A brushless motor is a synchronous motor that uses a DC power supply. It realizes the commutation function through an electronic commutator, without the need for carbon brushes and commutators, thus avoiding friction loss, spark interference and maintenance costs. Brushless motors have the advantages of high efficiency, high performance, low noise, low vibration, long life and high reliability, and are widely used in automobiles, industry, home appliances, aerospace, medical equipment and other fields. This article introduces the origin of brushless motors, the driving principles and characteristics of brushed motors and brushless motors, the classification and technical barriers of brushless motors, the application of brushless motors and the market size of brushless motors.
1. The Origin of Brushless Motor
The inventors of the brushless motor were German theoretical physicist Ernst Werner von Siemens and physician Angelo Fausto Dori. As early as the 1860s, German physicist Ernst Werner von Siemens began to study the working principle of the motor.
In 1886, the first practical DC motor that could run at a constant speed under variable weight was introduced. Frank Julian Sprague was its inventor, and it was this motor that provided a catalyst for the widespread use of motors in industry.
In 1949, Slovak engineer Emil Petras invented the first brushless DC motor, which used the principle of reversing AC current to achieve uninterrupted rotation. This marked the beginning of the era of brushless motors.
This practical motor adopts a brushless form, that is, an AC squirrel cage asynchronous motor, which not only eliminates sparks and voltage losses at both ends of the winding, but also can deliver power at a constant speed. However, asynchronous motors have many insurmountable defects, and motor technology has developed slowly in the past.
Shortly after the birth of brushless motors, people invented DC brushed motors. DC brushed motors became the mainstream at the time because of their simple structure, easy production and processing, convenient maintenance, and easy control.
In the 1960s, American electrical engineer Terry Lakin invented a three-phase brushless motor with strong magnetic force and high efficiency (the phase of a three-phase motor refers to the coil winding in the motor, three phases and three windings. Specifically, it includes three phases, namely phase A, phase B and phase C. The three-phase motor uses a three-phase power supply as energy and generates a rotating magnetic field through three independent coils, thereby driving the motor to rotate). This innovation broke the working principle of traditional motors and was hailed as a revolutionary breakthrough in the history of motors. Terry Lakin also became the father of brushless motors.
Since its invention, brushless motors have the characteristics of low noise, lower maintenance cost, more reliable performance, lower failure rate, better external characteristics, small no-load current, and wide speed range compared to brushed motors. Since the 1960s, countries and regions such as Europe, Japan, and South Korea have successively carried out research on brushless motors and applied them in aerospace, robotics, consumer electronics, etc. At present, China has also become one of the major countries in the production and application of brushless motors in the world.
2. Brushed Motors vs. Brushless Motors
(1) Driving principle of brushed motor
The driving principle of the brushed motor is based on the law of electromagnetic induction and the commutation mechanism of current. Its core structure includes stator poles, rotor windings and a mechanical brush-commutator system. When the DC power supply is connected, the current enters the rotor winding through the brushes and commutator, generating an electromagnetic torque, which interacts with the stator magnetic field to drive the rotor to rotate. As the rotor rotates, the commutator periodically changes the direction of the current to ensure that the rotor generates a continuous unidirectional torque and achieves stable rotation. This structural design simplifies the control system and has the advantages of large starting torque and simple control, but the mechanical friction between the brushes and the commutator causes wear and sparks, affecting life and efficiency. Brushed motors became the mainstream as soon as they came out because of their simple structure, easy production and processing, convenient maintenance, and easy control.
However, brushed motors have the following problems:
A. As wear parts, brushes produce carbon ash and other substances when working. Brushed motors need maintenance and cleaning after a period of time.
B. Due to the structure of brushed motors, the contact resistance between brushes and commutators is large, resulting in a large overall resistance of the motor, which is prone to heating and other problems. Permanent magnets are thermal elements. Excessive temperature will cause them to demagnetize, resulting in a decrease in motor performance.
C. Due to resistance problems, a considerable part of the work done by the current is converted into heat energy, reducing the motor's overall output power and efficiency.
D. The friction between the brush and the commutator (commutation ring) will also cause sparks, erosion, noise and other problems, thus affecting downstream products.
