The brushless DC motor is an electromechanical integrated device that integrates the motor body, controller and rotor position sensor. The working characteristics of the motor are the result of the joint action of each component. To meet the requirements of certain technical indicators, the specific working mode of the brushless DC motor needs to be determined from the perspective of the system, which mainly includes the number of motor phases, winding connection, inverter topology, winding energization, and rotor position detection.
Three-phase DC brushless motors are currently the most widely used. When the inverter adopts the three-phase three-state working mode of the half-bridge structure, it is mostly used for low-power high-speed motors; when the inverter adopts the three-phase six-state working mode of the bridge structure, it can be applied to a variety of drive systems. Because the electromotive force of the winding is non-sinusoidal, which contains a lot of high-order harmonics, the three-phase windings are mostly star-connected. When the size of the motor is not high and the environment is not bad, the position sensor is generally used to detect the rotor position, so that the DC brushless motor has better starting characteristics, anti-overload and impact resistance, and better dynamic characteristics. The brushless DC motor running at a constant speed can be controlled without a position sensor. Since the rotor position sensor is not needed, the size of the motor is reduced and the cost is reduced, but the starting is difficult and the dynamic characteristics are poor.
