Introduction to DC Motor
1. Structure of DC motor
The motor's structure should consist of two parts: the stator and the rotor. The stator is stationary during operation and generates a magnetic field. The rotor is rotating during operation and generates electromagnetic torque and induced electromotive force. It is the hub of energy conversion for DC motors.
The brushless DC motor mainly comprises a rotor made of permanent magnetic material, a stator with coil windings, and a position sensor.
The main rotor is the rotating part of the motor body and generates the excitation magnetic field. It consists of three parts: permanent magnets, magnetizers, and supporting parts.
Permanent magnets and magnetizers are the core of generating magnetic fields and are composed of permanent magnetic materials and magnetic conductive materials. The following permanent magnetic materials are commonly used in brushless DC motors: aluminum nickel cobalt, ferrite, neodymium iron boron, and rare earth cobalt permanent magnetic materials with high magnetic energy products.
Magnetic conductive materials are generally made of silicon steel, electrical pure iron, or 1J50 Permalloy. As shown in Figures (a) and (b). The first structure is that the tile-shaped magnetic steel is pasted on the outer surface of the rotor core, which is called the salient pole type; the second structure is that the magnetic steel is inserted into the groove of the rotor core, which is called the embedded type or hidden pole type.
2. Working Principle of DC Motor
Working principle of brushless DC motor: As shown in the figure, the DC power supply supplies power to the switch circuit (driver). The driver controls the transistor switch in the driver according to the rotor polarity and speed signal fed back by the position sensor, and provides square wave power to the three-phase winding of the motor stator, thereby driving the rotor to operate.
3. Characteristics of brushless DC motor
It has the advantages of traditional DC motors, and at the same time eliminates the carbon brush and slip ring structure; small size, light weight, large output, suitable for small and medium power motors;
The control is relatively simple, stepless speed regulation, wide speed regulation range, strong overload capacity; high efficiency, high reliability, simple repair and maintenance, low cost, low noise and vibration.
