Commutation and armature construction in real DC machines
Commutator- is an electrical rotating switch in a particular type of generators as well as
motors.
- mainly used to overturn the direction of current among the external circuit & rotor.
- The brushes or electrical contacts are made with a carbon press material
- The armature windings are allied to the segments of the commutator.
- The applications of commutators include DC (direct current) machines like DC generators,
numerous DC motors, as well as universal motors.
- In a DC motor, the commutator provides electric current to the windings.
- By changing the direction of current within the revolving windings every half turn, a torque
(steady revolving force) will be produced.
Commutator Construction and Working
a commutator can be built with a set of contact bars that are set toward the revolving shaft of a
DC machine, and allied to the armature windings.
shaft turns, the commutator will reverse the current flow within a winding.
For a particular armature winding, once the shaft has completed the one-half turn, then the
winding will be connected so that current supplies through it in the reverse of the first direction.
In a DC motor, the armature current causes the set magnetic field to use a rotating force,
otherwise a torque over the winding for making it revolve.
In a DC generator, the mechanical torque can be applied in the direction of the shaft to
maintain the armature winding motion via the stationary magnetic field, stimulating a
current within the winding.
In these two cases, Sometimes, the commutators will reverse the direction of current flow
throughout the winding so that the flow of current within the circuit which is external to the
machine maintains in only one direction.
Function of Commutator in DC Machines
Commutator in DC Motor
The commutator in case of a DC motor, it reverses the flow of current which is accessible from a DC
source at the exact time while the armatures coil crosses the magnetic unbiased axis.
keep a uni-directional torque
the commutator will change the direct current (DC) into alternating current (AC).
Commutator in DC Generator
The commutator in case of a DC generator, the induced e.m.f within the armature coil will change in
nature.
Consequently, the flow of current in the armature coil will also be changed.
This current will be reversed by the commutator at the exact time while the armatures coil crosses the
magnetic unbiased axis.
So, the load which is external to the generator will get a uni-directional current otherwise DC.
Slip Ring Commutator
A slip ring commutator is an electro-mechanical device, used to allow the power transmission as well
as electrical signals from an immobile to a revolving structure.
can be utilized in any kind of electro-mechanical system that needs revolution while power transmitting.
A slip ring commutator is a technique of building an electrical connection throughout a rotating
assembly.
it is an electric communication device that permits the flow of energy among two electrical
rotating elements in a motor.
Slip Ring Commutator Construction
slip ring commutator construction is, consists of immobile graphite otherwise brush which is
known as metal contact which wipes on the exterior diameter of a revolving metal ring.
When the metal ring twists, the flow of electric current otherwise signal is performed through the
immobile brush toward the metal ring for making the connection.
An extra ring or brush gatherings are stack along with the revolving axis if more than a single
electrical circuit is required.
Types of Slip Rings
as Mercury-wetted, Pancake, and Wireless.
