Brushless motor is a synchronous motor that uses DC power supply and realizes commutation function through electronic commutator without carbon brush and commutator, thus avoiding friction loss, spark interference and maintenance costs. Brushless motor has the advantages of high efficiency, high performance, low noise, low vibration, long life and high reliability. This paper introduces the classification of brushless motors.Classification of Brushless DC Motors1. External rotor brushless DC motor: This external rotor BLDC motor is basically the opposite of the type of internal rotor brushless motor. Also known as an external rotor brushless motor, it uses a rotating housing around a fixed internal component. External rotor BLDC motors typically use a higher number of permanent magnet poles on the rotor. This means more torque and smoother operation. The main disadvantage of the external rotor brushless DC motor is its slow speed. As a result, these types of motors are better suited for low-speed, high-torque applications.2. Inductive brushless DC motor:BLDC motor with Hall sensor is a motor that relies on the sensor to provide rotor position data. These types of brushless motors provide reliable performance at lower speeds. At lower rotational speeds, the sensor provides accurate data for smooth rotation. The motor with sensor will have the problem of delayed feedback at higher speeds, and harsh conditions such as magnetic interference or high temperature environment will also affect the sensor work, thus affecting the motor operation.3.  Sensorless brushless DC motor: This type of motor does not use Hall sensors. Instead, the controller relies on the back electromotive force generated in the stator coil to calculate the rotor position. These types of brushless DC motors offer the best performance at high speeds. You can also use them in high temperature environments because they do not use sensors. When the back electromotive force is too low or at rest to be read by the controller, the motor cannot be accurately controlled, so these motor types are suitable for high-speed, low-cost applications.4.  Single-phase brushless DC motor: the rotor used by the single-phase brushless motor is composed 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 initially reach a very high rotation speed. On the downside, the performance of unipolar motors decreases significantly at lower speeds, which affects 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 applications with low speeds and high torque.5.  Sine wave drive brushless DC motor: sine wave driver rotates 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 "delay" for a specific amount of time, depending on the frequency.6.  Square wave drive brushless DC motor: square wave drive is the simplest way to drive. It switches the ON/OFF state of the electronic components according to the rotation Angle of the rotor, and then changes the direction of the current in the stator coil, thus making the rotor rotate. The rotor rotates once and the current direction changes 6 times.ConclusionSince the invention of the brushless motor, it has been plagued by technology, cost, process and other problems until the beginning of the 21st century. When the technical problems are gradually solved, the brushless motor with its excellent performance and characteristics will gradually be recognized by all walks of life, and the market share of brushless motor and its derivative products will grow rapidly.

Before understanding the working principle of brushless motors, let's first learn the right-hand screw rule two (ampere rule two), as shown in the following figure:When we hold the solenoid with the right hand, the four fingers point to the direction of the current, then the end pointed by the thumb is the N pole of the solenoid, and if the current is in the opposite direction, the north and South Pole are switched positions.As shown in the figure above, we wind the stator around the coil and pass a certain current through the coil to generate a magnetic field. Lorentz's law of force states that as long as a current-carrying conductor is placed in a magnetic field, it will experience a force. Due to the reaction force, the magnet will experience equal and opposite forces. When the coil through the current, will produce a magnetic field, the magnetic field is driven by the stator's magnetic pole, the same pole repel each other, the opposite pole attracts each other, if you continue to change the direction of the coil current, then the rotor induced by the magnetic field of the magnetic pole will continue to change, then the rotor will be rotating under the action of the magnetic field.The switching sequence of the current is mainly realized by the Hall sensor, which is mainly used to determine the conduction Angle of the power transistor in the electronic commutation circuit drive circuit, so as to determine the magnetic state of the armature field. The position of the pole of the rotor permanent magnet relative to the stator armature winding is detected by it so as to determine the switching sequence of the power transistor in the electronic commutation drive circuit.In addition to Hall magnetic sensors, brushless motors can also use other sensors, such as photoelectric and electromagnetic sensors. 

