The engine from a 3.5″ floppy disk drive. The coils, arranged radially, are made from copper wire coated with blue insulation. The balanced rotor (upper correct) has been eliminated and turned upside-down. The grey ring inside its cup is a long term magnet.
A brushless DC electric motor (BLDC electric motor or BL engine), also known as 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 which generates an AC electric current to drive each stage of the motor with a closed loop controller. The controller provides pulses of current to the engine windings that control the acceleration and torque of the motor.
The construction of a brushless motor system is normally similar to a permanent magnet synchronous motor (PMSM), but may also be a switched reluctance motor, 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 discover applications in such locations as pc peripherals (disk drives, printers), hand-held power tools, and vehicles which range from model aircraft to automobiles.
In an average DC motor, there are long term magnets on the outside and a spinning armature on the inside. The permanent magnets are stationary, so they are called the stator. The armature rotates, so that it is called the rotor.
The armature contains an electromagnet. When you run electricity into this electromagnet, it creates a magnetic field in the armature that attracts and repels the magnets in the stator. Therefore the armature spins through 180 degrees. To keep it spinning, you need to alter the poles of the electromagnet. The brushes manage this change 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 easy and cheap to produce, but it includes a lot of problems:
The brushes eventually Auto Chain degrade.
Because the brushes are producing/breaking connections, you get sparking and electrical noi
The brushes limit the maximum speed of the engine.
Having the electromagnet in the center of the motor helps it be harder to cool.
The usage of brushes puts a limit about how many poles the armature can have.
With the advent of cheap computers and power transistors, it became feasible to “turn the motor inside out” and get rid of the brushes. In a brushless DC engine (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 replenish the electromagnets as the shaft turns. This technique has all sorts of advantages:
Because a computer controls the motor rather than mechanical brushes, it’s more precise. The computer may also factor the acceleration of the motor into the equation. This makes brushless motors better.
There is no sparking and much 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 whole lot of electromagnets on the stator for more precise control.
The only drawback of a brushless engine is its higher initial cost, but you could recover that cost through the higher efficiency over the life span of the motor.