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Types And Characteristics Of Electric Vehicle Motors Nov 18, 2019

First, brushed DC motor


The main advantages of brushed DC motors are simple control and mature technology. It has excellent control characteristics unmatched by AC motors. DC motors were used in the early development of electric vehicles, and even now, some electric vehicles still use DC motors to drive them. However, due to the presence of brushes and mechanical commutators, the motor overload capability and speed are further limited, and if it is operated for a long time, it is necessary to frequently maintain and replace the brushes and commutators. In addition, since the loss exists on the rotor, heat dissipation is difficult, which further limits the motor torque quality ratio. In view of the above drawbacks of DC motors, DC motors have not been basically used in newly developed electric vehicles.


Second, AC three-phase induction motor


AC three-phase induction motors are the most widely used motors. The stator and the rotor are made of silicon steel sheets and the sliding rings, commutators and the like are not in contact with each other. Simple structure, reliable operation and durability. The AC induction motor has a wide power coverage and a speed of 12,000 to 15000 r/min. Air cooling or liquid cooling can be used, and the degree of freedom of cooling is high. Adaptable to the environment and able to achieve regenerative feedback braking. Compared with the DC motor of the same power, the efficiency is higher, the quality is reduced by about half, the price is cheap, and the maintenance is convenient.


Third, permanent magnet brushless DC motor


A permanent magnet brushless DC motor is a high performance motor. Its greatest feature is a mechanical contact structure with the external characteristics of a DC motor without a brush. In addition, it uses a permanent magnet rotor with no excitation loss: the heat-generating armature winding is mounted on the outer stator, which is easy to dissipate heat. Therefore, the permanent magnet brushless DC motor has no commutation spark, no radio interference, long life and reliable operation. Easy maintenance. In addition, its speed is not limited by mechanical commutation. If air bearings or magnetic bearings are used, it can run at hundreds of thousands of revolutions per minute. The permanent magnet brushless DC motor system has a higher energy density and higher efficiency, and has a good application prospect in electric vehicles.


Fourth, 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 are no slip rings, windings and permanent magnets on the rotor of the motor, just on the stator. There is a simple concentrated winding, the ends of the windings are short, there is no phase jumper, and maintenance and repair are easy. Therefore, the reliability is good and the rotational speed can reach 15000 r/min. The efficiency can reach 85% to 93%, which is higher than AC induction motor. The loss is mainly in the stator, and the motor is easy to cool; the rotor element permanent magnet has a wide speed range, flexible control, easy to realize various torque-speed characteristics of special requirements, and maintains high efficiency over a wide range. More suitable for electric vehicle dynamic performance requirements.


At present, Tesla is a leading company in the manufacture of electric vehicles. The motors used are three-phase induction motors, while most of the electric vehicle manufacturers use permanent magnet brushless DC motors. The reason is not because of three-phase induction motors. The application in electric vehicles is more advanced than permanent magnet brushless motors, but the asynchronous motor technology used on Tesla has made a major breakthrough. In the past, the biggest drawback of asynchronous motors was that it was difficult to control the rotational speed of the rotor, but with the development of modern semiconductor control technology, this problem has been solved. Tesla made good use of the AC three-phase induction motor with light weight and small size.


Electric vehicles used different motors in different historical periods, and the first to use DC motors with the best control performance and lower cost. With the continuous development of motor technology, mechanical 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.