DC Generator : Working,Principle
An electrical generator is a machine which converts mechanical energy (or power) into electrical energy (or power).DC generator works on the principle of Faraday's Laws of Electromagnetic Induction.Faraday's Laws of Electromagnetic Induction:
According faraday's laws whenever a conductor cuts magnetic flux. dynamically induced e.m.f. is produced in it.this e.m.f. causes a current to flow if the conductor circuit is closed.energy conversion in the generator is based on the principle of the production of dynamically (or motionally) induced e.m.f in armature.
the amount of emf generated is
E=dφ/dt
We have two basic essential parts of an DC generator are
i) a magnetic field and (ii) a conductor or conductors which can so move as to cut the flux.
DC Generator Working Principle:
Working principle of dc generator can be explained with single loop generator concept.let us consider single loop coil inserted in magnetic (N-S)field as shown in the figure.assign loop edges with ABCD as marked..the magnetic field direction will be from N-S.assume you are rotating the coil
Step1:-
In this mode the dφ is maximum,because AB and CD are parallel to magnetic filed direction.field strength at CD and AB are not same so dφ exist.the out put voltage we E=dφ/dt.the current direction will be given by current can be determined by Flemming's right hand Rule. This rule says that is you stretch thumb, index finger and middle finger of your right hand perpendicular to each other, then thumbs indicates the direction of motion of the conductor, index finger indicates the direction of magnetic field,from Flemming's right hand Rule current flow from A to B ,C to D.
Step2:-
In this mode the dφ is minimum,because AB and CD are perpendicular to magnetic filed direction.field strength at CD and AB are same so dφ almost zero.hence we assume current is also zero.
Step3:-
In this mode the dφ is maximum,because AB and CD are parallel to magnetic filed direction.field strength at CD and AB are not same so dφ exist.the out put voltage we E=dφ/dt.the current direction will be given by current can be determined by Flemming's right hand Rule. Flemming's right hand Rule current flow from B to A ,D to C.
ALL DONE..but observe Step1 and Step3 we are getting AC in DC generator instead of DC to eliminate bi directional current we use slip rings.by using slip ring we convert bi directional current into uni directional current.Split ring are made out of a conducting cylinder which cuts into two halves or segments insulated from each other. The external load terminals are connected with two carbon brushes which are rest on these split slip ring segments.
DC Generator with slip rings:
DC Generator output waveform:
This is basic working principle of DC generator,explained by single loop generator model.
