The Function of a Commutator in a DC Generator
Even though we’ve already mentioned the commutators when we talked about the DC generators, or even if you’ve already heard about them, it’s important to delve deeper into the subject.
And why is it so important?
Because we consider the commutator as the rotor, which is the most important part of the DC generator, these are some of the reasons:
- It connects between the rotating armature conductors and stationary external circuits by the brushes.
- It converts the alternating current produced in armature conductors to a unidirectional current in the external load circuit.
- Sequentially it also converts the alternating torque to continuous torque in the armature in motor action.
The Commutator of DC Generator
Now we will deal with the commutator as a mechanical rectifier or a rotary electrical switch.
This mechanical rectifier commutates the alternating current produced in the DC generator’s armature winding into a direct current. It also keeps the torque from reversing its direction, and that happens because of the commutator.
Similarly, we can say that the commutator works like a bridge rectifier with the stationary brushes’ help.
We use alternating currents, such as electric light bulbs, electric heating elements, small electric motors like food mixers, vacuum cleaners, and so on.
So why do we commutate the alternating current? That’s a good question which takes us to huge electric motors. For instance, locomotives, ships, diesel motors, electric razors, producing aluminum, chlorine, and other industrial applications, which need a direct current to work correctly.
It is important to keep a continuous moving contact between the commutator segment and the brushes to ensure the continuous transformation of current from the rotating armature to the brushes.
Working of the DC Generator With the Commutator
Firstly, when the armature starts to rotate, the coil rotates between a positive brush and its consecutive negative brush.
So the current flows through the coil in a direction inward to the commutator segments.
With the help of a brush and the commutation period, which is approximately (1/500 sec), the coil is short-circuited.
And after this period, the armature coil rotates back between the negative brush and its succeeding positive brush.
So it is axiomatic that the current direction reverses away from the commutator segments. This reversing process of direction is the commutation.
The commutation process was completed by the end of the commutation period to avoid any damage to the commutator surface due to overheating or sparking.