Compared with direct current motor and asynchronous motor, the key technology of brushless dc motor is characterized by:
1, the electronic control for dc motor running properties, like better controllability, wide speed range.
2, need rotor position feedback information and electronic polyphase inverter drive.
3, essentially, ac motor, with no spark of brush and commutator, wear problems, it can work in high speed, high reliability can be obtained, long working life, need not often maintenance.
4, high power factor brushless dc motor (BLDCM), the rotor lossless and fever, and have higher efficiency: the data contrast, 7. 5 kw asynchronous motor efficiency is 86. Efficiency of 4%, with the capacity of the brushless dc motor is up to 92. 4%.
5, must have electronic control parts, the total cost is higher than dc motor.
the main motor applied in the communication system are two kinds of induction motor and permanent magnet synchronization motor, according to the working principle of the different type of permanent magnet synchronous motor, can be divided into sine wave back emf of the permanent magnet synchronous motor (永磁同步电动机)And the square wave back emf brushless dc motor (BLDCM), make their drive current due to the different working principle and control method is not the same.
sinusoidal permanent magnet synchronous motor counter electromotive force is one type of sinusoid, to make smooth torque motor, motor winding current flows must also be sinusoidal model, you must know that the continuous rotor position signal, the inverter can provide motor sine voltage or current accordingly, therefore, all-digital fuzzy need to adopt the position of the high resolution encoder or rotating transformer, control algorithm is also more complex.
counter electromotive force is trapezoidal brushless dc motor (BLDCM), as long as the input square-wave motor winding current and torque is straight, therefore, the location of the BLDCM don't need a high resolution sensors, feedback device is simple, the control algorithm is relatively simple. In addition of BLDCM trapezoidal wave air-gap magnetic field is larger than that of all-digital fuzzy sine wave air-gap magnetic field on the utilization of the iron core is higher; And BLDCM is higher than the all-digital fuzzy power density, the output torque per unit volume is bigger. So the application of permanent magnet brushless dc motor and research more extensive attention.
