The most powerful popular science of brushless DC motor (collector's edition)

In a BLDC motor, the current-carrying conductors (stator) are stationary, while the permanent magnets (rotor) are in motion.

BLDC motor operation diagram

When the stator coil receives power from the power supply, it becomes an electromagnet and starts to generate a uniform magnetic field in the air gap. Although the power supply is DC, the switch still produces an AC voltage waveform with a trapezoidal shape. The rotor continues to rotate due to the interaction force between the electromagnetic stator and the permanent magnet rotor.

By switching the windings to high and low signals, the corresponding windings are excited to the north pole and south pole. The permanent magnet rotor with the south pole and north pole is aligned with the stator pole, causing the motor to rotate.

Animation of BLDC motor operation with one pair of poles and two pairs of poles

There are three configurations of brushless DC motors: single-phase, two-phase and three-phase. Among them, three-phase BLDC is the most common one.

(3) Driving method of brushless DC motor

The driving modes of brushless direct-acting motors can be divided into multiple driving modes according to different categories, and each of them has its own characteristics.

According to the driving waveform: square wave drive, this driving mode is easy to implement and easy to realize the motor position sensorless control;

Sinusoidal drive: This drive method can improve the motor operation effect and make the output torque uniform, but the implementation process is relatively complicated. At the same time, this method has two modes: SPWM and SVPWM (space vector PWM). The effect of SVPWM is better than SPWM.

(4) Advantages and limitations of brushless DC motors

advantage:

▷High output power ▷Small size and weight ▷Good heat dissipation and high efficiency ▷Wide operating speed range ▷Low electrical noise ▷High reliability and low maintenance requirements ▷High dynamic response ▷Low electromagnetic interference

limitation:

The electronic controller required to control this motor is expensive

Requires complex drive circuit

Requires an additional position sensor (not required for FOC)

(5) Application of brushless DC motor

Brushless DC motors are widely used in various application needs, such as various loads, constant loads, and positioning applications in the fields of industrial control, automobiles, aviation, automation systems, healthcare equipment, etc.

Industrial control field

In recent years, due to the large-scale research and development of brushless DC motors and the gradual maturity of technology, the distribution range of its drive system in industrial production has also expanded, and it has gradually become the mainstream of industrial motor development. Research and attempts to reduce production costs and improve operating efficiency have achieved significant benefits, and major manufacturers also provide different types of motors to meet the needs of different drive systems. At present, brushless DC motors are involved in industrial production such as textiles, metallurgy, printing, automated production lines, and CNC machine tools.

Automotive

In addition to the core engine, motors are also used in wipers, electric doors, car air conditioners, electric windows and other parts. As the automobile industry develops towards energy conservation and environmental protection, the motors used must also meet the standards of high efficiency and low energy consumption. The advantages of brushless DC motors, such as low noise, long life, no spark interference, and convenient centralized control, fully meet these requirements. As its speed regulation technology becomes more and more mature, its cost performance will become higher and higher, and its application in various aspects of automobile motor drive will become more extensive.

Medical equipment field

In foreign countries, the use of brushless DC motors has become relatively common and can be used to drive small blood pumps in artificial hearts. In China, high-speed centrifuges for high-speed surgical instruments, infrared laser modulators for thermal imagers and thermometers all use brushless DC motors.

Household appliances

"Frequency conversion" technology has become very common. As a symbol of Chinese home appliances, it has gradually occupied most of the consumer market. "DC frequency conversion" is favored by manufacturers and has gradually replaced "AC frequency conversion". This transformation is essentially the transition of the motors used in home appliances from induction motors to brushless DC motors and their controllers to achieve energy saving, environmental protection, low noise, intelligence, and high comfort. The development direction of brushless DC motors is the same as that of power electronics, sensors, control theory and other technologies. It is a product of the combination of multiple technologies, and its development depends on the innovation and progress of each related technology.

