Brushless Motor -- Power Heart of Electric Machines
Are you curious why today's UAV can hover lightly for tens of minutes, power tools no longer emit an annoying buzz when running, and even the acceleration of electric cars can be as smooth as silk? Behind these lies a common “power heart” - the brushless motor.
This innovation, born in the 1960s, is breaking through the shackles of traditional machinery in a disruptive way: the wear and tear of the brush structure is discarded, and precise magnetic field switching is realized through electronic controllers. Nowadays, BLDC motors are widely used in computer hard disk, UAV, electric power tools, electric car, and many other fields.
1. The Basic Structure of BLDC Motor
Stator: The stator of BLDC motor is usually made of multiple electromagnetic coils. These coils generate a rotating magnetic field through electric current. Unlike the rotor of a brushed motor, the stator is fixed and immobile.
Rotor: The rotor is generally made of permanent magnetic material. The rotor interacts with the magnetic field of the stator, which is controlled by an external current to produce a torque that drives the rotor to rotate. The polarity of the rotor changes according to the current switching in the stator coil.
Electronic Commutator: Since there are no brushes or mechanical commutators, the BLDC motor requires an electronic commutator to control the on/off of the current to change the polarity of the stator solenoid coils, which in turn controls the rotor rotation. Hall sensors are usually used to detect the position of the rotor and realize the commutation.
2. The Types of BLDC Motor
Inner Rotor: The rotor of inner rotor motor locates in the motor and the stator rotates around the rotor. Internal rotor motor typically has higher speed and higher power densities for applications that require high speed operation.
Outer Rotor: The rotor of the outer rotor locates outside of the motor, and the stator is located in the inner ring of the motor. External rotor motor typically has higher torque and lower speed for applications that require higher torque.
3. Pros & Cons of BLDC Motor
Pros:
Brushless motor has no brush friction, thus it is usually more compact in structure, that’s why it is smaller both in size and weight. This also illustrates why it has lower loss of power and high operating efficiency.
Compared to brushed motor, brushless motor has higher energy-efficiency ratio, providing longer battery life and lower energy consumption, making it particularly suitable for energy-efficient applications such as premium home appliances, medical equipment, electric vehicles and portable devices.
Besides, without friction of the brush and the commutator makes it rarely requires maintenance. Its lifespan far exceeds that of brushed motor, making it appropriate for long-time working and high-loaded environment.
Cons:
Due to the complex electronic control system requiring precise electronic drive and additional drive circuitry, brushless motor is inherently more expensive and increases the overall system complexity and cost compared to brushed motor.
Furthermore, brushless motor typically exhibits low starting torque, making it unsuitable for applications demanding high initial torque without a specially designed drive circuit to achieve smooth starting. However, despite these factors, brushless motor excels in applications prioritizing high efficiency, long lifespan, low noise, and stable performance. Consequently, brushless motor is particularly well-suited for demanding fields such as UAVs, EVs, premium home appliances, and robotics.
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