Structural AspectBrushless DC Motor: consists of a motor body and a driver, including a rotor, a stator, a sensor and an electronic controller. There is no brush and commutator, relying on the electronic controller to control the direction and size of the current in the stator winding according to the rotor position information detected by the sensor to realize the rotation of the rotor.Brush DC Motor: mainly composed of a stator (usually a permanent magnet), a rotor (composed of winding), a brush and a commutator. The brush and commutator change the direction of the current through mechanical contact, so that the rotor continues to rotate.Performance AspectBrushless DC Motor: higher efficiency, generally 85%-90%, more stable operation, low noise, almost no electrical spark, electromagnetic interference is small, due to the reduction of mechanical wear parts, long service life.Brush DC Motor: the starting speed is fast, the torque is large, but the mechanical friction between the brush and the commutator will lead to greater noise and heat during high-speed operation, and will also produce electrical sparks, which may cause electromagnetic interference to other equipment, and the efficiency is generally 75%-80%.Control AspectBrushless DC Motor: requires a complex electronic control unit to achieve accurate commutation control, usually using digital control technology, according to the rotor position sensor feedback information, precisely control the current in the stator winding on and off and order.Brush DC Motor: The control is relatively simple, by adjusting the size and direction of the DC voltage applied to both ends of the brush, you can control the speed and steering of the motor, which can be controlled by traditional analog circuits such as thyristor.Application AspectBrushless DC Motor: suitable for applications requiring high efficiency, noise, life and control accuracy, such as drones, electric vehicles, industrial automation equipment, high-end home appliances, etc. Brush DC Motor: Often used in cost-sensitive, precision requirements are not high, the need for large starting torque occasions, such as electric toys, some traditional power tools, small appliances, etc. Cost AspectBrushless DC Motor: Due to the need for components such as electronic controllers and position sensors, and high manufacturing process and material requirements, manufacturing costs are high.Brush DC Motor: simple structure, mature production process, low manufacturing cost. 

1. Cannot start or the speed is low1) The circuit breaker is faulty and the gate cannot be closed.Analyze and deal with the closing power supply and closing circuit faults.2) The relay malfunctioned.If the vibration or set value of the relay is small, check the relay.3) One phase of the stator winding or the main circuit is open.Check and measure the stator winding and mainline after a power failure, find out the breaking point and repair it.4) The load is too heavy or the machinery being pulled is faulty.Check the motor load and the machinery being pulled. 2. Not synchronized after startup1) The grid voltage is low.Check grid voltage.2) The auxiliary contact of the circuit breaker connected to the excitation device is poorly closed.Check the power outage and repair the auxiliary contacts of the circuit breaker.3) The rotor circuit is in poor contact or open circuit.Measuring the resistance of the rotor circuit should meet the requirements, and carry out fastening inspection.4) The brushless excitation system is faulty, the silicon tube is damaged and there is no output.Replace the silicon tube. 3. Out of step during operation1) The power grid voltage is low, and the out-of-step setting thyristor device is out of control.Check the SCR out-of-step protection device.2) The excitation voltage is reduced.Shut down and check the excitation device.3) The mechanical load is too heavy.Shutdown to check mechanical load.   4. Sparks and smoke appear in the air gap1) The shaft center is not correct or the bearing bush is worn so that the stator and the rotor rub against each other.Shut down to check the air gap between the stator and rotor and make corresponding repairs according to the situation.2) The rotor is broken or the short circuit ring is desoldered.Stop the machine to find out the break point or re-weld the poor contact part.3) Turn-to-turn short circuit or phase-to-phase short circuit of the stator winding; rotor coil disconnection or grounding.Pull the core to check and replace the faulty coil.5. Overheating during operation1) OverloadReduce the mechanical load so that the stator current does not exceed the rated value, monitor the system voltage, current, and    power factor, and adjust in time.2) The insulation between the stator core silicon steel sheets is poor or there are burrs.Shut down to overhaul the stator core.3) There is a short circuit or ground fault in the stator winding.Find the faulty coil and repair or replace it.4) The ambient temperature is too high and the motor is not well ventilated.Check whether the air duct is unblocked, whether the fan is in good condition, and whether the rotation direction is correct.5) The water cooler has no water or the water volume is very small.Check whether the water cooling system is normal.    6. Accident parking1) Cable or cable head wiring failure.Find out the fault point for overhaul.2) The stator winding is short-circuited or grounded between phases.Find the short circuit or grounding point, deal with the faulty coil, and the withstand voltage is qualified.3) The secondary circuit of the current transformer is faulty.Check the secondary circuit of the current transformer, deal with disconnection or poor contact, and verify the volt-ampere    characteristic curve of the current transformer.4) The relay malfunctions.Re-check relay settings and adjust relays.5) The shaft of the motor is locked or the dragged machinery is stuck.Find and fix mechanical problems.6) The excitation device or excitation circuit is faulty.Check and debug the excitation device to eliminate poor contact of the excitation circuit.7) Process interlocking action.Judging the action part of the process interlocking device, finding out the cause, eliminating it and doing a simulation test.7. Severe vibration1) Poor mechanical alignment.Re-align and meet technical requirements.2) The bearing is damaged.Replace motor bearings.3) The static balance and dynamic balance of the rotor are unqualified.Adjust the dynamic and static balance of the rotor.4) The foundation of the motor is uneven and the anchor screws are loose.Check the foundation level and tighten the anchor screws. 

