Stepper Motor Explained

The stepper motor is an open-loop control motor that converts an electrical pulse signal into angular displacement or linear displacement.

Stepper Motor

It is the main actuator in modern digital program control systems and is widely used.

In the case of non-overload, the speed and stop position of the motor depend only on the frequency of the pulse signal and the number of pulses, and are not affected by the load change.

When the stepper driver receives a pulse signal, it drives the stepper motor to rotate a fixed angle in the set direction, called the “step angle”.

Its rotation is run step by step at a fixed angle.

The angular displacement can be controlled by controlling the number of pulses to achieve accurate positioning;

At the same time, the speed and acceleration of the motor rotation can be controlled by controlling the pulse frequency to achieve the purpose of speed regulation.

The stepper motor is an induction motor.

Its working principle is to use electronic circuits to supply power when the DC power is changed into components, and the multi-phase timing controls the current.

This current is used to power the stepper motor, and the stepper motor can work normally.

The driver is the time-division power supply for the stepper motor, multi-phase timing controller.

Although stepper motors have been widely used, stepper motors cannot be used conventionally like ordinary DC motors and AC motors.

It must be composed of dual ring pulse signal, power drive circuit, etc. to form control system.

Therefore, the use of stepper motors is not an easy task.

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It involves many professional knowledge such as machinery, motors, electronics and computers.

As an actuator, stepper motor is one of the key products of mechatronics and is widely used in various automation control systems.

With the development of microelectronics and computer technology, the demand for stepper motors is increasing day by day, and it has applications in various national economic fields.

Main classification

Stepper motors can be divided into their structural forms:

  • Variable Reluctance, VR
  • Permanent Magnet, PM
  • Hybrid Stepping, HS
  • Single phase stepper motor
  • Plane stepper motor

The running performance of the stepper motor is closely related to the control method.

The stepper motor control system can be divided into the following three categories according to its control mode:

Semi-closed loop control systems are generally classified in open loop or closed loop systems in practical applications.

Variable Reluctance

The stator has windings and the rotor is composed of a soft magnetic material.

The structure is simple, the cost is low, and the step angle is small, up to 1.2°.

However, the dynamic performance is poor, the efficiency is low, the heat is large, and the reliability is difficult to ensure.

Permanent Magnet

The rotor of the permanent magnet stepping motor is made of a permanent magnet material, and the number of poles of the rotor is the same as the number of poles of the stator.

Its characteristics are good dynamic performance and large output torque.

However, such motors have poor precision and a large step angle (typically 7.5 or 15).

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Hybrid Stepping

Hybrid stepper motor combines the advantages of reactive and permanent magnets.

There are multiphase windings on the stator.

Permanent magnet material is used on the rotor.

There are a number of small teeth on the rotor and stator to improve the accuracy of the step.

The utility model has the advantages of large output torque, good dynamic performance and small step angle, but the structure is complex and the cost is relatively high.

According to the winding on the stator, there are two phases, three phases and five phases series.

The most popular is the two-phase hybrid stepping motor, which accounts for more than 97% of the market.

The reason is that it is cost-effective and works well with the subdivision driver.

The basic step angle of this kind of motor is 1.8°/step.

With the half-step drive, the step angle is reduced to 0.9°.

With the subdivision driver, the step angle can be subdivided by 256 times (0.007°/microstep).

The actual control accuracy is slightly lower due to friction and manufacturing precision.

The same stepper motor can be equipped with different subdivision drivers to change the accuracy and effect.

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