China's automotive motors have obvious comparative advantages under global resource conditions and have great development potential. From the perspective of the industry chain of new energy vehicles, the beneficiaries will mainly focus on the core parts and components. The status quo of the domestic vehicle drive motor industry: a small industry in the motor industry, but the manufacturing threshold is high, and there are still many gaps and deficiencies in the motor drive system, but domestic policy support will accelerate the pace of the industry. As one of the core components (battery, motor, and electronic control) of new energy vehicles, as shown in Figure 1, the future development prospects of the drive motor and its control system are promising. 

Introduction to drive motor system

  New energy vehicles have three major advantages: environmental protection, saving, and simplicity. It is especially evident in pure electric vehicles: an electric motor is used instead of a fuel engine, driven by an electric motor without an automatic transmission. Compared with the automatic transmission, the motor has simple structure, mature technology and reliable operation. The speed at which a traditional internal combustion engine can efficiently generate torque is limited to a narrow range, which is why traditional internal combustion engine vehicles require a large and complex transmission mechanism; while an electric motor can efficiently generate torque in a fairly wide speed range, During the running of the pure electric vehicle, there is no need for a gear shifting device, the operation is convenient and easy, and the noise is low.

  Compared with hybrid electric vehicles, pure electric vehicles use a single electric energy source, and the electronic control system greatly reduces the mechanical transmission system inside the car, the structure is more simplified, and the energy loss and noise caused by the friction of mechanical parts are also reduced, saving the interior space of the car, weight. The motor drive control system is the main execution structure in the driving of new energy vehicles. The drive motor and its control system are one of the core components (battery, motor, and electronic control) of new energy vehicles. The driving characteristics determine the main performance of the vehicle. indicator, which is an important part of electric vehicles. The fuel cell vehicle FCV, hybrid vehicle HEV and pure electric vehicle EV in electric vehicles all use electric motors to drive the wheels. Selecting a suitable electric motor is an important factor to improve the cost performance of various electric vehicles. Therefore, research and development or improvement of energy At the same time, it is extremely important to meet the performance requirements of the vehicle during driving, and to have a motor drive mode with the characteristics of durability, low cost, and high efficiency. 

The drive motor system is one of the three core components of new energy vehicles. The motor drive control system is the main execution structure in the driving of new energy vehicles. Its driving characteristics determine the main performance indicators of the vehicle. It is an important part of the electric vehicle. The entire drive system of an electric vehicle includes two parts: the motor drive system and its mechanical transmission mechanism. The motor drive system is mainly composed of motors, power converters, controllers, various detection sensors, and power supplies. The structure is shown in Figure 2 below. The motor is generally required to have two functions of electric motor and power generation. According to the type, several motors such as DC, AC, permanent magnet brushless or switched reluctance can be selected, as shown in Figure 3. According to the type of motor selected, the power converter has the form of DC/DC power converter, DC/AC power converter, etc. Its function is to convert the DC power of the battery into DC and AC power of the corresponding voltage level according to the drive current requirements of the selected motor. or pulse power. 

The motor is a rotating electromagnetic machine that operates on the principle of electromagnetic induction, and is used to convert electrical energy into mechanical energy. During operation, it absorbs electric power from the electrical system and outputs mechanical power to the mechanical system. The motor drive system is mainly composed of a motor and a controller (inverter). The cost ratio of the drive motor and the motor controller is about 1:1. According to different design principles and classification methods, the specific structure and cost composition of the motor There are also differences. The control system of the motor mainly plays the role of adjusting the running state of the motor to meet the different running requirements of the whole vehicle. For different types of motors, the principles and methods of the control system are very different.

Figure 2 The basic composition block diagram of the motor drive system

Figure 3 Classification of motors (according to principles) The basic requirements of electric vehicles for drive motors Compare the application, advantages and disadvantages of four commonly used motor drive systems. 

1. The basic requirements of electric vehicle motors are as follows:

  (1) The motor has compact structure, small size, and limited package size, so it must be specially designed according to specific products.