(2) Driving Principle of Brushless Motor
The driving principle of the brushless motor is based on electronic commutation and electromagnetic induction. Its structure consists of a stator winding and a permanent magnet rotor, eliminating the traditional brushes and mechanical commutator, and is controlled by an external driver. The driver has a built-in Hall sensor or encoder to detect the rotor position in real time, and accurately switches the stator winding power-on sequence based on the position feedback to form a rotating magnetic field and drive the permanent magnet rotor to rotate continuously. Compared with brushed motors, brushless motors have the advantages of high efficiency, long life, low maintenance, and low noise, and are widely used in new energy vehicles, home appliances, and industrial automation.
Compared with brushed motors, brushless motors have very obvious characteristics:
A. Brushless motors have higher conversion efficiency due to the lack of energy loss caused by brush friction, which greatly improves efficiency compared with traditional brushed motors.
B. Brushless motors have higher speeds, better response speeds and control performance, and we can control their speeds by adjusting electronic sensors.
C. Brushless motors can generate greater torque at lower speeds. This makes brushless motors advantageous in some applications that require high torque starting and low-speed operation.
D. Brushless motors have no wearable brushes (mechanical friction), which reduces failures and maintenance costs caused by brush friction.
E. Since there is no wear of mechanical brushes, brushless motors have longer and more durable service life, especially under high-speed operation and harsh environmental conditions, and have less operating noise.
F. Brushless motors are more compact and small in size, suitable for small equipment and compact space applications.
G. Superior control performance. Brushless motors use electronic commutation control, which can achieve precise speed control and torque control and have the ability to respond quickly.
(3) Classification of brushless motors
A. Outer rotor brushless DC motor: This outer rotor BLDC motor is basically the opposite of the inner rotor brushless motor type. It is also called an outer rotor brushless motor, which uses a rotating outer shell around a fixed inner part. Outer rotor BLDC motors usually use a higher number of permanent magnet poles on the rotor. This means greater torque and smoother operation. The main disadvantage of outer rotor brushless DC motors is slow speed. Therefore, these types of motors are more suitable for low-speed, high-torque applications.
B. Sensored brushless DC motor: A BLDC motor with Hall sensors is a motor that relies on sensors to provide rotor position data. These types of brushless motors provide reliable performance at lower speeds. At lower speeds, the sensor provides accurate data for smooth rotation. Sensored motors have problems with untimely feedback at higher speeds, and harsh conditions such as magnetic interference or high-temperature environments can also affect the sensor work, thereby affecting the operation of the motor.
C. Sensorless brushless DC motor: This type of motor does not use Hall sensors. Instead, the controller relies on the back EMF generated in the stator coils to calculate the rotor position. These types of brushless DC motors provide the best performance at high speeds. You can also use them in high-temperature environments because they do not use sensors. When the back EMF is too low or stationary to be read by the controller, the motor cannot be accurately controlled, so these motor types are suitable for high-speed, low-cost application environments.
D. Single-phase brushless DC motor: The rotor used by single-phase brushless motors consists of a pair of north and south poles. This type of brushless DC motor design has its advantages and disadvantages. The advantage is that the motor can reach very high rotation speeds at the beginning. On the downside, the performance of unipolar motors will drop significantly at lower speeds, affecting rotational stability and efficiency. Three-phase brushless motors use multiple magnetic poles on the rotor, up to 12 or more. As mentioned earlier, they are placed so that the opposite poles face each other. More magnetic poles provide smoother rotation, but at the expense of speed. Therefore, these types of brushless motors cannot reach high speeds and are suitable for low-speed, high-torque applications.
E. Sine wave drive brushless DC motor: Sine wave drives rotate the rotor by continuously changing the voltage of the stator coil in a sinusoidal manner according to the rotation angle of the rotor. The three phases of the motor will be "delayed" for a specific period of time, depending on the frequency.
F. Square wave drive brushless DC motor: Square wave drive is the simplest drive method. It switches the ON/OFF state of the electronic components according to the rotation angle of the rotor and then changes the current direction of the stator coil to rotate the rotor. The current direction switches 6 times for each rotation of the rotor.
(4) Technical barriers of brushless motors
As mentioned above, the realization of high efficiency, low noise, multi-functional complex control tasks, and the presentation of low noise and low vibration effects at high speed are all closely related to motor control. This control can be understood as the requirements of the main control IC at the hardware level and the requirements of the control algorithm at the software level. The two are inseparable.
