explain the working and construction of DC genreator
Answers
1 dc generator Yoke (magnetic frame):
The yoke is the outer frame of the machine used to support and protect the internal parts, it’s made of permeability material processing sufficient mechanical strength and it also carries the magnetic field flux produced by field winding.
Pole cores and pole shoes:
dc generator Field windings:
Generally, we fabricate field winding of low resistive materials copper or aluminum, we can connect this field windings to the armature in series or shunt.
When we connect the windings in series, we use less numbered turns with large cross-section conductors, instead when they are shunted they would be in large turns with a less cross-section to withstand the supply voltage.
When the current pass through the winding coils the pole core become electromagnetism then produce the necessary magnetic flux.we take care to connect the field coils in a way that the poles are made of positive polarity.
Pole cores are the most important of the field magnet, they have this great importance as they help:
Establishing the required magnetic flux how! when the current pass through the field winding placed on this pole, the core becomes electromagnetic hence, it establishes the magnetic flux and this flux can be varied by varying the current through field winding.
Brushes and brush holders:
Brushes are important to us because we use them to ensure electrical connections between the rotating commutator and external load circuit because they collect current from commutator segments.
They have a rectangular block shaped usually made of carbon or graphite which are conducting materials.
The brushes are housed in the brush holders which are secured to the front end housing with clamps.
Brushes also gain added from its cheap coast, ability to minimize the sparking and facilitate the collection of current from rotating commutator to stationary terminals.
But Unfortunately they require high maintenance, and they reduce the terminal voltage due to brush contact drop.
Working principle of a DC generator: According to Faraday's laws of electromagnetic induction, whenever a conductor is placed in a varying magnetic field (OR a conductor is moved in a magnetic field), an emf (electromotive force) gets induced in the conductor.
Lenz's law is derived from Michael Faraday's law of induction. ... Eddy currents generated by electromagnetic induction circulate around the coils core or any connecting metallic components inside the magnetic field because for the magnetic flux they are acting like a single loop of wire.