(2) Light weight to reduce the overall weight of the vehicle. The aluminum alloy shell should be used as much as possible, and the speed should be high at the same time to reduce the weight of the vehicle, increase the adaptability of the motor and the body, and expand the available space of the body, thereby improving the comfort of the ride.

(3) High reliability and controllable failure modes to ensure the safety of passengers.

(4) Provide precise torque control and good dynamic performance.　　

(5) High efficiency and high power density. It is necessary to ensure high efficiency in a wide speed and torque range to reduce power loss and increase the mileage of a single charge.

(6) Low cost to reduce the overall cost of vehicle production.

(7) Wide range of speed regulation. It should include a constant torque area and a constant power area. The constant torque output by low-speed operation is large to meet the requirements of rapid start, acceleration, and load climbing of the car; high-speed operation outputs constant power and has a large speed adjustment range to meet Flat road, overtaking and other high-speed driving requirements.

(8) The instantaneous power is large and the overload capacity is strong. It is necessary to ensure that the car has an overload capacity of 4 to 5 times to meet the requirements of acceleration and maximum climbing in a short period of time.

(9) Good environmental adaptability. To adapt to the different regional environments where the car itself drives, it can work normally even in a harsh environment, and has good high temperature resistance and humidity resistance.

(10) High braking regeneration efficiency. When the car decelerates, it can realize regenerative braking, recover energy and feed it back to the battery, so that the electric car has the best energy utilization rate.

(11) Others. Simple structure, low price, suitable for mass production, low noise during operation, convenient use and maintenance.

(12) Different from general industrial motors, driving motors used in automobiles should have the characteristics of wide speed range, large starting torque, high backup power, and high efficiency. In addition, high reliability, high temperature resistance and moisture resistance are also required. The structure is simple, the cost is low, the maintenance is simple, and it is suitable for large-scale production. In the future, the driving motor system for electric vehicles in my country will develop in the direction of permanent magnetization, digitalization and integration.

  2. Application of asynchronous motor (induction motor) in new energy vehicles

  (1) Introduction to asynchronous motors Induction motors are also called "asynchronous motors", that is, the rotor is placed in a rotating magnetic field, and under the action of the rotating magnetic field, a rotational torque is obtained, so the rotor rotates. The rotor is a rotatable conductor, usually in the shape of a squirrel cage. The stator is the non-rotating part of the motor whose main task is to generate a rotating magnetic field. Rotating magnetic fields are not achieved mechanically. Instead, alternating current is passed through several pairs of electromagnets to make the magnetic pole properties change cyclically, so it is equivalent to a rotating magnetic field. This motor does not have brushes or slip rings like a DC motor. There are single-phase motors and three-phase motors depending on the type of AC power used.

  (2) Characteristics of asynchronous motors Asynchronous motors have the following advantages: compact structure, sturdy and durable; reliable operation, convenient maintenance; low price, small size, light weight; good environmental adaptability; low torque ripple and low noise. AC asynchronous motors are low in cost and high in reliability. Even if the inverter is damaged and a short circuit occurs, it will not generate back electromotive force, so there will be no possibility of sudden braking. Therefore, it is widely used in large and high-speed electric vehicles. The power capacity of the three-phase cage asynchronous motor covers a wide range, from a few tenths of a watt to several kilowatts. It can be air-cooled or liquid-cooled, with high cooling freedom, good adaptability to the environment, and regenerative braking. Compared with the DC motor of the same power, the efficiency is higher and the weight is about half lighter. At the same time, it has the following disadvantages: low power factor, must absorb reactive current from the grid to establish a magnetic field during operation; complex control, easily affected by motor parameters and load changes; rotor is not easy to dissipate heat; poor speed regulation performance, narrow speed regulation range . Advantage analysis: The electric motor dedicated to new energy vehicles generates action by obtaining limited energy from the battery, so it is required to have good efficiency in various environments. Therefore, the performance requirements are more stringent than those of general industrial motors. A motor suitable for electric vehicles needs to meet several characteristics: small size and light weight (sturdyness) due to high speed, high efficiency (long driving range after a single charge), wide range at low speed and high torque Constant output characteristics, long life and high reliability, low noise and low cost. However, in reality, a motor that satisfies the above characteristics has not yet been developed. At present, the motors that are more suitable for new energy vehicles are AC asynchronous motors and PM motors.　

