The Introduction of Two-phase Hybrid Stepper Motor

The Definition:

The Reason why the stepper motor is suitable for the single-chip microcomputer control is that it use the digital control to control the operation of the motor. When the control unit sends a signal pulse, the stepper motor will rotate a corresponding step angle, so the realizing of mapping of the electric signal pulse and the angular displacement.

The Structure of Two-phase Hybrid Stepper Motor:

The miniature stepper motor is a two-phase hybrid stepper motor, which has a magnetic pole on the stator. There are different polarities on the rotor, which are N pole, and S pole.

The stator windings is wound according to a certain winding method, which has 8 magnetic pole. The 4 magnetic pole spaced apart are the same phase winding, which is the phase of motor.

1, 3, 5, 7 is the A phase; 2, 4, 6, 8 is the B phase. When phase A is energized in the forward direction, magnetic pole 1 and 5 are N poles, 3, 7 are S poles. The force generated by the N and S pole of stator will make the rotor rotate. The inner space of magnetic pole of the stator and the outer space of magnetic pole of rotor are distributed with pinion. These gear numbers and pitch determine the step angle of the gear pitch. The formula of gear pitch:

Z is the gear numbers of the rotor.

To make the two ends of the stator has different polarities, one end is N pole, another end is S pole, the permanent magnet should be embedded between the iron core. Although the outer space of rotor core is distributed with the pinion, which is the same as the stator, yet the pinion of N magnetic pole and S magnetic pole have a half-pitch displacement. This design is to make stator pole pair and stator in the position of the pair of teeth. The other stator pole air and rotor pinion are in the position of largest pitch displacement.

From the structure of hybrid stepper motor, the permanent field of rotor and the armature field of stator jointly produce the output torque. While the structure of the reactive stepper motor determines that the output torque is produced by armature field of stator. So , the output of the hybrid stepper motor is larger than other stepper motors.

The Working  Principle of Hybrid Stepper Motor:

From the isometric picture of the relative position of the rotor and stator, the front view of the relative position of the rotor and stator, the centerline of and the pole of the N pole and S pole of rotor have 1/4 pitch angle. According to the principle of electromagnetism, when the certain phase of stepper motor is energized, the pair of magnetic pole of the stator will generate S pole, the other pair will generate S pole, which will produce magnetic field together with the N pole and S pole of the stator, to make the stator rotate. For the polarity of the magnetic pole of the rotor is unchanged, as long as changing the energization sequence of each phase of the stator, the polarity of the magnetic pole of the stator will be changed, so the rotor rotates in a certain rotation direction.

The Energizing Method of Two-phase Stepper Motor:

Each time the stator winding of stepper motor is energized, the rotor will rotate 1/4 pitch angle, which is also called” one step”.

As long as the stator winding is energized 4 times, it will turn a pitch angle. However, the structure of two-phase hybrid stepper motor determines that it only has two phases. Only when the forward direction and reverse direction of stator windings are energized, can it complete four energizations.

The so-called single-phase energization method is to energize only one phase at a time. Use A, A^- to represent the forward and reverse energization of phase A. Use B, B^- to denote the the forward and reverse energization of phase B.

The single-phase forward turn-on sequence of hybrid stepper motor is : A -- B -- A^- -- B^-. The single-phase reverse turn-on sequence of hybrid stepper motor is :A -- B^- --  A^- -- B.

Two-phase hybrid stepping motor can also be energized at the same time, this method is called two-phase energization method.

The energization sequence of two-phase forward rotation is: AB -- A^-B -- A^- B^- -- AB^-;

The energization sequence of two-phase reverse rotation is: AB -- AB^- -- A^- B^- -- A^-B。

The two phases are energized at the same time will obtain a greater torque than single-phase energization. Whether it is single-phase power or two-phase power, they all rotate a pitch angle through 4 beats. Take 50-tooth rotor as an example:

360°/ 50/ 4=1.8°

It can be seen that the half-step working method can improve the step accuracy.

Related Article:

The Basic Introduction of Stepper Motor

What is Closed Loop Stepper Motor?