Brushless motor

This post’s subject is about brushless motor. This type of motor is much used in drones and model airplanes for be light and has great rotation speed, making it good to move propellers. Not all drones use brushless motors. Are used also in coolers (computer’s fans).

How it works?

In DC motors, there are parts called brushes which serve to make sure that the motor keep rotating, those components aren’t necessary in a brushless motor. One notable feature of this motor is that the rotor has permanent magnet and the stator has electromagnets.

The difference between a brushed DC motor and a brushless motor.

To turn on this type of motor, you must turn on sequentially the coils in the stator to attract some rotor’s magnets and repel others, this way the motor rotate.

To turn on and control properly this type of motor, you must use the speed control. This is an example of electronic circuit made to control brushless motors. I will talk about this circuit’s functioning in another post.

Motors used in PC coolers have an electronic circuit with Hall-effect sensors to control the coils. I will talk about the Hall Effect and your applications in other post.

What is kV?

Brushless motors used in drones and model airplanes have the kV ranting, which relates rotations per minute (rpm) with the receiving voltage.

$kV=\frac{rpm}{V}$

Advantages and disadvantages

The vantages the brushless motors have over the brushed ones are:

The absence of brushes eliminates the electromagnetic interference caused by commutation;
Greater durability, because there is no weariness due to the brushes and the rotor has permanent magnet;
Greater speed because there is no limitation caused by the brushes.

The disadvantages are:

Brushed motors are expensive;
The speed control is expensive.

How to use it?

To use a brushless motor to drones or model airplanes, you will need a radiofrequency transmitter and a receiver. You can buy or make it if you have resources and technical knowledge.