Working Principle and Difference Between Brushless
Motor and Brushed Motor
Brushless motor: Brushless DC motor consists of motor body and driver, and is a typical mechatronics product. Since brushless DC motor operates in an automatic control mode, it does not need additional starting winding on the rotor like synchronous motor that starts under heavy load under variable frequency speed regulation, nor does it produce oscillation and loss of step when the load changes suddenly. The permanent magnets of small and medium-capacity brushless DC motors now mostly use rare earth neodymium iron boron (Nd-Fe-B) materials with high magnetic energy level. Therefore, the volume of rare earth permanent magnet brushless motor is one frame size smaller than that of three-phase asynchronous motors of the same capacity.
Brushed motor: Brushed motor is a rotating motor that contains a brush device to convert electrical energy into mechanical energy (motor) or mechanical energy into electrical energy (generator). Different from brushless motors, brush devices are used to introduce or extract voltage and current. Brushed motor is the basis of all motors. It has the characteristics of fast starting, timely braking, smooth speed regulation over a wide range, and relatively simple control circuit.
Working principle of brushed motor:
Brushed motor is the first type of motor that everyone comes into contact with. It is also used as a model to introduce electric motors in physics classes in middle school. The main structure of brushed motor is stator + rotor + brush, which obtains torque through rotating magnetic field and outputs kinetic energy. The brush and commutator are in constant contact and friction, which plays a role in conduction and phase change during rotation.
Brushed motor uses mechanical commutation, the magnetic pole is stationary, and the coil rotates. When the motor is working, the coil and commutator rotate, the magnet and carbon brush do not rotate, and the alternating change of the coil current direction is completed by the commutator and brush that rotate with the motor.
In brushed motor, this process is to arrange the two power input ends of each group of coils in a ring in sequence, separate them with insulating materials, form a cylinder-like thing, and connect them to the motor shaft. The power supply passes through two small pillars made of carbon elements (carbon brushes). Under the action of spring pressure, it presses two points on the ring-shaped cylinder where the power supply input of the coil is above from two specific fixed positions to energize a group of coils.
As the motor rotates, different coils or different poles of the same coil are energized at different times, so that the N-S pole of the coil generating the magnetic field has a suitable angle difference with the N-S pole of the nearest permanent magnet stator. The magnetic fields attract each other and repel each other, generating force to drive the motor to rotate. The carbon electrode slides on the coil terminal, like a brush brushing on the surface of an object, so it is called a carbon "brush".
Sliding against each other will rub the carbon brush, causing loss, and the carbon brush needs to be replaced regularly; the carbon brush and the coil terminal are switched on and off alternately, sparks will occur, electromagnetic damage will be generated, and electronic equipment will be interfered.
Working principle of brushless motor.
In brushless motor, the phase change work is handed over to the control circuit in the controller (generally Hall sensor + controller, more advanced technology is magnetic encoder) to complete.
Brushless motor adopts electronic commutation, the coil does not move, and the magnetic pole rotates. Brushless motor uses a set of electronic equipment to sense the position of the permanent magnet pole through the Hall element. Based on this perception, the electronic circuit is used to switch the direction of the current in the coil in time to ensure the generation of magnetic force in the correct direction to drive the motor. The shortcomings of brushless motor are eliminated.
These circuits are motor controllers. The controller of the brushless motor can also realize some functions that the brushless motor cannot realize, such as adjusting the power switching angle, braking the motor, reversing the motor, locking the motor, and using the brake signal to stop the power supply to the motor. Now the electronic alarm lock of the battery car makes full use of these functions.
The brushless DC motor consists of the motor body and the driver, and is a typical mechatronics product. Since the brushless DC motor is operated in an automatic control mode, it will not add a starting winding on the rotor like the synchronous motor that starts under heavy load under variable frequency speed regulation, nor will it produce oscillation and loss of step when the load changes suddenly.