The quality of the algorithm will definitely directly affect the control performance. The algorithm itself is constantly iterating and updating with the development of control technology. With the continuous improvement of control performance, the complexity of the algorithm also increases. The increase in algorithm complexity requires a significant increase in computing speed and computing volume. Therefore, the hardware indicators of the main control chip are now more and more demanding.
From the iteration of control methods of different application terminals, we can see that the trend is developing towards sensorless and FOC. Refrigerators were originally controlled by fixed frequency, but later they were mostly controlled by 120-degree square wave BLDC. Now sensorless FOC DC frequency conversion is the optimal solution. Washing machines were also controlled by fixed frequency at first, but later they were controlled by sensory SVPWM BLDC/DD, and now they are also controlled by sensorless FOC BLDC/DD. Hair dryers were originally controlled by series motors that did not require electronic control, but later they began to use BLDC to achieve stepless speed regulation, which is now also a very representative terminal application of FOC control. There are also electric balancing vehicles, which were originally controlled by three-phase BLDC sensory square wave, and later they were controlled by sensory FOC, and now they are also controlled by sensorless FOC.
From square wave control to SVPWM to FOC, from sensor to sensorless, the complexity of control algorithms has increased step by step, and the control performance of BLDC has also leaped step by step. The control algorithm of sensorless plus FOC is the most advanced, which can achieve high efficiency, low vibration, low noise and high response speed control effect to the greatest extent.
Sensorless brings a simpler layout to the entire motor control system and reduces the risk of sensor failure. FOC can achieve precision control goals such as higher efficiency, lower vibration, smaller noise, smoother torque control and faster dynamic response speed to the greatest extent. In today's world of high power density and compact design, sensorless and FOC are indeed more difficult but also more promising, and are the future technology development trend.
In order to achieve these complex calculations, the main control chip is also being upgraded. Now many chip manufacturers have developed a main control MCU dedicated to BLDC, and have also used their own chips to implement control-related algorithms, or integrated control-related modules and devices into the chip using hardware for control. This reflects the technical trend of hardware modularization of motor algorithms and integration of motor control devices.
The development of high integration is actually self-evident. The entire chip industry is developing towards high integration. The motor drive control chip has experienced a process from complete separation to integrated op amps and comparators, integrated pre-drivers, integrated power supplies and MOSFETs, and now fully integrated modules. High integration is a core development trend of BLDC chips.
The hardware modularization of control algorithms is also an inevitable development trend. The complexity of algorithms continues to increase, and the development threshold is getting higher and higher. The motor control solution is constantly upgrading. It is a more friendly choice to lower the development threshold through hardware algorithms. Moreover, after the algorithm is hardwareized, it can improve the sensitivity to parameters and effectively improve the computing speed of MCU chips. The computing speed is faster than pure software calculation. The modularization of algorithms greatly reduces CPU usage. For high-performance motor control, this trend will develop very quickly.
Of course, the performance of the main control chip itself also directly leads to the phenomenon that the performance output of motor control products is different. First of all, the main frequency of the main control chip is limited, which will not be able to achieve high-speed computing and increase bandwidth; secondly, the execution of the outer loop code is limited and cannot be executed faster, even if the inner loop code can be executed quickly through the hardware method provided by the original manufacturer, so the influence of the chip main frequency is also very large. Therefore, we also see that in high-performance motor applications, there are more and more high-frequency cores and dual-core control chips, which take into account both high-frequency computing power and high integration.
3. Application of Brushless Motor
(1) AGV/AMR brushless motors can be used in AGV/AMR designs for battery-powered, compact, lightweight equipment motion control. They have the following advantages: compact structure, maintenance-free, and long service life. The brushless Hall angle positioning method enables precise control and positioning. They have a wider speed range and greater torque, thus providing smoother motion control.
(2) Brushless motors for drones can be used in drone power units. Drones are usually equipped with multiple brushless motors to drive propellers. The thrust generated by the propellers enables the aircraft to take off, land, hover, and move forward. Compared with traditional brushed motors, brushless motors can have higher speeds, thereby increasing the flight speed and carrying capacity of drones. Brushless motors are compact and lightweight and have great stability and power conversion advantages.
