Stepper Motors: Unipolar/Bipolar Windings
Stepper Motors: Unipolar/Bipolar Windings
Stepper motor windings are produced in two winding versions: Bipolar and Unipolar configuration.
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Bipolar winding configuration (as in sections above) Current flows through whole windings, in alternating direction. JE two-winding stepper motors have 4 leadwires. |
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Switching scheme of one winding:
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Unipolar winding configuration Each winding has a center tap. The JE two-winding stepper motor has 6 leadwires or 5 leadwires, if the center taps are connected inside the motor. |
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Switching scheme of one winding:
Unipolar motors are usually applied for small motor sizes, in combination with constant voltage driver circuitry (low cost transistor arrays available for small motors).
Applicational notes for Unipolar motors:
| Driver circuitry costs | Lower costs of driver circuitry, only 2 transistors per winding |
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| Motor costs | Higher costs of motor , 6 or 5 leadwires and windings need a center tap |
| Performance | Lower holding torque TH of only 1/√2 compared to bipolar motors
(same motor size, same temperature increase). Lower torque at low and medium step frequency. For the same TH specification - higher current needed (higher energy consumption). Higher torque at high step frequency, due to lower ratio L/R and therefore faster current rise. |