The difference between DC brushless motor and stepper motor

Brushless Direct Current Motor, also known as an electronic commutation motor (ECM or EC motor) or synchronous DC motor, is a type of synchronous motor that uses a direct current (DC) power source. A brushless DC motor is essentially a permanent magnet synchronous motor that uses a DC power input and is converted into a three-phase AC power supply through an inverter, with position feedback.

There are various types of motors, and brushless DC motors are the most ideal speed regulating motors today. It combines the advantages of DC motors and AC motors, with good adjustment performance of DC motors, simple structure of AC motors, no commutation sparks, reliable operation, and easy maintenance. Therefore, it is highly popular in the market and widely used in fields such as automobiles, household appliances, and industrial equipment.

A stepper motor is an open-loop control motor that converts electrical pulse signals into angular or linear displacement, also known as a pulse motor. In the case of non overload, the speed and stopping position of the motor only depend on the frequency and number of pulses of the pulse signal, and are not affected by load changes. When the stepper driver receives a pulse signal, it can drive the stepper motor to rotate a fixed angle in the set direction, called the "step angle". The rotation of a stepper motor runs step by step at a fixed angle, and 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 speed adjustment. Stepper motors are commonly used as external devices in digital computers, as well as devices such as printers, drawing machines, and disks.

The main differences between DC brushless motors and stepper motors are as follows:
1. The speed of a DC brushless motor is higher than that of a stepper motor.
2. The driving principle of DC brushless motor synchronous motor is different. DC brushless motor is controlled by the alternating power supply provided by Hall element positioning to rotate. The stepper motor is directly driven by a single pulse voltage and does not require Hall element positioning. The rotation angle can be accurately located by controlling the number of pulses added to the motor.

3. Based on different driving principles, DC brushless motors are generally used in areas where control accuracy is not required. Stepper motors are used in areas where high precision is required for control.

DC brushless motors can be divided into the following three main uses:
Continuous load application: mainly in areas that require a certain speed but do not require high speed accuracy, such as fans, water pumps, hair dryers, etc. These applications have lower costs and are mostly open-loop control.

Variable load application: mainly for applications where the speed needs to change within a certain range, there is a higher demand for the motor speed characteristics and dynamic response time characteristics. For example, in household appliances, dryers and compressors are good examples, while in the automotive industry, oil pump control, electric controllers, engine control, and other applications have relatively higher system costs.

Positioning application: Most industrial control and automatic control applications belong to this category, where energy transfer is often completed. Therefore, there are special requirements for the dynamic response of speed and torque, as well as higher requirements for controllers. Photoelectric and some synchronization devices may be used for speed measurement. Many applications such as process control, mechanical control, and transportation control belong to this category.

The main characteristics of stepper motors include:
1. The accuracy of a typical stepper motor is 3-5% of the step angle and does not accumulate.
2. The maximum allowable temperature on the surface of the stepper motor.
If the temperature of the stepper motor is too high, it will first demagnetize the magnetic material of the motor, leading to a decrease in torque and even loss of step. Therefore, the maximum allowable temperature on the surface of the motor should depend on the demagnetization point of different magnetic materials of the motor; Generally speaking, the demagnetization point of magnetic materials is above 130 degrees Celsius, and some even reach as high as 200 degrees Celsius. Therefore, the surface temperature of stepper motors is completely normal at 80-90 degrees Celsius.

3. The torque of the stepper motor will decrease as the speed increases.
When the stepper motor rotates, the inductance of each phase winding of the motor will form a reverse electromotive force; The higher the frequency, the greater the reverse electromotive force. Under its action, the phase current of the motor decreases with the increase of frequency (or speed), resulting in a decrease in torque.