The Basic Introduction of Stepper Motor

Profile:

The stepper motor is also called a pulse motor. It is an execution motor that converts the electric signal pulse into angular displacement or linear displacement. It also is used as execution equipment in the open-loop control system.

In recent years, with the development of computer application technology, the stepper motor is used as a portion of the digital control system. In the case of non-overload, the speed, the stop position is determined by the frequency and the number of signal pulse and not influenced by the change of load.

Adding a signal pulse, the motor will rotate a stepper angle. The existence of linear relationships and the feature of only periodic errors and no accumulative errors make it widely used in speed, position and other control fields.

The Construction of Motor:

A stepper motor consists of two parts: a stator and a rotor. They are made of magnetic materials. In respect, they all have six and four magnetic poles. There exist control windings on the six magnetic poles of the stator.

The Type of Stepper Motor:

According to the excitation method, it can be divided into three categories:

(1) Reaction type(VR): The stator is made of soft magnetic material, without windings, the stator and rotor have small teeth and steps.

(2) Permanent magnet(PM): The rotor is permanent magnet material, the number of the pole of the rotor = the number of stator poles per phase, without small teeth, the step angle and torque are large.

(3)Hybrid(HB): The rotor is made up of permanent magnetic, two segments, with small teeth.

Advantage of Stepper Motor:

1, No accumulated error: Generally, the accuracy of the stepper motor is three to five percent of the actual step angle, and it doesn’t accumulate.

2, When it is working, the pulse signal in turn in a certain order is applied to the windings of each phase. (the way that the winding is turned on or off by the ring distributor in the driver)

5, the highest temperature in the appearance of stepper motor:

If the temperature is too high, the magnetic material will be demagnetized and then the torque will drop even step out. So the highest temperature in the appearance of the motor is determined by demagnetization points of magnetic materials. In common, the demagnetization points are beyond 130 degrees Celsius, and some are 200 degrees or over. So for stepping motor,  the 80-90 degrees is normal.

6, When the rpm increases, the torque will decrease: when the stepper motor rotates, the windings of each phase will form a reverse electromotive force. The higher the frequency, the greater the reverse electromotive force. Under its effect, the increase of frequency(or speed) will decrease the phase current and results in the decrease of torque.

7, The stepper motor can operate normally at low speed, but it can not be started and is accompanied by howling if the frequency is higher than a certain frequency.

Without subdivision, the stepper motor rotates for 200 pulses per revolution. If the revolution of the stepper motor is too high, stalling will occur. Although in the condition of no-load, it can reach out 1000 revolution per minute, yet it is nonsense.

Note:

1, Without subdivision, the stepper motor rotates for 200 pulses per revolution. If the revolution of the stepper motor is too high, stalling will occur. Although in the condition of no-load, it can reach out 1000 revolution per minute, yet it is nonsense.

2, The stepper motor has a good performance at low numbers. Generally, the working condition is 300-600 revolutions per minute.

3, Formula:

The number of revolutions=frequency/200*M(M is the number of subdivisions )

At experiment, it can be done up to 3000rpm