An Introduction to BLDC Motor

Posted on Jan 24, 2021

BLDC Motor

The advantages of brushless direct current electric motors over conventional brushed electric motors include high-speed operation, ideal electronic control, low maintenance and equipment longevity, and also the high power-to-weight ratio. Brushless direct current electric motors can be used in a wide variety of applications such as computer peripheral equipment like disk drives, various power tools, and also applications in the aerospace and automotive industry.

What Is a BLDC Motor?

BLDC motor, which is the acronym of brushless direct current electric motor, is a type of synchronous motor which is powered by direct currents through the switching power supply or inverter which transfer the power from DC to AC form in order to drive every stage in a closed-loop controlling system. The motor is also known as BL motor, electronically commutated motor, EC motor, and synchronous DC motors. Both inverter and switching power supply are power electronic devices that can alter and transmit the direct current electricity to alternating current electricity.
 
BLDC motors provide pulses, which refers to a brief burst of direct current voltage that has an abrupt rise and decay, to the motor windings which regulate the running speed and torque of BLDC motors. Brushless direct current electric motors replaced the design of brushes, or commutators, which were utilized in a variety of conventional electric motors.

The advantages of brushless direct current electric motors over conventional brushed electric motors include high-speed operation, ideal electronic control, low maintenance and equipment longevity, and also the high power-to-weight ratio. Brushless direct current electric motors can be used in a wide variety of applications such as computer peripheral equipment like disk drives, various power tools, and also applications in the aerospace and automotive industry. Last but not least, BLDC motors have the direct drive arrangement that replaced the rubber belts and gearboxes in washing machines today.
 

How Does a BLDC Motor Work?

The vital elements of a BLDC motor are the permanent magnets and the rotating armature inside. The permanent magnets on the outside of the motor’s construction are stationary, and the magnets are also called "stators". On the other hand, the armature is also known as "rotor", spinning and containing an electromagnet. In brushless direct current electric motors, the permanent magnets spin around the fixed rotor, removing the problems with respect to the connection of currents and the moving rotor. BLDC motors are flipped inside out in the cycle, which requires no brushes to alter the electromagnetic field. The computer controller will charge the electromagnets in the stator and spin the armature an entire 360 degrees. 
    
Compared to the structure and working principle of brushless direct current electric motors, in the brushed direct current motor, the armature spins 180 degrees as the current electricity is transferred to the rotor. To allow the rotor to rotate 360 degrees, the poles of the magnet have to flip, and the brushes will make contact with the stator when the armature rotates, altering the magnetic field further. The electronic controlling unit eliminates the need for brushes or commutator assembly in the brushed DC motors and allows the BLDC motor to consistently switch the phase to keep running.

The core elements of brushless direct current electric motors include the permanent magnet, making the construction similar to a PMS motor, which stands for permanent magnet synchronous motor. The structure of BLDC motors is also similar to switched reluctance motors or asynchronous motors. When utilizing a neodymium magnet, BLDC motors can be subdivided into three styles: out-runner, in-runner, or axial. The difference among the three lines in the relationship between the stator and the rotor. In the out-runner style, the rotor surrounds the stator while the rotor is surrounded by stators in the in-runner style; on the other hand, in axial style, the stator and the rotor are parallel to each other in the flat form.
 

Applications of BLDC Motors

Brushless direct current electric motors are preferred for the quiet operation, lighter device body, and much longer lifespans. Thanks to the electrical current control of the computers, BLDC motors can provide high precision motion control. The benefits make BLDC motors widely utilized in modern equipment especially when low noise, low heat production, and consistent running are the requirements of the applications.
 

Motion Control Applications

BLDC motors are widely used as the drives of pumps, motion fans, or spindles in various adjustable speed applications. The brushless DC motors can build high torque with ideal speed response. Moreover, the motors have considerable energy efficiency and also ideal thermal properties. BLDC in motion control applications uses an electronic motor controlling system and rotor position response sensor to receive the speed response. 

BLDC motors are commonly utilized as servo motors in the servo drives of machine tools. Servo motors are the core of high precision positioning, motion control, and other mechanical operations. Although direct-current stepper motors can also be utilized in these kinds of applications, stepper motor works with open-loop control and therefore generally has torque pulsations. In conclusion, brushless direct current electric motors are more ideal to serve as the servo motor due to the accurate motion control that relies on the close loop controller and supplies stable and consistent driving operation.
 

Transport Equipment

Nowadays, brushless direct current electric motors can be founded in a wide variety of transport equipment, such as electric or hybrid vehicles, electric aircraft, and electric bicycles, and so on. Many but not all-electric bicycles utilize brushless direct current electric motors which build into the wheel hub in some cases with the magnets connected to and spinning with the wheels. The same principle can also be found in electric self-balancing scooter's wheels.
 

Cordless Power Tools

Brushless direct current electric motors are also commonly used in a wide variety of cordless tools, such as some string trimmers, drills, drivers, and saws. The advantages of BLDC motors like a light in weight and high efficiency are important factors, especially for handheld cordless power tool selection.

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