Office computer peripherals, electronic digital consumer products

For example, in our daily life, common printers, fax machines, copiers, hard disk drives, floppy disk drives, movie cameras, etc., there are brushless DC motors in the drive control of their main shafts and auxiliary movements.

03Differences between brushless DC motor and brushed DC motor

Comparison between Brushless DC Motor and Brushed DC Motor

Differences in working principles:

The brushed motor uses mechanical commutation, the magnetic poles are stationary, and the coils rotate. The main structure of the brushed motor is stator + rotor + brush, which obtains torque through the rotating magnetic field and outputs kinetic energy. The brushes are in constant contact and friction with the commutator, which plays a role in conducting electricity and commutating phases during rotation.

Brushless motors use electronic commutation, the coils do not move, and the magnetic poles rotate. The brushless DC motor consists of a motor body and a driver, and is a typical mechatronic product. The brushless motor uses Hall elements to sense the position of the permanent magnet poles. Based on this perception, the electronic circuit is used to switch the direction of the current in the coil in a timely manner to ensure that the magnetic force in the correct direction is generated to drive the motor.

Performance difference:

Brushed DC motor technology is more mature, with faster starting response speed, greater starting torque, smoother operation and higher control accuracy. Brushed DC motors have a simple structure and are easy to produce and process. They have been widely used in the 19th century and their technology is relatively mature. Brushless DC motors have only been put into commercial operation in the past decade or so, and their technology is relatively immature. Brushed DC motors have fast starting response speed, large starting torque, and smooth speed change, while brushless motors have large starting resistance (inductive reactance) and relatively small starting torque. Brushed DC motors have greater output power and higher control accuracy. The control accuracy can reach 0.01 mm, which can almost stop moving parts anywhere you want. All precision machine tools use DC motor control accuracy.

Brushless DC motors have lower interference, lower noise, longer life, and lower maintenance costs. Compared with brushed DC motors, brushless DC motors have removed the brushes. The most direct change is that there are no sparks generated when the brushed motor is running, which greatly reduces the interference of sparks on remote control radio equipment. Brushless motors have no brushes, and the friction is greatly reduced during operation, running smoothly and with much lower noise. This advantage is a huge support for the stability of model operation. Without brushes, the wear of brushless motors is mainly on the bearings. From a mechanical point of view, brushless motors are almost maintenance-free motors. When necessary, only some dust removal maintenance is required.

The difference in speed regulation mode:

In fact, the control of both motors is voltage regulation, but because the brushless DC uses electronic commutation, it requires digital control to be realized, while the brushed DC is commutated by carbon brushes and can be controlled using traditional analog circuits such as thyristors, which is relatively simple.

04 Global mainstream BLDC motor manufacturers (Top 10)

Currently, the top companies in the BLDC industry include ABB, AMTEK, Nidec, Minebea Corporation, Johnson Electric, United Motion Technologies, Baldor Electronics, North American Electric, Schneider Electric, and Regal Beloit Corporation.

Source: Electronics Enthusiast ABB

With more than 130 years of technological innovation, ABB has become a global leader in electrification products, industrial automation and power grids, robotics and motion. It serves customers in utilities, industry, transportation and infrastructure around the world.

AMETEK

AMETEK is a world-class organization committed to providing solutions to its customers' most complex challenges through unique technological innovations. AMETEK Advanced Motion Solutions (AMS), a subsidiary of AMETEK headquartered in Kent, Ohio, provides DC motors, controllers/drives, fans, pumps, precision-controlled blowers and custom-engineered linear motion systems.

Nidec

Nidec Motor is a leading Japanese manufacturer of industrial motors, control equipment, home appliances and consumer products. The company has multiple production and sales bases in China, Mexico, the United States and the United Kingdom.

Minebea Group

The Minebea Group was founded in Japan in 1951. Its main businesses include bearings and other machined parts, precision small micromotors and other electronic mechanical equipment. It is Japan's first professional manufacturer of miniature and fine-diameter ball bearings, and has gradually expanded into the fields of mechanical processing and electronic equipment processing based on this.