The working mechanism of brushless motors

The engine from a 3.5″ floppy disk drive. The coils, arranged radially, are manufactured from copper wire covered with blue insulation. The balanced rotor (upper correct) has been taken out and switched upside-down. The grey band inside its cup is a long term magnet.
A brushless DC electrical motor (BLDC engine or BL electric motor), also known as electronically commutated motor (ECM or EC electric motor) and synchronous DC motors, are synchronous motors powered by DC electrical power via an inverter or switching power supply which creates an AC electric energy to drive each phase 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 engine.

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

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

The armature contains an electromagnet. When you operate electricity into this electromagnet, it creates 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 need to change 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 as it spins.
his setup works and is easy and cheap to produce, but it includes a lot of problems:

The brushes eventually degrade.
Because the brushes are producing/breaking connections, you get sparking and electrical noi
The brushes limit the utmost 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 feasible to “turn the electric motor inside out” and eliminate the brushes. In a brushless DC engine (BLDC), you place the permanent magnets on the rotor and you move the electromagnets to the stator. Then you use a Conveyor Chain computer (linked to high-power transistors) to replenish the electromagnets as the shaft turns. This system 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 swiftness of the motor in to the equation. This makes brushless motors better.
There is 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 whole lot of electromagnets on the stator for more precise control.
The only drawback of a brushless electric motor is its higher initial cost, nevertheless, you could recover that cost through the higher efficiency over the life of the motor.


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