The basic purpose of commutation is to ensure that the torque acting on the armature is always in the same direction. The voltage generated in the armature is essentially alternating, and the commutator converts it into direct current; in short, the commutator Turn the coil on and off to control the direction the electromagnetic field points. On one side of the coil, the current should always "flow away", on the other hand, the current should always flow "toward", which ensures that the torque is always generated in the same direction; otherwise, the coil will rotate 180 degrees in one direction, and then Switch direction.
The commutator itself is a split ring, usually made of copper, and each part of the ring is connected to each end of the armature coil. If the armature has multiple coils, the commutator will also have multiple segments-one at each end of each coil. The spring-loaded brushes are located on both sides of the commutator and contact the commutator when the commutator rotates to provide voltage for the commutator sheet and the corresponding armature coil.
When the brush passes through the gap in the commutator, the supplied charge switches the commutator segment, and the commutator segment switches the electrical polarity of the armature coil. This switching of the coil polarity maintains the rotation of the armature in one direction. The voltage between the brushes fluctuates between zero and a maximum value, but always maintains the same polarity.