harjakommutaatio

Harjakommutaatio, often referred to as brush commutation in English, is a process in DC electric motors that allows for the continuous rotation of the armature. It is the mechanism by which the direction of current in the armature coils is reversed at the correct moments. This reversal is essential for maintaining the torque that drives the motor's rotation.

The system typically consists of a commutator, which is a segmented cylinder attached to the armature shaft, and brushes, which are stationary electrical contacts that press against the commutator. As the armature rotates, the commutator segments also rotate. The brushes are positioned so that they bridge across adjacent commutator segments at the precise moment the current in a particular armature coil needs to be switched. This switching ensures that the magnetic forces acting on the armature coils always produce a torque in the same rotational direction.

Without effective commutation, the torque would reverse direction with each rotation of the armature, resulting in oscillatory motion rather than continuous rotation, or the motor would simply stall. The design and maintenance of the commutator and brushes are therefore critical for the proper functioning of DC motors. Wear and tear on these components, as well as sparking or arcing between the brushes and commutator, can degrade performance and lead to motor failure. Advanced DC motor designs may employ more sophisticated commutation techniques, such as electronic commutation, to overcome the limitations of mechanical brushes and commutators.