Brushless dc motor is composed of main body of the motor and drive, is a typical mechatronics product. The stator winding of the motor to make more balanced three-phase y connection, with three phase asynchronous motor is very similar. On the rotor of the motor with the magnetization of the permanent magnet has, in order to detect the polarity of the motor rotor, inside the motor is equipped with position sensor. Drive consists of power electronic devices and integrated circuit, its function is: accept the motor start, stop, brake signal, to control the motor start, stop, and the brake; Accept the position sensor signals and positive &negative, used to control the inverter bridge on and off of each power tube produce continuous torque; Accept the speed instruction and speed feedback signal, which is used to control and adjust the speed; To provide protection and display, and so on. Dc motor has a rapid response, large starting torque, rotating speed of from zero to rated speed can provide the rated torque performance, but the advantages of dc motor is also its drawback, because the direct current machine to produce a constant torque under the rated load performance, the armature magnetic field and rotor magnetic field must be constant to maintain °, this is about to borrow from the carbon brush and commutator. Carbon brush and commutator motor rotation would produce sparks, carbon powder, so besides can cause damage of components, its usage is restricted. Ac motor without carbon brush and commutator, free maintenance, strong, wide application, but if you want to achieve the equivalent of dc motor according to the characteristic performance must use complex control technology to achieve. Nowadays the rapid development of the semiconductor component switching power frequency to speed up the many, improve the performance of the drive motor. Microprocessor is also more and more fast, which can realize the two ac motor control on a turning shaft in the rectangular coordinates system, appropriate control of ac motor current component in two axis, similar to dc motor control and the performance of the dc motor is quite. Also has a lot of microprocessor control motor required functionality in the chip, and volume smaller and smaller; Such as analog/digital converter, pulse width modulation. Brushless dc motor which is electrically control ac motor commutation, similar dc motor features and without dc motor institutions lack a kind of application.
