来源：http://www.jnmcd.com 发布时间：2020-06-17 浏览：次
Working principle of brush motor
The brush motor is the first type of motor that we contact. It is also used as a model to show the introduction of the motor in the physics class in middle school. The main structure of the brush motor is stator + rotor + brush. The rotating torque is obtained through the rotating magnetic field, thus the kinetic energy is output. The brush and the commutator are in constant contact and friction, and play the role of conducting and commutating in rotation.
The brush motor adopts mechanical commutation, the magnetic pole does not move, and the coil rotates. When the motor works, the coil and commutator rotate, the magnetic steel and carbon brush do not rotate, and the alternating change of coil current direction is completed by the commutator and brush rotating with the motor.
In a brush motor, the process is to arrange two power input ends of each coil into one ring in turn, separate them with insulating materials, and form a cylinder like thing, which is integrated with the motor shaft. The power supply is made of two carbon elements through a small column (carbon brush). Under the action of spring pressure, from two specific fixed positions, the coil power supply is pressed on top Enter two points on the circular cylinder to energize a set of coils.
With the rotation of the motor, the different poles of different coils or the same coil are energized at different times, so that the N-S pole of the coil generating magnetic field has a suitable angle difference with the N-S pole of the nearest permanent magnet stator, and the magnetic field attracts and repels each other in opposite direction, generating force, and promoting the rotation of the electric machine. The carbon electrode slides on the coil connector like a brush on the surface of an object, so it is called a carbon "brush".
Sliding each other will rub the carbon brush and cause loss, so it is necessary to replace the carbon brush regularly; the on-off alternation between the carbon brush and the coil terminal will cause electric sparks, electromagnetic damage and interference with electronic equipment.
Working principle of BLDCM
In the BLDCM, the work of commutation is done by the control circuit in the controller (generally Hall sensor + controller, the more advanced technology is magnetic encoder).
The electric commutation is adopted for the BLDCM, the coil does not move and the pole rotates. The BLDCM uses a set of electronic equipment to sense the position of permanent magnet pole through Hall element. According to this perception, the electronic circuit is used to switch the direction of current in the coil timely to ensure that the magnetic force in the correct direction is generated to drive the motor. The disadvantages of the brush motor are eliminated.
These circuits are motor controllers. The controller of the BLDCM can also realize some functions that the BLDCM can not achieve, such as adjusting the power switch angle, braking the motor, reversing the motor, locking the motor, using the brake signal, stopping the power supply to the motor. Now the electronic alarm lock of battery car makes full use of these functions.
BLDCM is a typical mechatronics product, which is composed of motor body and driver. Because the BLDCM is operated by automatic control, it will not add additional starting winding on the rotor like the synchronous motor started by heavy load under frequency conversion and speed regulation, nor will it produce oscillation and out of step when the load suddenly changes.
The difference of speed regulation between brush motor and non brush motor
In fact, the control of both kinds of motors is voltage regulation. Only because the electronic commutation is adopted in the BLDCM, digital control is needed to realize it. The brush DC is commutation through the carbon brush, and the traditional analog circuits such as SCR can be controlled, which is relatively simple.
1. The speed regulation process of the brush motor is to adjust the voltage of the motor power supply. The adjusted voltage and current are converted through commutator and brush to change the strength of the magnetic field generated by the electrode, so as to change the speed. This process is called variable voltage speed regulation.
2. The speed regulation process of the BLDCM is that the voltage of the power supply of the motor is constant, the control signal of the motor is changed, and the speed is changed by changing the switch speed of the high power MOS transistor through the microprocessor. This process is called frequency control.
Copyright © 2018 济南美磁达电子有限公司 All Rights Reserved