A brushed-DC motor relies on coils of wire on a rotor, and a rigid motor frame--or stator--that positions permanent magnets around the rotor. Current through the windings creates a magnetic field that either attracts a winding to a magnet or repels it from a magnet. Contacts on the rotor, and brushes on the stator select the windings to power as the rotor turns.

You can find brushless-DC motors in appliances, medical instruments, and industrial equipment because they offer advantages over their brushed-DC-motor siblings. But before you can use a brushless-DC (BLDC) motor you need to understand how it works, and that leads to a quick review of DC-motor construction. BLDC motors use electronic commutation to switch coils on or off. This type of commutation falls into two categories: sensor-based or sensorless.

If a motor will operate at high temperatures, it may exceed the temperature ratings of Hall-effect sensors, and Hall-effect sensors might not operate reliably in the presence of high ambient magnetic fields. Eliminating sensors also reduces the number of connections with a motor. Consider sensorless commutation for applications that require a constant speed.