The most basic motor is"DC motor (brushed motor)". A coil is placed in a magnetic field. Through the flowing current, the coil will be repelled by the magnetic pole on one side and attracted by the magnetic pole on the other side. Under this action, it will continue to rotate. The current to the coil is caused to flow in the reverse direction during rotation, causing it to continue to rotate. There is a part called "commutator" in the motor that is powered by "brushes". The position of "brushes" is above the "steering gear" and moves continuously with rotation. By changing the position of the brush, the direction of the current can be changed. The commutator and the brushes are indispensable structures for rotation of the DC motor (FIG. 1).
 

Figure 1: Operation diagram of DC motor (brush motor).
The commutator switches the flow of current in the coil and reverses the direction of the magnetic pole so that it always rotates to the right. The brush supplies power to a commutator that rotates with the shaft.
Features and uses of various types of motorsThe following figure:

Figure 2: Main types of motors
A DC motor (brush motor), which is simple in structure and easy to operate, is generally used for the purpose of "opening and closing of a disc tray" of a home appliance. Or used in automobile "electric rearview mirror opening and closing, direction control" and other purposes. Although it is cheap and can be used in many fields, it also has defects. Because the commutator will contact with the brush, its life is very short, and the brush must be replaced regularly or guaranteed.
The stepper motor rotates with the number of electrical pulses sent to it. The amount of its movement depends on the electrical pulses sent to it, so it is suitable for position adjustment. It is commonly used in households for "paper feeding of fax machines and printers" and the like. Since the paper feeding steps of the fax machine depend on the specifications (engraving, fineness), the stepping motor that rotates with the number of electrical pulses is very convenient to use. It is easy to solve the problem that once the signal stops, the machine will stop temporarily.
Synchronous motors in which the number of revolutions varies with the frequency of the power supply are used for applications such as "rotating tables for microwave ovens. There is a gear reducer in the motor group, which can obtain the number of rotations suitable for heating food. The induction motor is also affected by the frequency of the power supply, but the frequency and the number of revolutions are not consistent. This type of AC motor has previously been used on fans or washing machines.
It can be seen that a wide variety of motors are active in many fields. Among them, BLDC motor (brushless motor) has what kind of characteristics will be so widely used
The "BL" in BLDC motor means "brushless", that is, the "brush" in DC motor (brush motor) is gone. The role of the brush in a DC motor (brushed motor) is to energize the coils in the rotor through the commutator. So how does a BLDC motor without brushes energize the coils in the rotor? The original BLDC motor uses permanent magnets to make the rotor, and there is no coil in the rotor. Since there are no coils in the rotor, there is no need for commutators and brushes for energization. Instead, it is used as a coil for the stator (Figure 3).
In a DC motor (brushed motor), a magnetic field produced by a fixed permanent magnet does not move, and is rotated by a magnetic field generated in a control coil (rotor). To change the number of rotations by changing the voltage. The rotor of the BLDC motor is a permanent magnet that rotates by changing the direction of the magnetic field generated by the surrounding coils. The rotation of the rotor is controlled by controlling the direction and magnitude of the current to the coils.

Figure3: Operation diagram of BLDC motor.
The BLDC motor uses a permanent magnet as a rotor. Since there is no need to energize the rotor, brushes and commutators are not required. The electricity to the coil is controlled from the outside.
There are three coils on the stator of the BLDC motor, each coil has two wires, and there are six lead wires in the motor. In fact, due to the internal wiring, usually only three wires are needed, but there is still one more than the previously mentioned DC motor (brushed motor). Pure by connecting the positive and negative poles of the battery will not move. As for how to run the BLDC motor will be explained in the second part of this series. This time we want to focus on the advantages of BLDC motors.
The first feature of BLDC motors is "high efficiency". It can control its rotation force (torque) to always maintain the maximum value. DC motor (brush motor), the maximum torque in the rotation process can only maintain a moment, can not always maintain the maximum value. If the DC motor (brush motor) wants to get the same torque as the BLDC motor, it can only increase its magnet. This is why small BLDC motors can also emit great power.
The second characteristic is "good control", which is related to the first. BLDC motors can get exactly the torque, number of rotations, etc. you want. The BLDC motor may accurately feed back a target rotation number, torque, etc. Heat generation and power consumption of the motor can be suppressed by precise control. If the battery drive, it can be carefully controlled to extend the drive time.
In addition to durable, low electrical noise and other characteristics. The above two points are the advantages of no brush. The DC motor (brushed motor) will be lost due to the contact between the brush and the commutator for a long time. The parts that touch can also produce sparks. In particular, when the gap of the commutator hits the brush, there will be a huge spark and noise. If you do not want to use the process of noise, will consider the use of BLDC motor