(3) The control system of the asynchronous motor Since the AC three-phase induction motor cannot directly use DC power, an inverter device is required for conversion control. When the new energy vehicle decelerates or brakes, the motor is in the state of generating and braking, charging the battery to realize the conversion of mechanical energy into electrical energy. In new energy vehicles, the PWM power inverter composed of power semiconductor devices converts the DC power provided by the battery power supply into AC power with adjustable frequency and amplitude. The control methods of three-phase asynchronous motor inverter mainly include V/f constant control method, slip rate control method, vector control method and direct torque control method (DTC). Before the 1990s, the first two control methods were mainly used. However, due to the small speed control range and unsatisfactory torque characteristics, they are not suitable for electric vehicles that require frequent starting, acceleration and deceleration. Now, the latter two control methods are currently in the mainstream.

  (4) Application status of asynchronous motors In the United States, asynchronous motors are widely used, which is also considered to be related to road conditions. In the United States, highways already have a certain scale. Except for big cities, cars generally continue to drive at a certain high speed, so asynchronous motors that can achieve high-speed operation and have higher efficiency at high speeds are widely used. In my country, with the development of highway scale, the application of AC asynchronous motors in new energy vehicles will become more and more important. 

3. Application of permanent magnet brushless motor in new energy vehicles

  With the rapid development of power electronics technology, microelectronics technology, microcomputer technology, rare earth permanent magnet materials, sensor technology and motor control theory in recent years, AC drive technology has gradually matured. Compared with the existing series-excited or shunt-excited brushed DC motor drive system, the permanent magnet brushless motor has the advantages of high power density, small size, high efficiency, simple and firm structure, and easy maintenance. The operation and maintenance cost of the electric vehicle drive system of the drive components is low; the fully digital and modular structure design makes the drive interface flexible, the control ability is stronger, and the operation is more comfortable; the application of energy feedback braking technology can reduce the wear of brake pads , and at the same time increase the mileage of the car. Therefore, based on the development needs of the electric vehicle market and the current state of technology, it is of great practical significance to design and develop a reliable, low-cost, and high-performance full-digital electric vehicle permanent magnet brushless motor drive system for the development of the electric vehicle industry.

  (1) Brief introduction of permanent magnet synchronous motor There are two methods to establish the air gap magnetic field necessary for electromechanical energy conversion in the motor. One is to pass current in the motor windings to generate a magnetic field. This method requires not only special windings and corresponding devices, but also continuous energy supply to maintain current flow, such as ordinary DC motors and synchronous motors. The other is to generate a magnetic field by a permanent magnet, which can simplify the structure of the motor and save energy. A motor whose magnetic field is generated by permanent magnets is a permanent magnet motor. It uses permanent magnets to establish a synchronous motor with an exciting magnetic field, its stator generates a rotating magnetic field, and the rotor is made of permanent magnetic materials. In order to realize the conversion of energy, the synchronous generator needs a DC magnetic field to generate the DC current of this magnetic field, which is called the excitation current of the generator. According to the supply method of excitation current, any generator that obtains excitation current from other power sources is called an externally excited generator, and a generator that obtains excitation power from the generator itself is called a self-excited generator. 

