Hi,
I know that it is possible to drive a unipolar stepper motor as if it is bipolar. Clearly, for example, we can ignore center tap wires of a 6-wire unipolar stepper and drive it using a bipolar stepper driver through A+,A- and B+,B- wires.
In such a case, do we loose or gain something, in terms of, let say, step angle, torque, speed, necessary current, etc?
Thanks
AFAIK stepper motor drivers for bipolar motors are much more common.
I think (but I am by no means certain) that unipolar motors exist so much simpler drive circuits can be used.
...R
Indeed unipolars were much easier to drive before bipolar chopper drive chips were cheap and plentiful.
Unipolar steppers use more copper for the same performance level, bipolars use the windings to maximum advantage. A 6- or 8-wire motor is more efficient driven bipolar than unipolar (can provide more torque for the same amount of heat dissipation).
A 6 or 8 or 4 wire motor driven bipolar are the same thing electrically (8 wire have two different impedances available).
The modern approach to steppers is to treat them as specialized 2-phase PMAC motors driven open-loop. A typical stepper is like a PMAC with 50 pairs of poles rather than 1 or 2 pairs.
Thank you MarkT and Robin2 for your answers. But what about step angle and accuracy if I drive unipolar steppers as if they are bipolar as I mentioned above?
There won't be any loss of accuracy. And with a specialized bipolar stepper driver you have the option of micro-stepping.
...R
Many thanks:)