Permanent magnet stepper motors are available in 2-phase and 4-phase configurations. They have relatively small torque and size, and the step angles are available in the following sizes: 5.625°/7.5°/11.25°/15°. The motor consists of two parts: a rotor and a stator. Generally, the stator is a coil and the rotor is a permanent magnet; alternatively, the stator can be a permanent magnet and the rotor can be a coil.
Structure of a permanent magnet stepper motor
The entire motor's stator and rotor are axially divided into two sections separated by a magnetic shielding sheet. The two sections are spaced apart by a step angle. Each section consists of a stator, a rotor, and an annular winding fitted onto the stator. The pole pieces on the inner circumference of each stator section are arranged in a claw-shaped, annular, symmetrical arrangement. Two sets of annular windings connected in opposite directions are wound around the outside. The annular magnets of the two stator sections are connected in the same direction and coaxially, and radially magnetized.
Working principle of permanent magnet stepper motor
Let the two reverse windings in the upper section be phases A and B, and the two reverse windings in the lower section be phases B. When phases A and B are energized, the leading pole pieces of the same segment are in opposite polarities, and the rotor is in a balanced position on the stator pole pieces. When phases A and B are switched to phases A and B, the polarities of all stator pole pieces in segment B are reversed. The rotor will move one step to the left, as shown in Figure 2(b). If the energizing state is changed further, i.e., from AB→AB→AB→AB, the rotor will rotate in steps. If the energizing sequence is changed to AB→AB→AB→AB, the motor will rotate in the opposite direction.
Applications of permanent magnet stepper motors: computer peripherals, photography systems, viewpoint assembly devices, valve control, CNC machine tools, automatic winding machines, medical equipment, electronic clocks and watches, automatic embroidery machines, office automation, and home appliance industry.