Advantages:1. Compact design and high transmission efficiencyPlanetary gear motors are compact, have high power density, are small and lightweight, and are highly efficient and precise. Its design virtually eliminates recoil and ensures precise motion control.2. Excellent torque transmissionPlanetary gear motors share the load through multiple planetary gears and perform particularly well in applications requiring high torque. Its drive train delivers strong torque output in a stable manner for high load and high demand scenarios.3. High reliability and long lifeThe planetary gear system has been carefully designed to minimize gear misalignment and vibration problems. Its low noise level, excellent repeatability and stable operating performance greatly enhance the reliability and durability of the motor for long-term operation.Disadvantages:1. Higher cost and complex designCompared to other types of motors, planetary gear motors are usually more expensive because of their complex mechanical design and the high level of manufacturing precision required. In addition, maintenance may require more specialized technical support, resulting in higher overall costs.2. Potential operating noise and maintenance difficultiesWhile planetary gear motors are typically quieter, vibration and noise may become more noticeable under high loads or complex operating conditions. In addition, their complex construction can present maintenance and repair challenges.

Micro DC motors are a type of small motors, usually referring to motors with a diameter between a few millimeters and tens of millimeters, small size, and high power. This kind of motor can not be realized without the support of microtechnology, and it can be widely used in automation equipment, medical equipment, aerospace, robotics, smart homes, and other fields. The advantage is that they can be better adapted to the needs of miniaturized devices. Taking portable devices such as cell phones as an example, can provide them with strong power support and help them fulfill various functions. In addition, their small size, light weight, and low energy consumption enable them to adapt to more stringent working conditions, while also reducing equipment costs and energy consumption. Their structure can be divided into four parts: rotor, stator, magnet, and circuit. The rotor usually consists of an iron core, shaft, bearing, guide plate, and winding; the stator consists of the iron core, coil, conductor, and so on. The magnet is an important part, which serves to form a magnetic field between the stator and rotor to convert electrical energy into mechanical energy. The circuit plays the role of controlling and transmitting electrical energy, mainly including power supply, switch, sensor, integrated circuit, etc.There are many micro motors in automobiles. With the popularity of electric vehicles and the improvement of various configurations, more micro motors are used in automobiles. Typically, a car is equipped with an automotive generator and multiple automotive micro motors (15-20 on average), while high-end luxury sedans require 60-70 micro motors, and high-end new energy vehicles require hundreds. An automotive air conditioning system can drive various valves in the automotive air conditioning system to control the direction and temperature of airflow to meet the driver's comfort needs. Compared with the traditional pneumatic drive method, there is no need to add complex piping and air circuits, which saves more space and energy. Car Seat Adjustment System can be used to drive car seat adjustment systems, such as seat height, backrest tilt angle, headrest height, etc. In these systems, it can provide more precise control and adjustment ability, bringing a more comfortable experience to the driver. The window lift system can provide power support for the window lift system, making window operation more convenient and easy. Compared with the traditional manual operation, it can make the window lifting and lowering smoother and faster, and also avoid the window shaking or jamming. Car mirror adjustment system also plays an important role in car mirror adjustment system. Driven by a motor, the driver can easily adjust the mirrors electronically to make them more customized to the driver's individual needs. Therefore, you can find out the number of micro motors in the car configuration and roughly determine the low and comfortable luxury level of the car configuration!Engine part: mainly applied in the automobile starter motor, EFI control system, engine water tank radiator, generator, and these parts.Automotive chassis frame: chassis frame micromotors are used in electronic suspension control systems, dynamic power steering, automotive stability control systems, cruise control systems, anti-lock lock control systems, and drive power control applications. Most use permanent magnet DC motors or permanent magnet stepper motors.Body parts: such as central door locking device, power mirrors, automatic lifting antenna, power sunroof, automatic headlights, HUD, air-conditioning door control, automatic window lifter, window anti-pinch device, power wipers, power tailgate, power seats, and other auto parts.