Comparison of four kinds of electric vehicle drive motor

2017-03-09 motor technology and Application

New energy vehicles with environmental protection, saving, simple three advantages. In pure electric vehicles is particularly evident: the motor to replace the fuel engine, driven by the motor without automatic transmission. Compared with the automatic transmission, the motor has the advantages of simple structure, mature technology and reliable operation, and is even regarded as one of the promising fields of the automobile industry in china.

New energy electric vehicle is mainly composed of three parts of motor drive system, battery system and vehicle control system, the motor drive system is directly convert electrical energy into mechanical energy, determines the performance of electric vehicles. Therefore, the choice of drive motor is particularly important.

Electric vehicle drive motor requirements have the following characteristics:

- wide constant power range, meet the transmission performance of the car

The starting torque and high speed capability

- high efficiency, wide high efficiency area

The instantaneous power, strong overload capacity

The high power density, small volume, light weight

- high adaptability to environment, adapt to the harsh environment

- high energy feedback efficiency

According to the principle of driving, the electric motor drive motor can be divided into the following 4:

1, DC motor

In the early development of electric vehicles, many electric vehicles are the use of DC motor program. The main purpose is to see the DC motor products mature, easy to control, speed characteristics. But because of the short board DC motor itself is very prominent. The mechanical structure of its own complex (mechanical brush and commutator etc.), restrict the further improvement of its instantaneous overload capacity and motor speed; but in the long time work, the mechanical structure of motor will produce loss, increase the cost of maintenance. In addition, the operation of the motor when the spark will spark the rotor heat, waste energy, heat dissipation, but also cause high frequency electromagnetic interference, these factors will affect the specific vehicle performance.

Due to the shortcomings of DC motor is very prominent, the current electric vehicles have been eliminated DC motor.

2, AC asynchronous motor

AC asynchronous motor is a kind of motor is widely used in the current industry, the characteristics of stator and rotor are made of silicon steel laminations, aluminum cover package ends between the stator and the rotor has no contact mechanical parts, simple structure, reliable operation and convenient maintenance. AC asynchronous motor with the same power DC motor efficiency is higher, the quality is about 1/2 light.

If the vector control method is adopted, the controllable and adjustable speed range can be obtained. Because of the advantages of high efficiency, high specific power and suitable for high speed operation, AC asynchronous machine is the most widely used motor.

But the motor rotor at high speed under the condition of serious work to ensure the motor cooling, and asynchronous motor drive and control system of the motor is very complex, the cost is high, the operation also need the inverter to provide reactive power to establish additional magnetic field, and therefore compared to permanent magnet motor and switched reluctance motor asynchronous motor, power density and the efficiency is low, energy efficiency is not the optimal choice.

Asynchronous motors are used in many areas of the United States, which is also man-made and road related. In the United States, the highway has a certain scale, in addition to the big city, car at a high speed continuous running, so the asynchronous motor can make high speed and high efficiency at high speed are widely used.

3, AC asynchronous motor

Permanent magnet motor stator winding current waveform according to the different can be divided into two types, one is the brushless DC motor, it has a rectangular pulse current; the other is a permanent magnet synchronous motor, it has a sinusoidal current.

The two motor is roughly the same as in the structure and working principle, the rotor is a permanent magnet, reducing loss of excitation caused by stator winding are installed by alternating current to generate torque, so the cooling is relatively easy. Because this kind of motor does not need to install the electric brush and the mechanical commutation structure, the work does not have the commutation spark, safe and reliable operation, easy maintenance, high energy utilization.

Compared with the control system of AC induction motor, the control system of permanent magnet motor is simpler. But due to the limitation of permanent magnetic materials, high temperature, vibration and flow conditions, the permanent magnet rotor can generate the demagnetization phenomenon, so the relatively complex work conditions, permanent magnet motor is easy to be damaged, so that a further improvement.

Moreover, the price of the permanent magnetic material is high, so the cost of the whole motor and its control system is high. At present, only the rare earth resources are rich in china. Like Japan, Europe, or the use of light rare earth permanent magnet materials to do permanent magnet motor, or directly to the use of rare earth materials, but the controller design requirements of higher switched reluctance motor.

4, switched reluctance motor

As a new type of motor, switched reluctance motor, compared to other types of driving motor, switched reluctance motor's structure is simple, the stator and the rotor are doubly common silicon steel laminated structure, no winding on the rotor, the stator with concentrated winding is simple, has simple structure, high reliability and quality light weight, low cost, high efficiency, low temperature rise, the advantages of easy maintenance etc.. And it has the excellent characteristics of good controllability of DC speed regulation system,