characteristics.
So how do you choose?
A few things to consider;
Bipolar parallel requires a driver that can support this 2x amperage to the windings.
Bipolar parallel will maintain higher torque levels into higher speeds when compared to series.
Bipolar series also is more prone to resonance issues. Think of these as 'dead spots' in the torque curve where the motor has less torque at a given speed. Changing the speed and load affects the resonance and can assist with resolving these issues.

Go with parallel if your driver can handle it. If not series will be fine. I run several units in series mode without issues.

I have some wiring diagrams for the Pacsci Powermax II, octagonal case motors motors posted to this site's gallery. The wiring concept is the same for all 8 wire motors. They may be useful to you.

Bipolar series wiring for pacsci

Bipolar parallel wiring for pacsci

Unipolar wiring for pacsci

The color codes and shield drains relate to the particular wire I use in the cables that I offer online. Be sure to not be misled by the color of the outputs, just 'follow the lines' to build with your own cable.

The diagrams can be used as a starting point whether you use those motors or not. Check my profile for my website link if you need cables pre-wired, or send me a note.

You might read through the links below as well;

http://www.cs.uiowa.edu/~jones/step/index.html
http://209.41.165.153/stepper/Tutorials/UniTutor.htm

Best of luck,

Jason

[chas]

Thanks Jason
Finally exactly what I needed to know.
When my motors arrive I will be ordering
your wire set when I figure out exactly
what I need.
Thanks
chas