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Selection of Motor Direct Drive System Parameters


(1) Selection of motor direct drive system parameters

In the energy conversion of pure electric vehicles, the motor is responsible for the conversion of electrical energy to mechanical energy. The electrical energy conversion of the battery is controlled by the motor controller to make the motor in the best working state required by the operation to meet the actual driving conditions of the vehicle. Demand. Therefore, the parameters of the motor directly affect the power and economy of the vehicle. The driving teaching matching of pure electric vehicles is to select the parameters of the motor reasonably on the basis of meeting the requirements of the power performance of the vehicle, reduce costs, and increase driving range. At present, most of the matching of the transmission system of pure electric vehicles is calculated based on the performance indicators of the entire vehicle and the vehicle dynamics equation. In order to obtain higher energy conversion efficiency and make full use of the limited energy sources of pure electric vehicles, the drive motor should be as high as possible in the actual operation. The parameter design of the drive motor mainly includes: peak power, rated power, peak speed, rated speed, peak torque and rated torque.

(2) Performance check of motor direct drive system

Check whether the selection of the motor direct drive system meets the requirements through the highest vehicle speed, continuous gradeability, maximum gradeability, and acceleration performance.

Permanent magnet synchronous motor.

A permanent magnet synchronous motor is a synchronous motor that generates a synchronous rotating magnetic field through permanent magnet excitation. It is mainly composed of three main bodies: the stator, the generator, and the air gap between the stator and the rotor. The permanent magnet acts as a rotor to generate a rotating magnetic field. When the three-phase symmetrical current is applied to the side, the three-phase stator current with a difference of 120 in the spatial position generates a rotating magnetic field in space. The rotating magnetic field of the rotor is moved by the action of electromagnetic force. At this time, the electrical energy is converted into mechanical energy, and the motor output power and rotation Moment.

Permanent magnet synchronous motors have the advantages of high power efficiency, high power factor, low heat generation, simple cooling structure, small size, low noise, maintenance-free, high reliability, and high power density. At present, the drive motors of electric drive products mostly use permanent magnet synchronous motors, which are widely used.

With the rapid development of motor technology, a new type of flat copper wire motor has emerged. The rectangular copper wire motor is a new type of high power density motor, and its rectangular copper wire winding has obvious advantages compared with the traditional round copper wire winding.

2) AC asynchronous motor.

3) Switched reluctance motor.

Definition of Main Parameters of the Motor.

① Motor rated power: also called continuous power, which refers to the specified maximum and long-term working power.

② Peak motor power: The maximum output power allowed by the motor within the specified duration.

③ Motor rated torque: the output torque of the motor at rated power and rated speed.

④ Peak torque of the motor: the maximum torque that the motor is allowed to output within the specified duration.

⑤ Motor speed: the number of revolutions per unit time (per minute), divided into motor rated speed (the lowest speed of the motor under rated power) and the highest working speed (generally the motor speed corresponding to the highest design speed of an electric vehicle).

⑥ Speed ​​control accuracy: the deviation between the actual speed and the expected speed, or the percentage of the actual speed and the expected speed.

⑦Torque control accuracy: the deviation between the actual torque value and the desired torque value, or the deviation between the actual torque value and the desired torque value as a percentage of the desired torque value.

⑧ Speed ​​response time: the time from when the motor controller receives the command message to the first time it reaches the expected value of the specified tolerance range.

⑨Torque response time: the elapsed time from when the motor controller receives the command information to the first time it reaches the expected value of the specified tolerance range.

⑩High-efficiency area: refers to the area enclosed by the contour line formed by a certain efficiency value specified in the Zhao technical document in the efficiency MAP of the motor drive system or the components in the system under the rated voltage.

⑪Torque fluctuation: refers to the output torque fluctuation, peak or

The difference between the maximum value of the trough and the average value in the specified time period.

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