Control Principle of DC Brushless Motor

To make the motor rotate, the control sector should find the current position of motor rotor sensed by the hall-sensor, then decide to start (or turn off) the sequence of power transistor in the inverter according to the stator winding, has the electric current flow through the motor coil in order to produce consequent (or reverse) rotating magnetic field and interact with the magnet of the rotator, in this way, the motor will rotate clockwise/counterclockwise.

When the motor rotor rotates to the place where the hall-sensor senses another set of signals, the control sector starts the next set of power transistors, cycle in this way, the motor can continue to rotate in the same direction until the control sector decides to making the motor rotator stop, then it turns off the power transistor (or just open the lower arm power transistors). To have the motor rotator runs counterclockwise, the starting order of power transistors should be in an opposite direction.