Commutator Action

The commutator converts the AC voltage produced within the rotating loop into a DC voltage. It also serves as a means of linking the brushes to the rotating loop. The aim of the brushes is to connect the produced voltage to an external circuit.  In sequence to do this, every brush have to make contact along with one of the ends of the loop. Because the loop or armature rotates, a direct connection is impractical. Alternatively, the brushes are linked to the ends of the loop by the commutator.

                                                 Figure: Commutator Segments and Brushes

Within a simple one-loop generator and the commutator is made up of two semicylindrical pieces of a smooth conducting material, generally copper, divided through an insulating material, as display in Figure.In each half of the commutator segments are permanently attached to one end of the rotating loop, and the commutator rotates along with the loop.  The brushes, commonly made of carbon, rest against the commutator and slide with the commutator as it rotates.  This is the means through that the brushes make contact within each end of the loop.

Every brush slides with one half of the commutator and then along the other half.  An brushes are positioned on opposite sides of the commutator; it will pass from one commutator half to the other at the instant the loop reaches the point of rotation, at that point the voltage which was induced reverses the polarity.    Each time the ends of the loop reverse polarity and a brushes switch from one commutator segment to the further.  That means in which one brush is always positive along with respect to another. The voltage among the brushes fluctuates in amplitude (size or magnitude)  among  zero  and  a few  maximum  value,  but  is  always  of  the  similar  polarity shown in the figure.  Within this manner, commutation is accomplished in a DC generator.

One most important point to remember is that, as the brushes pass from one segment to the other, there is an immediate when the brushes contact both segments at the similar time.  The induced voltage at this point is zero.  Extremely high currents would be generates due to the brushes shorting the ends of the loop together if the induced voltage at this point were not zero.  The point, at that the brushes contact both commutator segments, whenever the induced voltage is zero, is known as the "neutral plane."