Chapter 1


Machines ranging from simple devices like drills to complex equipment like industrial robots all make use of brushless DC motors that convert electrical energy into rotational motion.

Brushless DC motors, also referred to as BLDC motors, offer many advantages over their brushed counterparts. BLDC motors provide higher efficiency and require lower maintenance, which is why they have replaced brushed motors in many applications.

Both types of motors operate based on a similar principle, in which the rotational motion is generated through the attraction and repulsion of magnetic poles of permanent and electromagnets. However, the way these motors are controlled is very different. BLDCs require a complex controller to convert a single DC power to three-phase voltage, whereas a brushed motor can be controlled by regulating the DC voltage.

Interaction between an electro- and permanent magnet

Brushed DC motors

  • High maintenance due to worn brushes
  • Low efficiency
  • Easy control (DC voltage)
Brushless DC motor

Brushless DC motors (BLDC)

  • Low maintenance
  • High efficiency
  • Complex control (DC to AC)
Brushless DC motor controlled by six-step commutation