Semco university – All about the Lithium-Ion Batteries


How EV Motors Drive the Future of New Energy Vehicles

The motor, as the name implies, is an electrical original that converts electrical energy and mechanical energy. When the electrical energy is converted into mechanical energy, the motor shows the working characteristics of the motor. When the mechanical energy is converted into electrical energy, the motor shows the working characteristics of the generator. Combined with the new energy vehicles, when the new energy vehicle drives the vehicle forward or backward in the discharge state, it shows the motor characteristics. When the vehicle loosens the acceleration pedal or steps on the brake pedal, it shows the characteristics of the generator.

Classification of drive motors

At this stage, there are two commonly used drive motors for new energy vehicles, permanent magnet synchronous motors, and AC asynchronous motors, most new energy vehicles use permanent magnet synchronous motors, and only a small number of vehicles use AC asynchronous motors. Both types of motors are AC motors. For low-speed electric vehicles, DC motors are more used. DC motor is also the first motor to be used in electric vehicles. This motor is characterized by good control performance and low cost. However, with the development of electronic technology, mechanical manufacturing technology, and automatic control technology, AC motors have shown better performance than DC motors, so they have gradually replaced DC motors.

Permanent magnet synchronous motor

Combined with various factors, from the perspective of energy conservation, cost, and performance, the permanent magnet synchronous motor will be the absolute main force in the field of passenger vehicles in the future.

(1) Basic structure

The permanent magnet synchronous motor is mainly composed of an end cover, shell, stator, and rotor. The core is the rotor structure embedded or attached to the permanent magnet. The permanent magnet mostly uses a rare earth magnet called neodymium iron boron.

(2) Basic principles

After the stator part of the permanent magnet synchronous motor enters the three-phase alternating current modulated by the inverter, the stator armature generates a space magnetic field, which interacts with the permanent magnet rotor (magnetic pole fixed). Through the principle of homogeneous repulsion and heterosexual mutual attraction, it produces the electromagnetic torque output in the same direction as the stator’s rotating magnetic field, that is, the rotor rotation speed is equal to the speed of rotating the magnetic field is called “synchronization”. When the output torque exceeds the friction torque of the rotor and the damping torque of the permanent magnet, the motor begins to work outward to overcome the rolling resistance, air resistance, acceleration resistance, etc. of the car, and drive the car.

(3) Basic characteristics

A permanent magnet synchronous motor is mainly characterized by energy saving, high power density, high efficiency, small size, and light weight. The main disadvantage is that the rotor structure is relatively complex, the cost is high, there is a risk of high-temperature demagnetization, and it is difficult to control weak magnetism.

AC asynchronous motor

Three-phase AC asynchronous motor is a relatively mature drive motor, also known as an induction motor.

(1) Basic structure

The structure of the AC asynchronous motor is roughly the same as that of the permanent magnet motor. It is also composed of an end cover, a shell, a stator, and a rotor. The difference is the rotor part, which has no permanent magnets, which are mainly divided into a squirrel cage rotor and a winding rotor.

(2) Basic principles

The three-phase stator winding of the asynchronous motor enters AC to generate a rotating magnetic field, which cuts the rotor winding so that the rotor winding generates an induced electromotive force. Because the rotor winding is a closed path, the current is generated in the rotor, and the direction is the same as the induced electromotive force. The rotor conductor carrying the current will generate electromagnetic force under the action of the stator rotation magnetic field. The electromagnetic force generates an electromagnetic torque, which drives the motor shaft to rotate, overcomes the resistance, and then drives the car.

(3) Basic characteristics

The advantages of asynchronous motors mainly include mature control technology, low cost, and relatively simple structure. The disadvantages are excitation loss, large energy consumption, poor low-speed start-up, low efficiency under light load, and insufficient energy saving and efficiency compared with permanent magnet motors.

In summary, under the premise that the country advocates energy conservation, high endurance of new energy vehicles, and lightweight models, the advantages of permanent magnet synchronous motors are far greater than those of AC asynchronous motors. After gradually solving the problems of demagnetization and high-speed control of permanent magnet motors, it will certainly become the core driving system of new energy vehicles.


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