(2) Characteristics of permanent magnet synchronous motor Permanent magnet synchronous motor has the following advantages: large power factor, high efficiency, high power density; simple structure, easy maintenance, long service life, high reliability; good speed regulation performance, high precision It has good transient characteristics, low moment of inertia and fast response; high frequency, large output torque, limit speed and braking performance are better than other types of motors; electronic power devices are used as commutation devices, and the drive is flexible and controllable Strong; the shape and size are flexible and diverse, which is convenient for shape design; the motor is small in size and light in weight after using rare earth permanent magnet materials. However, the permanent magnet synchronous motor also has the following disadvantages: the motor cost is high; in the constant power mode, the operation is more complicated, and the control system cost is higher; the magnetic field weakening ability is poor, and the speed regulation range is limited; Influence and limitation, the maximum power is only tens of kilowatts; the rated current is large at low speed, the loss is large, and the efficiency is low; when the permanent magnet material is subjected to vibration, high temperature and overload current, its magnetic permeability may decline or demagnetization The phenomenon will reduce the performance of the permanent magnet motor, and even damage the motor in severe cases. It must be strictly controlled during use to prevent it from being overloaded. The magnetic field of the permanent magnet material is immutable. If you want to increase the power of the motor, its volume will be large; its corrosion resistance is poor; it is not easy to assemble. 

(4) Control system of permanent magnet synchronous motor The control technology of permanent magnet motor is similar to that of induction motor, and the control strategy mainly focuses on improving low-speed torque characteristics and high-speed constant power characteristics. At present, permanent magnet synchronous motors often use vector control at low speeds, including air gap magnetic field orientation, rotor flux orientation, stator flux orientation, etc.; while at high speeds, permanent magnet synchronous motors usually use field weakening control. 

(5) Application status of permanent magnet motor The design theory, calculation method, detection technology and manufacturing process of rare earth permanent magnet motor are constantly being improved and developed, and the performance and reliability of permanent magnet materials are constantly improving. The rapid development of power electronics technology, large-scale integrated circuits and computer technology has also played a positive role in promoting the development of permanent magnet drive motors. With the rapid development of hybrid electric vehicles and pure electric vehicles in the future, permanent magnet drive motors will usher in a more rapid development period, and their development trends will also present the following characteristics: high power density, high torque density, high controllability Sex, high efficiency, high performance, high price ratio, etc., to meet the actual needs of hybrid electric vehicles and pure electric vehicles. 

4. Application of switched reluctance motor in new energy vehicles

(1) Introduction to Switched Reluctance Motor Switched Reluctance Drive (SRD) is the latest generation of stepless speed regulation system developed after frequency conversion speed regulation system and brushless DC motor speed regulation system. It is a collection of modern microelectronics Technology, digital technology, power electronics technology, infrared photoelectric technology and modern electromagnetic theory, design and production technology are integrated high-tech of light, machinery and electricity. It has the advantages of both DC and AC speed control systems in the speed control system.

  Switched reluctance motors cover various high and low speed drive speed control systems with a power range of 10W~5MW. The switched reluctance motor has many potential fields, and it can be widely used in various occasions that require speed regulation and high efficiency (electric vehicle drive, general industry, household appliances, textile machinery, electric drive system, etc.). Working principle of switched reluctance motor: The operation of switched reluctance motor follows the "minimum reluctance principle" - the magnetic flux always closes along the path with the least reluctance. When the iron core with a certain shape moves to the minimum reluctance position, its main axis must coincide with the axis of the magnetic field.

  (2) Features of switched reluctance motor Its structure is simpler than any other motor. There are no slip rings, windings and permanent magnets on the rotor of the motor, but there are simple concentrated windings on the stator. The ends of the windings are Shorter, no phase-to-phase jumper, easy maintenance and repair. Therefore, the reliability is good, and the speed can reach 15000 r/min. The efficiency can reach 85% to 93%, which is higher than that of the AC induction motor. The loss is mainly in the stator, and the motor is easy to cool; the rotor is composed of permanent magnets, which is easy to achieve various special torque-speed characteristics, and maintains high efficiency in a wide range. It is more suitable for the power performance requirements of electric vehicles.

