Sector detection using sensors

First, in order to control the rotor, its angular position and velocity must be measured using sensors such as Hall effect sensors. The Hall sensor does not provide information about the exact position of the rotor within the sector, it only detects when the rotor moves from one sector to another, which is the only input needed to determine when the motor is commutated.

However, each time the rotor crosses a sector, it is necessary to determine which of the three phases must be switched with it. The correct phase is specified by the commutation logic circuit.

Commutation is performed using commutation logic circuits

The commutation logic circuit calculates the switching mode of the three - phase inverter. In the commutation logic table, the letters A, B and C represent the three phases of the motor respectively. The high end of the three-phase inverter is labeled H, and the low end is labeled L. If the rotor is in the first sector, the commutation logic selects the top switching mode, which determines that the high end switch of phase A and the low end switch of phase C are on.

As the rotor moves to another sector, the logic accordingly selects the next switching mode, which is sent to the three-phase inverter. In summary, the sensor decides when to switch phases, and the commutation logic determines the correct phase to be energized each time the phase is switched. This is how the motor rotates.