Brushless DC motor is developed on the basis of brush DC motor, which is a kind of high-tech product integrating motor and electronics, and not only has the advantages of small volume, light weight, high efficiency, high control precision, but also retains the excellent mechanical characteristics of ordinary DC motor.
1. Composition of brushless DC motor
Brushless DC motor is similar to brush DC motor, which has rotating magnetic field and fixed electric drive. In this way, the power switching devices in the electronic phase-changing line, such as thyristors, transistors, etc., can be directly connected to the electric drive winding. Inside the motor, there is a rotor position sensor to detect the position of the rotor during operation, which, together with the electronic phase-changing line, replaces the mechanical phase-changing device of the brush DC motor. In summary, the brushless DC motor consists of three main parts: the motor body, the rotor position sensor and the electronic phase-changing circuit.
2. Motor body
The motor body is similar to permanent magnet motor in structure, but without cage winding and other starting devices.
3. Rotor position sensor
The rotor position sensor plays the role of determining the rotor pole position in the brushless DC motor, providing correct phase change information for the logic switching circuit, i.e. converting the position signal of the rotor magnet steel pole into an electric signal, and then controlling the phase change of the stator winding.
4. Electronic phase change circuit
When the stator winding of a phase of the power, the current and the rotor permanent magnet poles produced by the magnetic field interaction and generate torque, drive the rotor rotation, and then by the position sensor rotor magnet position into an electrical signal to control the electronic switching line, so that the stator windings according to a certain order of conduction, stator phase current with the rotor position changes according to a certain order of phase change. As the electronic switching line is synchronized with the rotor angle of the conduction order, thus playing a mechanical commutator commutation role.
5. Basic working principle
Brushless DC motor in order to realize the brushless phase change, first of all require half of the DC motor electric drive winding on the stator, the permanent magnet steel on the rotor, which is just the opposite of the structure of the traditional DC permanent magnet motor, so the brushless DC motor in addition to the stator and rotor composed of the body of the motor, but also by the position sensors, control circuits, and tool logic switches together with the composition of the phase change device, so that the DC brushless motor The magnetic field generated by the stator windings during operation and the permanent magnetic field generated by the rotor magnets during rotation.
