Before understanding the working principle of brushless motors, let's first learn the right-hand screw rule two (ampere rule two), as shown in the following figure:

When we hold the solenoid with the right hand, the four fingers point to the direction of the current, then the end pointed by the thumb is the N pole of the solenoid, and if the current is in the opposite direction, the north and South Pole are switched positions.

As shown in the figure above, we wind the stator around the coil and pass a certain current through the coil to generate a magnetic field. Lorentz's law of force states that as long as a current-carrying conductor is placed in a magnetic field, it will experience a force. Due to the reaction force, the magnet will experience equal and opposite forces. When the coil through the current, will produce a magnetic field, the magnetic field is driven by the stator's magnetic pole, the same pole repel each other, the opposite pole attracts each other, if you continue to change the direction of the coil current, then the rotor induced by the magnetic field of the magnetic pole will continue to change, then the rotor will be rotating under the action of the magnetic field.

The switching sequence of the current is mainly realized by the Hall sensor, which is mainly used to determine the conduction Angle of the power transistor in the electronic commutation circuit drive circuit, so as to determine the magnetic state of the armature field. The position of the pole of the rotor permanent magnet relative to the stator armature winding is detected by it so as to determine the switching sequence of the power transistor in the electronic commutation drive circuit.

In addition to Hall magnetic sensors, brushless motors can also use other sensors, such as photoelectric and electromagnetic sensors.