Brushless DC motor is composed of motor body and driver, which is a typical mechatronics product. The stator winding of the motor is mostly made of three-phase symmetric star connection, which is very similar to the three-phase asynchronous motor. The rotor of the motor is glued with magnetized permanent magnets, and in order to detect the polarity of the motor rotor, a position sensor is installed inside the motor. The driver is composed of power electronics and integrated circuits, and its functions are: to accept the start, stop and brake signals of the motor to control the start, stop and brake of the motor; Accept position sensor signals and forward and reverse signals, which are used to control the on-off of each power tube of the inverter bridge to generate continuous torque; Accept speed command and speed feedback signal to control and adjust the speed; Provides protection and display, and more.
DC motor has fast response, large starting torque, from zero speed to rated speed has the performance of providing rated torque, but the advantage of DC motor is also its disadvantage, because DC motor to produce the performance of constant torque under rated load, the armature magnetic field and rotor magnetic field must be maintained at 90°, which is through carbon brushes and commutators. Carbon brushes and commutators generate sparks and toner when the motor rotates, so in addition to causing damage to components, the use of them is also limited. AC motor has no carbon brush and commutator, maintenance-free, robust, widely used, but in terms of characteristics, it must be achieved with complex control technology to achieve the performance equivalent to DC motor. Today's semiconductors are developing rapidly, and the switching frequency of power components is much faster, improving the performance of drive motors. The speed of the microprocessor is also getting faster and faster, which can realize the AC motor control in a rotating two-axis Cartesian coordinate system, properly control the AC motor in the two-axis current component, and achieve similar DC motor control and have the same performance as the DC motor.
In addition, there are many microprocessors that do the necessary functions to control the motor in the chip, and the volume is getting smaller and smaller; Analog-to-Digital Converter (ADC), Pulse Wide Modulator (PWM)... Wait. Brushless DC motor is an application that electronically controls the commutation of AC motor to obtain similar characteristics of DC motor without the absence of DC motor mechanism.
