BLDC Six-Step Commutation

Try this

1. Lower the duty to about 5% and let it turn slowly. The yellow arrow (stator field) jumps 60 degrees at a time and the red N pole follows it. Energised coils glow orange where current enters and blue where it leaves.
2. On the inverter board, compare the lit MOSFETs with the highlighted row of the switching table. Those are the high-side and low-side switches that are on. Current flows from the high-side phase to the low-side phase; the third phase floats.
3. The step advances the moment a Hall value changes. All the firmware does is read three Hall bits and look up the switch combination in this table.
4. Press Single step to stop after each step. In the commutation diagram, find where the Hall signals and phase voltages change.
5. Raise the duty and it speeds up. The order of combinations stays the same; only the average applied voltage grows.

Why the field must lead

Torque is greatest when the stator field is 90 degrees ahead of the rotor magnet. Six-step drive can only move the field in 60-degree jumps, so that angle swings between 60 and 120 degrees. Torque rises and falls a little across that range: this is torque ripple.

Rotating the field continuously to remove that ripple is what FOC does.

Limits of the model

The rotor is simplified to one pole pair, and back-EMF and current lag are left out. The lab is for seeing how switch order relates to the Hall sensors; the speed shown is not a real motor figure.