Bipolar Stepper Motor

A bipolar stepper motor has separate phase windings without a center tap (no common lead). Many two-phase bipolar motors are supplied with four leads, with each phase brought out as a pair of wires.

Because the current in each phase must flow in both directions, the driver needs an H-bridge output stage (implemented as an IC or a driver module). Current reversal is what changes the magnetic polarity of each phase during stepping.

H-bridge parts can be used with small motors if their voltage, current, and thermal limits match the motor’s specifications and duty cycle. Torque depends on the winding configuration, drive current setting, and the mechanical load profile.