  The switched reluctance motor also has the advantages of high-efficiency operation in a wide speed and torque range, flexible control, four-phase operation, fast response, and low cost. Good manufacturability, suitable for high speed, strong environmental adaptability; the direction of motor torque has nothing to do with the direction of winding current; suitable for frequent start and stop and forward and reverse conversion operation; small starting current, large torque; many controllable parameters, Good speed regulation performance; strong regenerative braking capability; both the stator and rotor are made of silicon steel sheets, which are easy to obtain and recycle. However, the switched reluctance motor has the disadvantages of large torque fluctuation, the need for a position detector, and the nonlinear characteristics of the system. The position detector is a key component of the switched reluctance motor, and its performance has an important influence on the control operation of the switched reluctance motor. Since the switched reluctance motor is a doubly salient pole structure, there is inevitably torque fluctuation, and noise is the main shortcoming of the switched reluctance motor. However, research in recent years has shown that the noise of switched reluctance motors can be well suppressed with reasonable design, manufacturing and control technologies. In addition, since the output torque of the switched reluctance motor fluctuates greatly, the DC current of the power converter also fluctuates greatly, so a large filter capacitor needs to be installed on the DC bus. 

(3) Switched reluctance motor control system The core of the switched reluctance motor drive system is the switched reluctance motor (SRM), which involves multidisciplinary knowledge such as motors, power electronics, microcomputers, control, photoelectric conversion, angle measurement, etc. The structure is relatively complex, and the control system requirements are relatively unique. The control methods of induction motors and permanent magnet synchronous motors are usually difficult to meet the control requirements of the system. At present, there are few applications of electric vehicles. Its main research direction is model research. Because the switched reluctance motor has obvious nonlinear characteristics, the system is difficult to model, and the general linear control method is not suitable for the switched reluctance motor system. At present, fuzzy logic control and neural network control are mainly used. Its control system includes power converters, controllers, position sensors and speed detectors. ① The excitation winding of the switched reluctance motor of the power converter, no matter through the forward current or the reverse current, its torque direction remains unchanged, and the phase commutation, each phase only needs a power switch tube with a small capacity, the power converter circuit It is relatively simple, there will be no through failure, good reliability, easy to realize the soft start and four-quadrant operation of the system, and has strong regenerative braking capability. The cost is lower than the inverter control system for AC three-phase induction motors. ② Controller The controller is composed of microprocessors, digital logic circuits and other components. According to the command input by the driver, the microprocessor analyzes and processes the motor rotor position fed back by the position detector and current detector, and makes a decision in an instant, and issues a series of execution commands to control the switched reluctance motor Adapt to the operation of electric vehicles under different conditions. The performance of the controller and the flexibility of adjustment depend on the performance coordination relationship between the software and hardware of the microprocessor. ③ Position detector The switched reluctance motor needs a high-precision position detector to provide the control system with the position, speed and current change signals of the motor rotor, and requires a higher switching frequency to reduce the noise of the switched reluctance motor.　  

5. Application of DC motors in new energy vehicles

  DC motors can be divided into permanent magnet DC motors and winding excitation motors. Generally, the former is used for low power, and the latter is used for high power. The latter is mainly discussed below. 

(1) Brief introduction of DC motor DC motor: a rotating electrical machine that converts DC electrical energy into mechanical energy (DC motor) or converts mechanical energy into DC electrical energy (DC generator). The structure of the DC motor should be composed of two parts, the stator and the rotor. The stationary part of the DC motor is called the stator. The main function of the stator is to generate a magnetic field. It consists of a base, a main magnetic pole, a commutation pole, an end cover, a bearing and a brush device. The part that rotates during operation is called the rotor. Its main function is to generate electromagnetic torque and induced electromotive force. It is the hub for energy conversion of the DC motor, so it is usually called the armature. directional device and fan etc. Brushed DC motors are widely used in occasions that require adjustable speed, good speed regulation performance, and frequent starting, braking and reversing. 

(2) Characteristics of DC motors DC motors have the following advantages: simple structure; excellent electromagnetic torque control characteristics, which can achieve constant torque below the base speed and constant power above the base speed, and can meet the needs of automobiles for low-speed and high-speed rotation of the power source. Torque, high speed and low torque requirements; frequent rapid start, braking and reverse; smooth, stepless, precise, convenient, wide range; strong anti-overload ability, able to withstand frequent impact loads; simple control method, It only needs to be controlled by voltage, and does not need to detect the magnetic pole position. However, it also has the following disadvantages: it is equipped with brushes and commutators, and electric sparks are easily generated on the surface of the commutator during high-speed and heavy-load operation. At the same time, it is difficult to maintain the commutator, and it is difficult to develop to large capacity and high speed. It will generate electromagnetic interference; it is not suitable for use in dusty, humid, flammable and explosive environments; the price is high, and the volume and quality are large. Among them, the electromagnetic interference generated by electric sparks will be fatal to highly electronic electric vehicles. With the development of electronic force technology and control theory, compared with other drive systems, the application of DC motors in electric vehicles has been at a disadvantage and has been gradually eliminated.

