Construction of Hybrid Stepper Motor

The stator of this stepper motor is same as its permanent magnet or reluctance type counterpart. The stator coils are wound on alternate poles. In this, the coils of different phases are wound on each pole, usually two coils at a pole which is referred as a bifilar connection.

The rotor consists of a permanent magnet which is magnetized in axial direction to create a pair of magnetic poles (N and S poles).  Each pole is covered with uniformly spaced teeth. The teeth are made up of soft steel and two section, of which on each pole are misaligned each other by a half-tooth pitch.

Working of Hybrid Stepper Motor:

This motor works similar to that of permanent magnet stepper motor. The figure above shows 2-phase, 4-pole, 6-tooth rotor hybrid stepper motor. When the phase A-A’ is excited with a DC supply, keeping B-B’ unexcited, the rotor aligns such that the south pole of the rotor faces north pole of the stator while north pole of rotor faces south pole of the stator.

Now, if the phase B-B’ is excited, keeping A-A’ switched off in such a way that upper pole becomes north and lower becomes south, then the rotor will align to a new position by moving through counterclockwise direction. If the phase B-B’ is oppositely excited such that the upper pole becomes south and lower becomes north, then the rotor will turn clockwise direction.

By a proper sequence of pulses to the stator, the motor will turn in desired direction. For every excitation, rotor will get locked into new position, and even if excitation is removed motor still maintains its locked condition due to the permanent magnet excitation. The step angle of this 2-phase, 4-pole, 6-tooth rotor motor is given as 360/ (2 × 6) = 30 degrees. In practice, hybrid motors are constructed with more number of rotor poles in order to get high angular resolution.

 What is a Stepper Motor Used for?

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