(3) In automobile manufacturing the application of brushless motors in the automobile industry is also becoming more and more widespread. In automobiles, brushless motors can be used as generators and motors. As a generator, it can charge the car battery and provide electricity for the car. Compared with the traditional induction asynchronous motor used as a motor in conventional models, it can be used as a power source for the car to drive the car forward or backward. The most representative of them is the permanent magnet synchronous motor. As a type of brushless motor, the permanent magnet synchronous motor has high efficiency, small size, low noise and good control performance. It is widely used in mid-to-high-end electric vehicles, such as Tesla (using the permanent magnet synchronous motor + AC asynchronous motor mode), BYD's new models, etc.
(4) Household appliances Brushless motors are used in various household appliances, such as washing machines, refrigerators, range hoods, vacuum cleaners, air conditioners, etc., to improve energy efficiency and reduce noise.
The kitchen is full of electrical appliances, and household brushless DC motors are even more dazzling. For example, blenders, juicers, coffee machines, egg beaters, rice cookers, food processors, grain grinders, stand mixers, meat choppers, electric cutting knives and other household appliances.
White appliances refer to electrical products that can replace people's housework, including washing machines and dishwashers that can reduce people's housework pressure, as well as air conditioners and refrigerators that enrich the living environment and improve the quality of life. Air conditioners, refrigerators, microwave oven cooling fans, range hoods, dishwashers, washing machine hot water pumps, etc. all have brushless motors inside.
When using household equipment, you can also use DC brushless motors, such as exhaust fans, electric heaters, etc. There are also circulating fans, humidifiers, dehumidifiers, air fresheners, air coolers, soap dispensers, hand dryers, smart door locks, electric doors, windows, curtains, etc. The quality of these smart home products is guaranteed.
Floors are also the main place and object for household cleaning and cleaning, and various electric floor cleaning products are also increasing, such as: carpet cleaners, electric vacuum cleaners, handheld vacuum cleaners, floor grinders, etc.
(5) Industrial Equipment
In industrial automation equipment, brushless motors are widely used in various robotic arms, conveying equipment, CNC machine tools, fans, etc. to achieve precise control and efficient operation.
Synchronous permanent magnet AC servo motors are widely used in the feed servo control of high-precision machine tool CNC equipment, and the momentum to replace wide-speed DC servo motors is strong. In recent years, permanent magnet AC linear servo motors are used in the feed servo control of new generation CNC machine tools, and synchronous permanent magnet AC servo motors are used instead of variable frequency induction motors as the main spindle direct drive motors of machine tools to improve the rapidity and processing efficiency of CNC machine tools, which has also become a new research and application feature.
In the drive of military and industrial robots and manipulators, the application of brushless DC motors is quite extensive, which has become one of the main application areas of brushless DC motors. High-power brushless DC motors (generally using thyristors as power devices, usually called commutatorless motors) have broad application prospects in low-speed, harsh environments and occasions with certain speed regulation performance requirements, such as steel mill rolling mills, cement kiln transmission equipment, pumped storage units, etc.
The latest generation of elevator gearless traction machines that have appeared in recent years are elevator drive devices that use synchronous permanent magnet AC servo motors as power, magnetic field oriented vector control and fast current tracking control. Compared with gear-driven DC traction machines and AC traction machines driven by induction motors, it has better control performance and has the advantages of high efficiency, low noise, small size, and light weight. It has been quickly valued by internationally renowned elevator companies, and they have developed their own gearless traction machine elevators and pushed them into the high-end market. Gearless direct-driven brushless traction machines have caused a revolutionary change in elevators, and small machine rooms and machine room-less elevators have emerged.
(6) Medical Devices
In medical equipment, brushless motors are used in surgical instruments, injection pumps, ventilators, etc. to achieve precise motion control and low-noise operation.
Brushless servo motors can be used in drive systems in surgical instruments, such as surgical robots, surgical forceps, dissectors, etc. These instruments require high-precision and high-speed motion control, and brushless servo motors can provide precise position and speed control. Similarly, brushless servo motors can be used in rotating platforms, lifting mechanisms, and focusing mechanisms in medical imaging equipment. For example, CT scanners, X-ray machines, MRI machines, and other equipment all require accurate motion control to achieve image acquisition and adjustment.
In infusion pumps and syringes, brushless servo motors can be used for flow control and precise drug delivery in medical equipment such as infusion pumps and syringes. By controlling the speed and position of the motor, precise flow regulation and drug dosage control can be achieved.