  (3) DC motor control system The DC motor control system is mainly composed of a chopper and a central controller. According to the output torque of the DC motor, the input voltage and current of the motor are controlled by the chopper to control and drive the DC motor. motor operation.

  6. Comparison of various motors

Let us first compare the development history of various motors. From Figure 4, we can see that brushed DC motors, general synchronous motors, induction motors and brushed magnet motors have the longest history of commercialization, and their products are constantly being updated. in application. The surface permanent magnet synchronous motors that have been commercialized since the 1980s and the switched reluctance motors, built-in permanent magnet synchronous motors and the latest synchronous reluctance motors developed since the 1990s have entered the market one after another, and have been used in electric vehicles and get applied on hybrid vehicles.　

Figure 4: Comparison of the development history of various motors Based on the current development level, the basic performance comparison of various drive motors is as follows:

Figure 5: Comparison of basic performance of various drive motors

Figure 6: Comparison of the basic performance of various drive motors and then compare which new energy vehicles are widely used in various motors. Asynchronous motors are mainly used in pure electric vehicles, permanent magnet synchronous motors are mainly used in hybrid vehicles, and switched reluctance motors are currently mainly used in passenger cars. From the perspective of the application of different types of new energy vehicle drive motors in China, at present, AC asynchronous induction motors and switched reluctance motors are mainly used in new energy commercial vehicles, especially new energy buses, and the actual assembly and application of switched reluctance motors is less; Permanent magnet synchronous motors are mainly used in new energy passenger vehicles. 

Finally, compare the development status of various motors in my country:

(1) AC asynchronous motor drive system my country has established a development platform for asynchronous motor drive systems with independent intellectual property rights, forming a development, manufacturing, testing and service system for small batch production; product performance basically meets the needs of complete vehicles, high-power asynchronous The motor system has been widely used in various electric buses; through demonstration operation and small-scale market application, product reliability has been initially verified.

  (2) The switched reluctance motor drive system has formed optimized design and independent research and development capabilities. Through reasonable design of the motor structure and improved control technology, the product performance basically meets the needs of the entire vehicle; some companies have an annual production capacity of 2,000 sets. To meet the needs of small batches, some products have been equipped with complete vehicles for demonstration operation, and the effect is good. 

(3) Brushless DC motor drive system Domestic enterprises have effectively improved the performance of brushless DC motor products through reasonable design and improved control technology, basically meeting the needs of electric vehicles; they have initially possessed the design capability of mechatronics.

  (4) The permanent magnet synchronous motor drive system has formed a certain research and development and production capacity, and has developed different series of products, which can be applied to various electric vehicles; some technical indicators of the products are close to the international advanced level, but the overall level is still comparable to that of foreign countries. gap; basically have the integrated design capability of permanent magnet synchronous motors; most companies are still in small-scale trial production, and a few companies have invested in the establishment of special production lines for vehicle drive motor systems.

  (5) Permanent magnet motor materials The main materials of permanent magnet motors are NdFeB magnets, silicon steel and so on. Some companies have mastered the overall magnetization technology of motor rotor magnets assembled first and then magnetized. The highest working temperature of NdFeB permanent magnets developed in China can reach 280°C, but there is still a big gap between the technical level and that of Germany and Japan. Silicon steel is an important magnetic material for the manufacture of motor iron cores. Its cost accounts for about 20% of the motor body, and its thickness has a great impact on iron consumption. Japan has produced 0.27mm silicon steel sheets for automotive motors, and my country has only developed 0.35mm mm silicon steel sheet. 

