Rotation principle of brushless motor

The following is an introduction to the rotation principle of a brushless motor. I will explain the movement of the rotation principle of a brushless motor using still images and text, so please use your imagination to understand.

① Rotate counterclockwise from the initial state

Coil A is at the top, and the power supply is connected to the brush, with the left side as (+) and the right side as (-). A large current flows from the left brush through the commutator to coil A. This is a structure in which the upper part (outside) of coil A becomes the S pole.

Since 1/2 of the current in coil A flows from the left brush to coils B and C in the opposite direction to coil A, the outer sides of coils B and C become weak N poles (indicated by slightly smaller letters in the figure).

The magnetic fields generated in these coils and the repulsive and attractive effects of the magnets cause the coils to be forced to rotate counterclockwise.

② Further counterclockwise rotation

Next, assume that the right brush is in contact with both commutators while the coil A is rotated 30° counterclockwise.

The current of coil A continues to flow from the left brush to the right brush, and the outside of the coil remains at the S pole.

The same current as that of coil A flows through coil B, and the outside of coil B becomes the stronger N pole.

Since both ends of coil C are short-circuited by the brushes, no current flows and no magnetic field is generated.

Even in this case, there is a counterclockwise rotation force.

From ③ to ④, the upper coil is continuously subjected to the force moving to the left, and the lower coil is continuously subjected to the force moving to the right, and continues to rotate counterclockwise.

When the coil rotates to states ③ and ④ every 30°, when the coil is located above the central horizontal axis, the outer side of the coil becomes the S pole; when the coil is located below, it becomes the N pole, and this movement is repeated.

In other words, the upper coil is repeatedly subjected to a force moving to the left, and the lower coil is repeatedly subjected to a force moving to the right (both in a counterclockwise direction). This causes the rotor to always rotate counterclockwise.

If power is connected to the opposing left (-) and right (+) brushes, magnetic fields in opposite directions are generated in the coil, so the force applied to the coil is also in the opposite direction, causing clockwise rotation.

Additionally, when the power is disconnected, the brushed motor's rotor stops spinning because there is no magnetic field to keep it spinning.