The working mechanism of brushless motors

The electric motor from a 3.5″ floppy disk drive. The coils, arranged radially, are manufactured from copper wire covered with blue insulation. The well balanced rotor (upper right) has been taken out and turned upside-down. The grey ring inside its cup is a long term magnet.
A brushless DC electrical motor (BLDC electric motor or BL motor), also known as electronically commutated engine (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 generates 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 velocity and torque of the electric motor.

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

The benefits of a brushless engine over brushed motors are high capacity 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 a typical DC electric motor, there are long term magnets on the outside and a spinning armature inside. The long lasting magnets are stationary, so they are known as the stator. The armature rotates, so that it is called the rotor.

The armature contains an electromagnet. When you run electrical power 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 modify 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 has a lot of problems:

The brushes eventually degrade.
Because the brushes are making/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 motor inside out” and get rid of the brushes. In a brushless DC engine (BLDC), you place 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 system has a variety of advantages:
Because a computer settings the motor rather than mechanical brushes, it’s more precise. The computer may also factor the velocity 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 very easy to cool.
You can have a 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 can often recover that cost through the greater efficiency over the life of the motor.


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