The agricultural Chain engine from a 3.5″ floppy disk drive. The coils, arranged radially, are made from copper wire covered with blue insulation. The well balanced rotor (upper 
correct) has been removed and switched upside-down. The grey band inside its glass is a permanent magnet.
A brushless DC electrical motor (BLDC motor or BL motor), also referred to as electronically commutated engine (ECM or EC electric motor) and synchronous DC motors, are synchronous motors powered by DC electricity via an inverter or switching power which produces an AC electric energy to drive each stage of the motor with a closed loop controller. The controller provides pulses of current to the motor windings that control the quickness and torque of the engine.
The construction of a brushless electric motor system is typically similar to a permanent magnet synchronous motor (PMSM), but can also be a switched reluctance engine, or an induction (asynchronous) motor.[1]
The benefits of a brushless motor over brushed motors are high power to weight ratio, high speed, electronic control, and lower maintenance. Brushless motors find applications in such areas as pc peripherals (disk drives, printers), hand-held power tools, and vehicles ranging from model aircraft to automobiles.
In an average DC motor, there are permanent magnets on the outside and a spinning armature on the inside. The long lasting magnets are stationary, so they are called the stator. The armature rotates, so it is called the rotor.
The armature contains an electromagnet. When you operate electrical power into this electromagnet, it generates a magnetic field in the armature that attracts and repels the magnets in the stator. Therefore the armature spins through 180 degrees. To maintain it spinning, you need to change the poles of the electromagnet. The brushes handle this alter in polarity. They make contact with two spinning electrodes mounted on the armature and flip the magnetic polarity of the electromagnet since it spins.
his setup works and is simple and cheap to produce, but it includes a lot of problems:
The brushes eventually wear out.
As the brushes are producing/breaking connections, you get sparking and electrical noi
The brushes limit the maximum speed of the motor.
Having the electromagnet in the heart of the motor makes it harder to cool.
The utilization of brushes puts a limit about how many poles the armature can have.
With the advent of cheap computers and power transistors, it became possible to “turn the motor inside out” and get rid of the brushes. In a brushless DC motor (BLDC), you put the permanent magnets on the rotor and you move the electromagnets to the stator. You then use a computer (linked to high-power transistors) to charge up the electromagnets as the shaft turns. This technique has all sorts of advantages:
Because a computer handles the motor instead of mechanical brushes, it’s more precise. The computer can also factor the rate of the motor into the equation. This makes brushless motors more efficient.
There is no sparking and much less electrical noise.
There are no brushes to degrade.
With the electromagnets on the stator, they are extremely 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, nevertheless, you can often recover that cost through the higher efficiency over the life of the motor.