What is a brushless motor, and why is it marked as a good thing? Are “brushed motors” common?
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First understand how an electric motor works. Its basically magnets pushing against other magnets to make them spin. You have a spinning magnet in the middle called a rotor being pushed by magnets around the outside called the stator. As the rotor spins you need to change the magnetic field around in order to keep it aligned properly to keep applying force.
One of the easiest ways to do this is with brushes and a commutator. Since the rotor is spinning, you can make the rotor out of electromagnets (coils of wire) and have contacts that use the rotation of the rotor itself to keep changing the magnetization of the rotor. These brushes rub against the commutator in physical contact. Thats great, except physical contact means that the brushes wear over time and have to be replaced. They are usually made out of something like graphite that wears into dust (which can also be a problem).
The alternative is a brushless motor. Since it isn’t using brushes, it can’t rely on the physical contact against the spinning rotor to change the magnetization. It also means that the center probably can’t be an electromagnet, and permanent magnets usually aren’t quite as strong. To do this requires extra sensors to know where the rotor is and some more complicated control circuitry to power it properly. The upside is that there are no brushes to wear out, and this extra control circuitry allows you to do fancier stuff to control the motors more precisely.
There are also induction motors which are also brushless but use a different mechanism. They induce magentism in the rotor, which isn’t normally magnetic, but don’t have the same kind of control as what we usually call ‘brushless motors’ as they just make use of the constant changing of their AC power source so they run at a preset speed.
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