Revising the manuscript acceptance period: 2003-05-08 The coexistence of mankind and the environment and the sustainable development of the global economy have made people eager to seek a means of transportation with low emissions and effective use of resources. The use of electric vehicles is undoubtedly a great achievement. The desired program. Modern electric vehicles are integrated high-tech products such as electric power, electronics, mechanical control, materials science, and chemical technology. The overall operating performance, economy, etc. depends first on the battery system and the motor drive control system. The motor drive system of an electric vehicle generally consists of four main parts, namely a controller, a power converter, a motor, and a sensor. At present, electric motors used in electric vehicles generally include DC motors, induction motors, switched reluctance motors, and permanent magnet brushless motors. Motors for electric vehicles should have high efficiency throughout the entire operating range to increase the driving range of one charge. In addition also requires electric motor motor reliability, able to work in harsh environments, long-term work, the structure is simple to adapt to mass production and operation, low sound, easy to use and maintenance, low price, etc. -21.2 electric motor type and Control methods The main advantages of a DC motor brushed DC motor are its simple control and mature technology. With excellent control characteristics unmatched by AC motors. In the early development of electric vehicles, DC motors were often used. Even now, some electric vehicles still use DC motors to drive them. However, due to the presence of brushes and mechanical commutators, it not only limits the further increase of the motor overload capacity and speed, but also requires frequent maintenance and replacement of brushes and commutators if it is operated for a long time. In addition, because the loss exists on the rotor, heat dissipation is difficult, and the torque mass ratio of the motor is further limited. In view of the above drawbacks of the DC motor, the DC motor 123 has not been basically adopted in the newly developed electric vehicle. 2.2 AC three-phase induction motor AC three-phase induction motor basic performance AC three-phase induction motor is the most widely used motor. The stator and rotor are made of laminated silicon steel plates. There are no sliding rings, commutators, etc., between the rotor and the stator. Simple structure, reliable operation and durability. The power coverage of the AC induction motor is very competitive. The speed can reach 12 000~15000r/min. Air cooling or liquid cooling can be used, and the cooling degree of freedom is high. The adaptability to the environment is good, and it can realize regenerative feedback braking. Compared with the same power DC motor, the efficiency is higher, the quality is reduced by about half, the price is low, and the maintenance is convenient. 2.2.2 AC induction motor control system Since the AC three-phase induction motor cannot directly use the direct current supplied by the battery, the AC three-phase induction motor has a nonlinear output characteristic. Therefore, in an electric vehicle using an AC three-phase induction motor, a power semiconductor device in an inverter needs to be applied, and the DC power is converted into alternating current with adjustable frequency and amplitude to realize control of the three-phase AC motor. The main v/f control method, slip frequency control method. The vector control method is used to harmonically control the frequency of AC excitation of the AC three-phase induction motor and the input voltage of the AC three-phase induction motor to control the magnetic flux and torque of the rotating magnetic field of the AC three-phase induction motor and realize the change of AC three-phase. Induction motor speed and output torque to meet the requirements of the load change characteristics, and can achieve the highest efficiency, making AC three-phase induction motor can be widely used in electric vehicles. 2.2.3 Insufficient AC three-phase induction motor AC three-phase induction motor consumes more power and the rotor is prone to heat. In high-speed operation, it is necessary to ensure cooling of the AC three-phase induction motor, otherwise it will damage the motor. The AC three-phase induction motor has a low power factor, so that the input power factor of the variable frequency transformer device is also low, so a large-capacity frequency conversion transformer device is needed. The cost of the AC three-phase induction motor control system is much higher than that of the AC three-phase induction motor itself, increasing the cost of the electric vehicle. In addition, AC three-phase induction motors also have poor speed regulation. 2.3 Permanent magnet brushless DC motor Permanent magnet brushless DC motor basic performance Permanent magnet brushless DC motor is a high-performance motor. Its greatest feature is that it has the external characteristics of a DC motor and does not have a mechanical contact structure consisting of a commutator and a brush. In addition, it uses a permanent magnet rotor, no excitation loss; heating armature windings and mounted on the outside of the stator, easy heat dissipation, therefore, permanent magnet brushless DC motor without reversing spark, no radio interference, long life, running Reliable and easy to maintain. In addition, its rotational speed is not limited by mechanical commutation. If air bearings or magnetic bearings are used, it can be operated at several hundred thousand revolutions per minute. Compared with other motor systems, permanent magnet brushless DC motors have higher energy density and higher efficiency, and have a good application prospect in electric vehicles. The Permanent Magnet Brushless DC Motor Control System The typical permanent magnet brushless DC motor is a quasi-decoupled vector control system. Since the permanent magnet can only generate a fixed amplitude magnetic field, the permanent magnet brushless DC motor system is very suitable for operation. In the constant torque region, a current hysteresis control or current feedback SPWM method is generally used. In order to further expand the speed, permanent magnet brushless DC motor can also use weak magnetic control. The essence of weak-weakening control is to advance the phase angle of the phase current and provide a direct-axis demagnetization magnetic force to weaken the flux linkage in the stator winding. The insufficiency of the permanent magnet brushless DC motor The permanent magnet brushless DC motor is affected and limited by the permanent magnetic material technology, so that the permanent magnet brushless DC motor has a small power range and the maximum power is only several tens of dry watts. When the permanent magnetic material is subjected to vibration, high temperature and overload current, its magnetic performance may decrease or demagnetization may occur, which will reduce the performance of the permanent magnet motor. In severe cases, it will also damage the motor. In use, it must be strictly controlled to make it No overload occurs. Permanent magnet brushless DC motor in the constant power mode, complex operation, requires a complex control system, which makes the drive system of permanent magnet brushless DC motor costly. 