In an environmental environment, electric vehicles have also become a hot spot for research in recent years.Electric vehicles are mainly composed of three parts: motor driver system, battery system, and vehicle control system. The motor drive system is the part of the electrical energy directly into mechanical energy, determining the performance index of electric vehicles.Therefore, it is particularly important for the choice of driving motors.This article will introduce the four driving motors of electric vehicles in detail.
Car motor
Automotive motors generally refer to an electromagnetic device that is transformed or transmitted by electrical energy conversion or transmitting according to the law of electromagnetic induction.The motor is also called a motor and is represented by the letter "M" in the circuit.Its main role is to produce a driving torque as the power source of electric vehicles.
Electric vehicle requirements for driving motors
At present, the evaluation of electric vehicle performance is mainly to consider the following three performance indicators:
(1) Maximum mileage (KM): The maximum mileage of electric vehicles after the battery is fully charged;
(2) Acceleration ability (s): The minimum required from static acceleration from static to a certain speed;
(3) The highest speed (km/h): the highest speed that electric vehicles can reach.
For the motor designed for the driver characteristics of electric vehicles, compared with industrial motors, it has special performance requirements:
(1) Electric vehicle drive motors usually require frequent start/parking, acceleration/deceleration, and torque control of dynamic performance.
(2) In order to reduce the weight of the vehicle, multi-stage transmission is usually canceled. This requires that the motor can provide high torque when low-speed or climbing. Generally speaking
(3) The speed adjustment range is required to be as large as possible, and at the same time, it is necessary to maintain high operating efficiency within the entire speed regulation range;
(4) Try to be designed as a high rated speed when designing the motor. At the same time, the aluminum alloy shell is used as much as possible. The high -speed motor is small in size, which is conducive to reducing the weight of electric vehicles;
(5) Electric vehicles should have the optimized energy use, have the function of braking energy, and the energy of regenerative braking recycling generally reach 10%-20%of the total energy;
(6) The working environment of the motor used by electric vehicles is more complicated and harsh. It is required that the motor has good reliability and environmental adaptability. At the same time, the cost of motor production should not be too high.
Several commonly used drive motors
1. DC motor
In the early days of the development of electric vehicles, most electric vehicles used DC motors as driving motors. This type of motor technology is more mature, easy to control, excellent speed adjustment.EssenceHowever, because the DC motor has a complex mechanical structure, such as: brush and mechanical wiper, which leads to its instantaneous overload capacity and the further improvement of motor speed,Darmament is generated, and maintenance costs are increased.In addition, the sparks from the brush when the motor operates the rotor, waste energy, and difficulty in heat dissipation can also cause high -frequency electromagnetic interference and affect the performance of the vehicle.Due to the above shortcomings of DC motors, the current electric vehicles have basically eliminated DC motors.
2. AC asynchronous motor
AC asynchronous motor is currently a very widely used motor in the industry. It is characterized by fixed and rotor by stacking from silicon steel sheets. Both ends are packaged with aluminum cover., Reliable and durable, convenient maintenance.Compared with the DC motor of the same power, the AC asynchronous motor is more efficient, and the quality is about one -half.If a vector control control method is adopted, the controllability and wider speed regulation range comparable to DC motors can be obtained.Due to the advantages of high efficiency, high power, suitable for high -speed operation, AC asynchronous machines are currently the most widely used motor on high -power electric vehicles.At present, the AC asynchronous motor has been large -scale production, and there are various types of mature products to choose from.However, under high -speed operation, the motors rotor is seriously fever. When working at work, the motor is cooling. At the same time, the driver and control system of the asynchronous motor are complicated.In terms of motors, the efficiency and power density of asynchronous motors are low, which is not good for improving the maximum driving mileage of electric vehicles.
3. permanent magnet motor
The permanent magnet motor can be divided into two types according to the different current waveforms of the stator winding. One is a brushless DC motor, which has a rectangular pulse wave current; the other is the permanent magnet synchronous motor, which has a sine wave current.These two motors are generally the same in structure and working principle. The rotor is permanent magnet, which reduces the loss caused by the inspiration. The winding is installed on the stator to generate torque by AC power, so cooling is relatively easy.Because such motors do not need to install brush and mechanical exchange structure, they will not generate a spark in work. It is safe and reliable, convenient for maintenance, and high energy utilization.
The control system of permanent magnet motor is simpler than the control system of AC asynchronous motor.However, due to the limitation of the technology of permanent magnet materials, the power range of permanent magnet motors is small, and the maximum power is generally only hundreds of millions. This is the biggest disadvantage of permanent magnet motor.At the same time, the permanent magnet material on the rotor will produce a magnetic recession under the conditions of high temperature, vibration and overcurrent. Therefore, under relatively complex working conditions, permanent magnetic motors are prone to damage.And the price of permanent magnet materials is high, so the cost of the entire motor and its control system is high.
4. Switch magnetic motor
As a new type of motor, compared with other types of driver motors, the structure of the switching magnetic resistance motor is the simplest. The fixed and rotor is a dual -convex pole structure made of ordinary silicon steel pieces.Winding, the stator is equipped with a simple concentrated winding, with simple and solid structure, high reliability, light quality, low cost, high efficiency, low temperature, low temperature, easy maintenance and other advantages.And it has good characteristics of the DC speed regulation system, and is suitable for harsh environments, which is very suitable for driving motors for electric vehicles.
Considering that as an electric vehicle -driven motor, DC motors and permanent magnet motors are too poorly adaptable in the structure and facing the complex working environment, and it is easy to cause mechanical and degenerative failures. ThereforeCompared with the machine, it has the following obvious advantages.
4.1 In terms of the structure of the motor body
The structure of the switching magnetic motor motor is simpler than the mouse cage sensor motor. Its prominent advantage is that there is no winding on the rotor, which is just formed by the ordinary silicon steel sheet.The loss of the entire motor is mostly concentrated on the stator winding, which makes the motors simple manufacturing, good insulation, easy to cool, and has excellent heat dissipation characteristics. This motor structure can reduce the volume and weight of the motor.Larger output power.Because the motor rotor has good mechanical elasticity, the switching magnetic resistance motor can be used for ultra -high -speed operation.
4.2 Motor -driven circuit
The phase current of the switch magnetic resistance motor drive system is one -way, and it has nothing to do with the direction of the torque. You can use only one main switch device to meet the four elephant limit running status of the motor.The inspirational winding of the power converter circuit and the motor is directly connected, and the phase circuit is powered independently. Even if a phase winding or controller of the motor fails, the phase can be stopped to work, which will not cause a greater impact.Therefore, both motor and power converters are very safe and reliable, so it is more suitable for harsh environments than asynchronous machines.
4.3 In terms of performance of motor system
There are many control parameters of the switch magnetic resistance motor. It is easy to meet the requirements of the four -quadrant operation of electric vehicles through appropriate control strategies and system design, and can also maintain excellent braking capabilities in high -speed operation areas.The switching magnetic resistance motor is not only efficient, but also maintains high efficiency within a wide range of speed regulation. This is difficult to comparable to other types of motor drive systems.This performance is very suitable for the operation of electric vehicles, which is very conducive to improving the range of electric vehicles.

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