Brushless dc motor is widely applied in many fields and the three types of its applications are in the following. The first is the continuous loading application, which mainly requests steady speed but the speed accuracy is not highly emphasized in this situation.
Examples as pumps, fans, blowers and other application types are with low costs and more for the open-loop control. The second is the application of variable load, which mainly requires the speed change within a certain range and has higher demand of the rotational speed of the motor characteristics and dynamic response time.
Drying machine and compressor in the household appliances and pump control, electric controller and engine control in the automobile industry are very good examples. The cost of the system of this kind of application is relatively higher.
The third is the location application. Most of the industrial control and automation applications fall into this category. Such applications tend to deliver the energy, so dynamic response of the speed,the controller and the torque are specially required.

Brushless DC motor, which is made up of a drive and the electric motor, is a typical electromechanical product. The stator winding of the electric motor is wye connected triphase symmetrically which is very similar with three-phase asynchronous motor.

brushless dc motor

The rotor of the motor is stuck with a permanent magnet which has been magnetized. A position sensor is equipped in the motor in order to detect the polarity of the rotor. The drive is constituted by power electronic devices and integrated circuit. It has four main functions as following. First, a drive receives the signal when the motor starts, stops and brakes in order to control the motor correspondingly.

Second, it receives the position sensor signal and a positive reversal signal to control the switch of the inverter’s each power transistor and produce continuous torque. Third, it receives the speed command and speed feedback signal to control and adjust the speed. Fourth, it provides protection and display space.

Brushless DC motor switches the stator and rotor of an ordinary DC motor. Its rotor produces air gap flux for permanent magnet. And the stator is an armature composed of multiphase winding. Brushless DC motor has similar structure with the permanent magnet synchronous motor.

The stator of a brushless DC motor has the same structure with a synchronous motor or induction motor. After multiple phase winding such as three-phase, four-phase, five-phase winding is embedded into the iron core, the winding can be shaped into a star or triangle, and separately connects with each power tube of the inverter so as to make reasonable commutation.

Rotor is mostly made by samarium,cobalt, neodymium, iron, boron or other rare earth materials with high coercivity and high remanence. The magnetic pole be divided into surface magnetic pole, the embedded pole and the annular magnetic poles due to the different placement of the magnetic materials in the magnetic poles. Because the motor body is a permanent magnet motor, brushless DC motor is also called permanent magnet brushless DC motor.