The working mechanism of brushless motors

The motor from a 3.5″ floppy disk drive. The coils, arranged radially, are made from copper wire coated with blue insulation. The well balanced rotor (upper right) has been removed and turned upside-down. The grey band inside its cup is a long term magnet.
A brushless DC electric motor (BLDC motor or BL electric motor), also referred to as electronically commutated electric motor (ECM or EC electric motor) and synchronous DC motors, are synchronous motors powered by DC electrical power via an inverter or switching power which generates an AC electric energy to drive each phase of the motor with a closed loop controller. The Transmission Chain controller provides pulses of current to the engine windings that control the swiftness and torque of the electric motor.

The construction of a brushless electric motor system is normally similar to a permanent magnet synchronous engine (PMSM), but can also be a switched reluctance motor, or an induction (asynchronous) motor.[1]

The benefits of a brushless electric motor over brushed motors are high power to weight ratio, high speed, electronic control, and lower maintenance. Brushless motors discover applications in such areas as computer peripherals (disk drives, printers), hand-held power tools, and vehicles which range from model aircraft to automobiles.
In an average DC electric motor, there are long term magnets externally and a spinning armature on the inside. The long term magnets are stationary, therefore they are known as the stator. The armature rotates, so that it is named the rotor.

The armature contains an electromagnet. When you operate electricity into this electromagnet, it generates a magnetic field in the armature that draws in and repels the magnets in the stator. Therefore the armature spins through 180 degrees. To keep it spinning, you have to modify the poles of the electromagnet. The brushes deal with this modify in polarity. They make contact with two spinning electrodes attached to the armature and flip the magnetic polarity of the electromagnet as it spins.
his setup works and is easy and cheap to manufacture, but it has a lot of problems:

The brushes eventually wear out.
Because the brushes are producing/breaking connections, you get sparking and electrical noi
The brushes limit the utmost speed of the engine.
Having the electromagnet in the center of the motor helps it be harder to cool.
The utilization of brushes puts a limit on how many poles the armature can have.
With the advent of cheap computers and power transistors, it became feasible to “turn the engine inside out” and eliminate the brushes. In a brushless DC motor (BLDC), you put the permanent magnets on the rotor and you move the electromagnets to the stator. Then you use a computer (linked to high-power transistors) to replenish the electromagnets as the shaft turns. This system has a variety of advantages:
Because a computer handles the motor rather than mechanical brushes, it’s more precise. The computer can also factor the velocity of the motor into the equation. This makes brushless motors more efficient.
There is absolutely no sparking and far less electrical noise.
There are no brushes to degrade.
With the electromagnets on the stator, they are very easy to cool.
You can have a lot of electromagnets on the stator for more precise control.
The only disadvantage of a brushless engine is its higher initial cost, but you can often recover that cost through the greater efficiency over the life of the motor.

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