Brushed DC Motor vs. Brushless DC Motor

Brushed DC motor

The main structure of the brushed motor constitutes of the stator plus rotor plus brush. The driving torque is obtained through the rotating magnetic field to output the kinetic energy. The brush and the commutator constantly have contact with each other for friction, and play the role of conduction and phase shift in the rotation process.
The brushed DC motor relies on the contact phase conversion between the carbon brush and the rotor to change the magnetic pole of the winding coil. Therefore, when the phase is suddenly changed, the spark will be generated. Besides, the long-term friction between the carbon brush and the rotator can consume the carbon brush, and the service life of the electric motor will be shortened.
Apart from changing the electric brush, the brushed DC motor should also change peripheral accessories, such as the rotating gear, upon maintenance. This will not only increase the cost, but also partially impair the performance of the whole machine. Therefore, the brush electric motor is just suitable to occasions which do not have a high requirement of the electric motor.
The brush DC electric motor is cheap and easy to control. Under the rated voltage, we just need to regulate the electric current to achieve the purpose of controlling the rotating speed. However, when the brush electric is launched, the torque is not large and can be easily blocked under occasions with a large friction.
When the electric motor is working, the magnetic iron and carbon steel remain motionless despite of mechanical direction swift, rotation of the coil and commutator. The alternating changes of the coil current come along with the commutator of the electric motor's rotation. Through cutting of the magnetic line, the electric field is generated. With the rotation of the electric motor, the coil receives two-level electrification at different moments, which will then generate the magnetic field. After the N-S pole of the magnetic field and the N-S pole of the magnetic iron generated by the coil find a suitable angular difference, the same magnetic poles repel against each other while the different magnetic poles attract each other on the magnetic field, which will then drive rotation of the brushed DC motor.

Brushless DC Motor

The brushless DC motor adopts electronic commutation, with the coil remaining motionless and the magnetic poles rotating. The position of the magnetic poles of the permanent magnet is perceived by Hall elements. According to the perception, the electronic circuits are adopted, and the current direction in the coil is changed at an opportune time, which can ensure generation of the magnetic force in the correct direction to drive the electric motor. This is an effective way to address defects existing in brushed motors.
The brushless DC motor operates at a slow speed but at a high power. The most striking advantage of the brushless DC electric motor, compared with the ordinary electric motor, is that the former can normally operate at a slow speed but a higher power. The brushless DC electric motor has, on the one hand, inherited the advantages of the traditional DC electric current. On the other hand, the carbon brush and slip ring structure are cancelled. Thereby, the machine can operate at a slow speed but at a large power. This can avoid the large load caused by direct driving by the reduction gear. Since the electric motor itself does not have the carbon brush and the excitation consumption, the multi-scale deceleration energy consumption can be eliminated. The electric machine can also realize step-less speed control with a wide range of speed regulation. Additionally, its overload capacity is stronger.
The brushless DC motor adopts soft start and soft stop, and possesses good manufacturability. With better braking, starting and stopping will not arouse vibration of the brushless DC motor. It is one of the major operation characteristics of the brushless DC motor. When the user starts the motor, the machine is started and stopped not via the original electromagnetic braking device or mechanical braking but through the soft start and soft start. Therefore, the machine is highly resistance to vibration and bulging in the operation process. Meanwhile, the machine is not noisy during its operation, and outperforms ordinary electric motors in terms of the operation smoothness, stability of stop and start, and manufacturability.
Maintenance is easy for the brushless DC motor. Easy maintenance is one of the striking characteristics of the brushless DC motor. Since the BLDC motor is small in volume and light in weight, it is thus easier for maintenance. During the daily operation, personnel can prevent the machine from all kinds of faults through daily maintenance, thus effectively extending the life span of the machine.