What is a BLDC motor?

    After the supply of electricity (voltage, current), it is the motor that can carry out mechanical movement. There are various types of motors, and the "BLDC motor" has high efficiency and good operability, can be widely used in a variety of purposes, and look forward to the low power consumption it brings.

An electric motor is a device for obtaining energy
    When engineers want to use electrical and electronic machines to do something in the real world, they will think about how to turn electrical signals into "forces". What converts the electrical signal is the actuator, that is, the motor. The motor can be regarded as "the element of force that converts electricity into machinery".
    The most basic motor is the "DC motor (brush motor)". By placing a coil in a magnetic field, the coil is repelled by the magnetic pole on one side and attracted by the magnetic pole on the other side, rotating constantly under this effect. In the process of rotation, the current to the coil is reversed, so that it continues to rotate. A part of the motor called the "commutator" is powered by the "brush", the "brush" is located above the "steering", and constantly moves with the rotation. By changing the position of the brush, the direction of the current can be changed. The commutator and brush are integral to the rotation of a DC motor (Figure 1).

    We classify the motors according to the type of power supply and the principle of rotation (Figure 2). Let's take a brief look at the characteristics and uses of various types of motors.

    The DC motor (brush motor) with simple structure and easy operation is usually used in the "opening and closing of the disc tray" of household appliances. Or used in the car's "electric rear-view mirror opening and closing, direction control" and other purposes. Although it is cheap and can be used in many fields, it also has drawbacks. Because the commutator will be in 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 at it. Its movement depends on the number of electrical pulses sent to it, so it is suitable for position adjustment. In the home is usually used for "fax machine and printer paper feed" and so on. Since the paper feed step of the fax machine depends on the specification (engraving, fineness), the stepper motor that rotates with the number of electrical pulses is very easy to use. It is easy to solve the problem that the machine will temporarily stop once the signal is stopped.
    Synchronous motors in which the number of rotations varies with the frequency of the power supply are used for such purposes as "rotating tables for microwave ovens". There is a gear reducer in the electric unit to get the number of rotations suitable for heating food. Induction motors are also affected by the frequency of the power supply, but the frequency and rotation number are not consistent. Previously this type of AC motor was used in fans or washing machines.
    It can be seen that a wide variety of motors are active in many fields. Among them, what are the characteristics of the BLDC motor (brushless motor) that will be so widely used?

How does the BLDC motor rotate
    The "BL" in the BLDC motor means "brushless", that is, the "brush" in the DC motor (brushed motor) is gone. The role of the brush in a DC motor (brushed motor) is to energize the coil in the rotor through the commutator. So how does a BLDC motor without a brush transmit electricity to the coil in the rotor? The original BLDC motor motor uses a permanent magnet to do the rotor, the rotor is no coil. Since there are no coils in the rotor, commutators and brushes for electrification are not required. Instead, a coil is used as the stator (Figure 3).

    The magnetic field created by the fixed permanent magnet in the DC motor (brush motor) is not moved, and is rotated by the magnetic field generated by the control coil (rotor) in its interior. You change the number of rotations by changing the voltage. The rotor of a BLDC motor is a permanent magnet that rotates by changing the direction of the magnetic field generated by the surrounding coil. The rotation of the rotor is controlled by controlling the direction and magnitude of the current to the coil.

Advantages of BLDC motor
    The stator of the BLDC motor has three coils, each coil has two wires, and the motor has a total of six lead wires. In fact, because it is an internal connection, usually only three wires are needed, but it is still one more than the DC motor (brush motor) previously said. Just by connecting the positive and negative terminals of the battery, it won't move. How to run the BLDC motor will be explained in the second installment of this series. This time we want to focus on the advantages of BLDC motors.
    The first feature of BLDC motors is "high efficiency". Its turning force (torque) can be controlled to always maintain a maximum. DC motor (brush motor), the maximum torque during rotation can only be maintained for a moment, can not always maintain the maximum. 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 even small BLDC motors can emit powerful forces.
    The second characteristic is "good control", which is related to the first. BLDC motors can get exactly the torque, rotation number, and so on you want. BLDC motor can accurately feedback the target rotation number, torque, etc. The heat and power consumption of the motor can be suppressed by precise control. If it is battery driven, it can extend the driving time through careful control.
    In addition to durable, low electrical noise and other features. The above two points are the advantages brought by brushless. DC motor (brush motor) due to the contact between the brush and the commutator, long-term use will have loss. The touching parts also produce sparks. Especially when the gap of the commutator hits the brush, there will be a huge spark and noise. If you do not want to produce noise during use, you will consider using BLDC motors.

BLDC motors are suitable for these purposes
    Where are BLDC motors generally used for high efficiency, diverse control and long life? It is often used in products that can play their characteristics of high efficiency and long life and be used continuously. For example: home appliances. People began to use washing machines and air conditioners very early. Recently, BLDC motors have also begun to be used in electric fans, and they have successfully promoted a significant reduction in power consumption. It is because of the high efficiency that the consumption of electricity goes down.
    The BLDC motor is also used in the vacuum cleaner. In one case, a significant increase in the number of rotations was achieved through a change control system. This example demonstrates the good control of BLDC motors.
    As an important storage medium, the hard disk also uses BLDC motors for its rotating part. Because it is a motor that needs to run for a long time, durability is important. Of course, it is also used to curb power consumption. High efficiency here is also related to low consumption of electricity.

There are many more uses for BLDC motors
    BLDC motors are expected to be used in a wider range of fields. BLDC motors will find widespread use in small robots, especially "service robots" that provide services outside of manufacturing. "Positioning is important for robots, shouldn't you use stepper motors that run with the number of electrical pulses?" Some might think so. But in terms of force control, BLDC motors are more suitable. In addition, if a stepper motor is used, a structure such as a robot wrist needs to provide a considerable current to be fixed in a certain position. If the BLDC motor, it can cooperate with the external force to provide only the required power, thus curbing the consumption of power.
    It can also be used in transportation. For a long time, the elderly have mostly used simple DC motors in electric vehicles or golf carts, but recently they have begun to use high-efficiency BLDC motors with good control. The battery life can be extended by subtle control. BLDC motors are also suitable for use in drones. In particular, the multi-axis rack UAV, because it is by changing the rotation number of the propeller to control the flight attitude, so the BLDC motor that can accurately control the rotation is very advantageous.
    How's that？? BLDC motor is a high quality motor with high efficiency, good control and long life. However, to maximize the power of BLDC motors, you need the right control. How do you do it? Let's look forward to the next one.