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Function of commutator in Dc generator (full details)

November 20, 2017
Function of commutator in Dc generator (full details)

Function of commutator in Dc generator

The function of commutator in Dc generator!! Yes, why wonder?  When we talk about the construction of Dc generator we talk in details about the commutator, so what is new? that’s very good and you are perfectly right.

We talk about the commutator that we consider it as the rotor and it’s the most important in Dc generator because:

  • It connects between the rotating armature conductors and stationary external circuit 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.

Function of commutator in Dc generator

That’s satisfied, but not the enough about the most important part of Dc generator you should know more we must look at it differently and that’s what we will try now together.

The commutator of Dc generator:

Now we deal with the commutator as a mechanical rectifier or a rotary electrical switch.

This mechanical rectifier commutate the alternating current produced in the armature winding of the Dc generator into a direct current and keep the torque from reversing its direction and that happens by the commutator and the help of the stationary brushes, we simply can say that the commutator works like a bridge rectifier.


Okay, no problem in this commutation, but we need alternating current in electric light bulbs, electric heating elements, small electric motors like food mixer, vacuum cleaners and so on.

So why we commutate the alternating current?

That’s a good question which takes us to very large electric motors like locomotives, ships, diesel motors, electric razors,  producing aluminum, chlorine and other industrial applications around us which only work perfectly with direct current

And we take care 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.

Wait! I need more explanation, that’s what I’d do, but we will be back to Working principle of Dc generator and remember how the coil moves to produce the required current and voltage.

working of dc generator with 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.

Then with the help of a brush and for the commutation period which is approximately (1/500 sec), the coil is short-circuited.

And after this period the armature coil re rotates between the negative brush and its succeeding positive brush.

So it is axiomatic that the current direction is reversed away from the commutator segments.

This reversing process of direction is the commutation.

And we careful to a have an ideal commutation that means:

The commutation process completed by the end of the commutation period to:

Avoid any damage to the commutator surface due to overheating due to sparking if the commutation completed during the commutation period.

finally, I hope to share this article “Function of commutator in Dc generator (full details)”