First, the meaning of the brushless dc motor
there are growing concerns on the environment and energy, to promote the development of electric vehicles and accelerated the competition of the world's great powers in the field of electric vehicles. Under the current battery technology restricted, how to improve the energy efficiency, improve the electric car trip, is the focus of the electric car industry. Big start torque brushless dc motor, speed control performance is good, high efficiency, energy density, strong overload capacity, stable performance, safe and reliable, is the ideal of electric vehicle drive motor. The industrialization production of brushless dc motor, to improve the performance of electric vehicle, and accelerating the development of the electric car industry, the electric car industry in our country to catch up with the world advanced level has a positive role in promoting.
2, advanced
brushless dc motor for electric vehicle is mainly used in urban traffic, vehicle in most of the time the working state of the start, acceleration, braking, therefore starting performance of motor, acceleration, the efficiency of low speed and braking energy regeneration, motor overload capacity, the energy density, the reliability of machine is particularly important for electric vehicles, is one of the important indicators to measure electric vehicle motor. There is currently no optional dedicated motor, electric vehicles can only choose general motor, such as dc series motor, dc shunt motor, permanent magnet dc motor, asynchronous motor, etc. General motor load characteristic of constant load, the electric vehicle features for variable load characteristics, the two features do not match, affect the motor output, then influence the performance of electric vehicles. In addition, the maximum efficiency point of all design in general motor rated point near, when load deviation point, the motor efficiency fell sharply, affected the travel distance of the vehicle. Switched reluctance motor at low speed with large torque, but the efficiency is low, the permanent magnet synchronous motor has high efficiency, but low speed torque cannot ascend. Only the brushless dc motor has all the advantages of the above motor, it has a series dc motor torque at low speed upgrade function, shunt dc motor speed control performance, high efficiency characteristics of permanent magnet synchronous motor and close to the reliability of the asynchronous motor, very suitable for the need of electric vehicles. Technical indicators are in various motor summary in table 1.
all kinds of motor technical indicators summary table 1
sex machine electricity to dc series motor tributary shunt motor permanent magnet dc motor squirrel-cage asynchronous motor switch magnetic resistance motor permanent magnet synchronous motor brushless dc motor starting performance
5 4 4 2, 3, 4, 5
low speed performance of 4 5 4 3, 3, 4, 5
lower efficiency of 3, 3, 4, 3, 4, 5 5 average efficiency
3, 3, 4, 4 and 5 5 energy density 2, 3, 4, 2, 4, 5
overload capacity 4 4 4 5 4 3 5 5
regeneration 3 5
5 4 3 2 2 2 2 5 5 4 4 reliability
the manufacturing cost of 4, 4, 5 4 5 4 4
controller costs 5 5 4 4 4 4
and 36 36 and 37 meter 37 45 to 47
from the table above brushless dc motor is the most ideal electric vehicle drive motor, compared with other motor, its main advantages as follows: (1) motor external characteristic is good, very accord with the load characteristics of electric vehicles especially motor has low speed high torque characteristics of the precious, can provide large starting torque, satisfy the requirement of the vehicle acceleration. (2) the wide speed range, the motor can run at full power in any speed, this is the unique features of brushless dc motor, so that we can save the car mechanical transmission, change the internal combustion vehicle transmission mode, further improve the efficiency of the vehicle. (3) motor with high efficiency, especially under the light load cars, motor can still keep high efficiency, it is very important for precious battery power, this kind of motor is permanent magnet dc motor efficiency more than 10%, higher than that of Y series motor efficiency more than 20%. (4) overload capacity is strong, this kind of motor than Y series motor overload capacity can be improved by more than 20%, can meet the needs of the vehicle bumps blocked. (5) regenerative braking effect is good, because of the permanent magnetic motor rotor has the very high, when the car downhill or brake motor generator can be completely into the state, to recharge the battery. 6. Motor small volume, light weight, high power, can effectively reduce weight, save a space. 7 no mechanical commutator motor, USES the totally enclosed structure, prevent dust from entering the motor internal, high reliability. Simple than asynchronous motor was motor control system.
brushless dc motor is developed on the basis of the permanent magnet synchronous motor, permanent magnet synchronous motor is higher than that in its efficiency and larger torque at low speed, two kinds of external characteristic of the motor as shown in figure 1.
3, the present situation of the brushless dc motor
the motor can be divided into dc motor, synchronous motor and induction motor, the division of three kinds of motor production in China is relatively clear, brushless dc motor is a collection of three kinds of motor, the motor is the development of high-level products, represent the development direction of the machine. The brushless dc motor research has just started, mainly in the institutions of higher learning, such as zhejiang university, Beijing university of aeronautics and astronautics, Shanghai jiaotong university, etc. , are conducted in 1. Under 5 KW prototype studies, tsinghua university is 15 KW motor prototype experiment, the Chinese Academy of Sciences is 28 motor KW prototype experiment. In the enterprise production of high performance, large capacity of this kind of motor manufacturers also have no, only the production of simple structure, low performance, capacity at 0. Under 2 kw, used for electric bicycle motor manufacturers. The international developed countries for the development of brushless dc motor and the same in China, but like the United States, Japan advanced than China in terms of brushless dc motor control.