7. Prospects for the future of drive motors for new energy vehicles

The current development direction of new energy vehicle drive motors has the following aspects: small size and light weight; high efficiency; better torque characteristics; long service life, high reliability; low noise; low price. As time goes by, the development of new energy drive motors presents the following trends:　  

①Permanent magnetization of the motor body: Permanent magnet motors have the advantages of high torque density, high power density, high efficiency, and high reliability. my country has the most abundant rare earth resources in the world, so high-performance permanent magnet motors are an important development direction for vehicle drive motors in my country.

  ②Digitalization of motor control: The emergence of dedicated chips and digital signal processors has promoted the digitization of motor controllers, improved the control accuracy of the motor system, and effectively reduced the system volume.

  ③Electric motor system integration: Through electromechanical integration (motor and engine integration or motor and gearbox integration) and controller integration, it is beneficial to reduce the weight and volume of the drive system, which can effectively reduce system manufacturing costs. Let's talk about a variety of future motors. With the rapid development of new energy vehicle drive technology, many new structures or new concept motors have been put into research. Among them, the new permanent magnet brushless motor is one of the most promising motors at present, including hybrid excitation type, hub type, double stator type, memory type and magnetic gear compound type. In addition, amorphous motors have also begun to enter the field of new energy vehicles. As a new generation of high-performance motors, their own advantages will definitely play a huge role in promoting the development of the new energy vehicle industry. 

(1) Hybrid excitation motor The hybrid excitation motor is to change the topological structure of the motor under the premise of maintaining a high efficiency of the motor, and the main magnetic field of the motor is jointly generated by two excitation sources, so as to realize the adjustment and control of the main magnetic field of the motor and improve the speed regulation of the motor , drive performance or voltage regulation characteristics of a new type of motor. It not only inherits many characteristics of permanent magnet motor, but also has the advantages of smooth and adjustable air gap magnetic field of electric excitation motor. Such as permanent magnet switched reluctance motor and permanent magnet synchronous reluctance motor. (2) Double-stator permanent magnet motor The double-stator motor is a new type of permanent magnet brushless motor that increases the number of stators on the basis of the same volume of the existing motor, so that the number of air gaps changes from one layer to two or more layers. motor. Due to the superposition of torque, the electromagnetic torque acting on the rotor will also increase accordingly, thereby improving the overall torque density and power density of the motor. Due to the high mechanical integration of this kind of motor, it has the characteristics of fast response, good dynamic characteristics, high utilization rate of structural materials and flexible driving.

  (3) Memory motor The memory motor is also called the flux controllable permanent magnet motor. The difference from the general permanent magnet motor is that the magnetization degree of the permanent magnet material itself can be changed in a short period of time by applying magnetization or demagnetization electromotive force. be changed, and its magnetization degree can also be retained after magnetization and demagnetization. Therefore, it has a wider speed range and can avoid additional excitation loss. It is essentially a new simple and efficient field weakening control technology. 

(4) Magnetic gear permanent magnet brushless composite motor This motor is a composite motor integrating a brushless DC drive motor and a coaxial magnetic gear. The so-called coaxial magnetic gear is a high-performance, non-contact variable speed transmission device based on the principle of magnetic modulation harmonics. This kind of motor skillfully utilizes the hollow part of the inner rotor of the coaxial magnetic gear, embeds the motor stator in it, and directly rivets the tire on the outer rotor of the gear, realizing the integration of the motor, magnetic gear and tire, and effectively improving the Space utilization.

  (5) Amorphous motor

Amorphous motor is a new motor with high efficiency, energy saving and no pollution, which uses amorphous alloy instead of traditional silicon steel sheet as core material. It has extremely low loss at high frequency and high efficiency; compared with ordinary motors of the same standard, its volume and mass are greatly reduced, which greatly improves the utilization rate of energy and resources. For the same new energy vehicle, if the use of amorphous motors can increase its mileage by more than 30%, and under the same mileage, the battery can save 30% of the cost. In short, amorphous motors will become the next generation of high-efficiency motors to replace traditional motors due to their advantages such as high efficiency and high power density.