2.4 Switched reluctance motor basic properties of switched reluctance motor Switched reluctance motor is a new type of motor, the system has many obvious features: its structure is simpler than any other motor, there is no slip in the rotor of the motor Rings, windings, and permanent magnets, etc., have only a simple concentrated winding on the stator, and the ends of the windings are short, there is no inter-phase jumper, and maintenance and repair are easy. Therefore, the reliability is good, and the speed can reach 15000r/min. The efficiency can reach 854~934, which is higher than the AC induction motor. The loss is mainly in the stator, and the motor is easy to cool; the rotor has no permanent magnets and can allow higher temperature rise. Speed ​​control range, control flexibility, easy to achieve a variety of special requirements of the torque - speed characteristics, but also in a very wide range of high efficiency. More suitable for electric vehicle power performance requirements. Switched Reluctance Motor Control System The switched reluctance motor has a high degree of non-linearity. Therefore, its drive system is more complex. Its control system includes power converters, controllers and position detectors. See. The field winding of a switched reluctance motor, regardless of the forward current or the reverse current, has the same torque direction and does not require the current to be periodically commutated. Each phase requires only a small-capacity power switch tube, and the power converter circuit. It is simpler, it does not appear straight-through fault, reliability is good, easy to implement the system's soft start and four-quadrant operation, with strong regenerative braking capability. The cost is lower than the inverter control system of the AC three-phase induction motor. The controller consists of microprocessors, digital logic circuits, and interface circuits. The microprocessor analyzes and processes the position of the rotor of the motor feedbacked by the position detector and the current detector at the same time according to the command input by the driver, and makes an immediate decision to issue a series of execution commands to control the switched reluctance motor. Adapt to electric vehicles operating under different working conditions. The flexibility of the controller performance and flexibility of adjustment depends on the software and hardware performance of the microprocessor. The switched reluctance motor requires a high-precision position detector to provide the control system with a change in the position, speed, and current of the motor rotor, and requires a higher switching frequency to reduce the sound of the switched reluctance motor. 2.4.3 Insufficient Switched Reluctance Motor The control system of the switched reluctance motor is more complicated than that of other motors. 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. . Because the switched reluctance motor is a double salient pole structure, there is inevitably torque ripple, and acoustic noise is the main drawback of the switched reluctance motor. However, studies in recent years have shown that using sound design, manufacturing and control techniques, the SDR motor's sonar can be well suppressed. In addition, because the output torque of the switched reluctance motor fluctuates greatly, the DC current of the power converter fluctuates greatly, so a large filter is required on the DC bus 3 Various drive motors used in the electric vehicle have comparative performance. Different motors were used in different historical periods. The earliest was to use DC motors with the best control performance and lower cost. With the continuous development of motor technology, machinery manufacturing technology, power electronics technology and automatic control technology, AC motors, permanent magnet brushless DC motors and switched reluctance motors have shown superior performance over DC motors. In electric vehicles, these The motor gradually replaced the DC motor. Table 1 compares the basic performance of various motors used in modern electric vehicles. Current AC three-phase induction motors, permanent magnet motors and switched reluctance motors and their control devices, the cost is still relatively high, the formation of a large volume of Health Table 1 modern electric vehicle drive motor basic performance comparison items DC induction permanent magnet brushless switch magnetoresistive Motor DC Motor Motor Power Density Low Medium High High Peak Efficiency/% Load Efficiency/% Speed ​​Range (r/min) Reliability Generally Good Excellent Structural Good Ruggedness Good General Excellent Motor Dimensions Large, Medium, Small Motors Motor cost/control performance is best. Controller cost is low. After the general production, the price of these motor and unit control devices will be rapidly reduced, which will meet the requirements of economic efficiency and reduce the price of electric vehicles. 4 Conclusion Through systematic analysis and comparison, it is considered that the overall performance of the permanent magnet brushless DC motor and the switched reluctance motor exceeds that of other motors, which may be the best choice for current electric vehicles. In addition to the several motors and control technologies discussed in this paper, special motors such as permanent-magnet step motors and transverse flux motors can be used in the drive systems of electric vehicles according to special needs. Potassium Perchlorate,High Purity Potassium Perchlorate,Bulk Potassium Perchlorate,Potassium Perchlorate Powder Rucheng Sanxing Electric Chemical Co.,Ltd , https://www.3xchemical.com