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 correct) has been taken out and turned upside-down. The grey band inside its glass is a long lasting magnet.
A brushless DC electric motor (BLDC motor or BL electric motor), also called electronically commutated electric motor (ECM or EC engine) and synchronous DC motors, are synchronous motors powered by DC electricity via an inverter or switching power supply which creates an AC electric current to drive each phase of the motor with a closed loop controller. The controller provides pulses of current to the motor windings that control the rate and torque of the motor.
The construction of a brushless motor system is normally similar to a long term magnet synchronous motor (PMSM), but may also be a switched reluctance electric motor, or an induction (asynchronous) motor.[1]
The advantages 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 ranging from model aircraft to automobiles.
In an average DC motor, there are permanent 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 run electrical power 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 maintain it spinning, you have to alter the poles of the electromagnet. The brushes handle this modify in polarity. They speak to 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 manufacture, but it has a lot of problems:
The brushes eventually wear out.
Because the brushes are making/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 helps it be harder to cool.
The usage of brushes puts a limit on how many poles the armature can have.
With the Auto Chain advent of cheap computers and power transistors, it became possible to “turn the engine inside out” and eliminate the brushes. In a brushless DC electric motor (BLDC), you put the long lasting magnets on the rotor and you move the electromagnets to the stator. You then use a computer (connected to high-power transistors) to charge up the electromagnets as the shaft turns. This technique has all sorts of advantages:
Because a computer regulates the motor 
rather than mechanical brushes, it’s more precise. The computer may also factor the speed of the motor into the equation. This makes brushless motors more efficient.
There is absolutely 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, but you can often recover that cost through the higher efficiency over the life of the motor.