Why Does A Stepper Motors Need A Driver?

Stepper motors are not unfamiliar to most of you, but if you are not professional about the stepper motor, you may wonder why a stepper motor needs a driver, and why the stepper motor can not be directly connected to the power supply like usual motor. To help you remove your doubts, ACT Motor here explains the working principle of stepper motor driver.

Stepper motor and stepper motor driver constitute the stepper motor drive system, whose performance depends not only on the performance of the stepper motor itself, but also on the pros and cons of the stepper motor driver. Therefore, research on stepper motor driver is almost synchronized with the research on stepper motor.

There are three basic drive modes for the stepper motor driver according to the control accuracy of the motor coil current (i.e., excitation mode): full-step drive, half-step drive, and micro-step drive.

Full-step drive
During the full-step operation, the same stepper motor can be equipped with either a full/half-step driver or a micro-step driver, but the operating effect is different. The stepper motor driver energizes the two coils of the two-phase stepper motor in a pulse/direction command (i.e., the coils are charged with a set current). Each pulse of this drive will move the motor by a basic step angle of 1.80 degree (a standard two-phase motor has a total of 200 step angles in one revolution).

Half-step drive
In single-phase excitation, the motor spindle stops at the full-step position. After the driver receives the next pulse and gives two excitations at the same time, the motor spindle will move half a step angle and stop in the middle of the two adjacent full-step positions. All of the full/half-step drivers supplied by ACT Motor can perform full-step and half-step drives. Compared with the full-step mode, the half-step mode has the advantages of doubling the precision and providing less vibration at low-speed operation. Therefore, according to stepper motor drive manufacturers, the half-step mode is generally used when the full/half-step drive is actually used.

Micro-step drive
The micro-step drive mode has two major advantages: very low vibration at low speeds and high positioning accuracy. For stepping applications that sometimes require low-speed operation (i.e., the motor spindle sometimes operates below 60 rpm) or require positioning accuracy of less than 0.90 degree, micro-step stepper motor drivers are widely used. The basic principle is to perform precision current control on the two coils of the motor in sine and cosine steps, so that the distance of one step angle is divided into several micro steps to complete.


Post time: Aug-02-2022