When it comes to the field of ventilators and anesthesia machines, brushless servo motors can be used for airflow control and pressure regulation in ventilators and anesthesia machines. Through precise control of the motor, stable airflow output and accurate pressure adjustment can be achieved to meet the needs of patients.
Finally, in rehabilitation equipment, brushless servo motors can be used in rehabilitation equipment such as electric wheelchairs, prostheses, and exoskeletons. These devices need to provide precise motion control and force support, and brushless servo motors can meet these requirements.
(7) Power tool brushless motors are widely used in various power tools, such as electric drills, electric hammers, electric wrenches, etc. to provide efficient power output.
Taking the electric drill as an example, ordinary brushed motors use brushes to contact the power supply, which will have a greater impact on the efficiency of the motor, while brushless motors do not have this impact. Since brushless motors have no brushes and no friction loss, their efficiency is much higher than that of traditional brushed motors.
The structure of the brushless motor for electric drills is much simpler than that of traditional brushed motors. Since it has no brushes and no friction loss, its structure is also more compact, which can reduce the size of the electric drill and make it more practical; there is no friction loss, and the service life is much longer than that of traditional brushed motors, which can meet the requirements of various application scenarios, such as long-term continuous operation, and can also provide more reliable power drive; the fully enclosed structure can effectively reduce noise, which is one of the reasons for its large-scale application.
Since brushless motors have no brushes and no friction loss, electric drills using brushless motors can effectively save energy, saving 30%-50% of electricity compared to brushless motors, thereby effectively reducing the operating costs of electric drills.
4. Size of the Brushless Motor Market
(1) Market Overview
According to the BLDC research statistics released by Grandview Research, the global brushless DC motor market size was US$18.8254 billion in 2022, and the market size is expected to be US$19.8638 billion in 2023, and will grow at a compound annual growth rate of 6.5% to US$30.8624 billion in 2030.
The sub-750 watt segment dominated the market in terms of revenue, accounting for 48.5% share in 2022. This high share is attributed to the widespread use of these products in numerous applications such as fans, pumps, compressors, machine tools, home appliances, electric vehicles, HVAC applications, power tools, and automation robots. The growing demand for fractional power brushless DC motors in various machinery in the agricultural sector in my country and India is further driving the product demand.
The above 75 kW segment is also expected to witness substantial growth from 2023 to 2030. This is owing to the advantages such as better performance in terms of efficiency and reliability compared to conventional DC motors with the same rated output power. These brushless DC motors are used in various industrial applications such as milling, drilling, and grinding, deployed in industrial machinery such as CNC machine tools. In addition, increasing consumer awareness and government policies for energy conservation will also drive the market during the forecast period.
(2) Global Market Distribution
From the perspective of the market structure, Asia and Oceania account for the largest share of the brushless DC motor market, accounting for 49.6%, followed by the United States, accounting for 21.08%. In fact, there are many brushless DC motor companies with good technical strength in Asia, but they are mainly concentrated in Japan, such as Nidec, Panasonic, Minebea, Sanyo Electric, etc. As for China, it is still in the catching-up stage. However, it is foreseeable that the future growth of brushless DC motors will mainly come from Asia, and Asia will mainly be in China.
Europe also has a large market share of about 19%. Since Europe and the United States started earlier, they have mastered many core technologies of brushless DC motors. In the future, as the global market demand for high-end brushless DC motors increases, the share of the European and American markets will also grow slowly. But the proportion is definitely not as high as that in Asia.
In order to effectively meet the needs of the growing population, there is an urgent need to increase power generation capacity, which has driven the adoption of these motors in many applications in the Middle East. The untapped potential of downstream activities in developing countries such as Kuwait, the UAE and Qatar provides new growth avenues for the market from 2023 to 2030. The North American and European regional markets together accounted for more than 37% of the overall market share in 2022. The growth in the region is attributed to the increased preference for brushless DC motors due to the growing popularity of motor vehicles in the region, which is expected to further stimulate market growth during the forecast period.
Since its invention, brushless motors have been plagued by technical, cost, and process problems, and did not gradually get out of the predicament until the beginning of the 21st century. When technical problems are gradually solved, brushless motors will gradually be recognized by all walks of life for their excellent performance and characteristics, prompting a rapid increase in the market share of brushless motors and their derivative products.
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