Definition
An electrical generator is a device which converts mechanical energy into electrical energy. This energy conversion is based on the principle of Faraday's law of electromagnetic induction. This states whenever there is a change in the magnetic flux associated with a conductor, an EMF is induced in it. This induced EMF causes a current to flow in the conductor circuit is closed.
An electrical generator is a device which converts mechanical energy into electrical energy. This energy conversion is based on the principle of Faraday's law of electromagnetic induction. This states whenever there is a change in the magnetic flux associated with a conductor, an EMF is induced in it. This induced EMF causes a current to flow in the conductor circuit is closed.
Therefore,
the two basic essential requirements of an electrical generator are:
1.
The magnetic field
2.
and the conductor which can move so as to cut the magnetic flux.
Working Principle of DC generator
Consider a DC generator operates on the principle of dynamically induced EMF. Let a simple loop generator which rotates a single turn rectangle of coil say ABCD about its axis in the magnetic field. Note that both the permanent magnet an electromagnet can be used to produce required magnetic field. The position of the rotating coil changes in the magnetic field flux linked with it also changes. Just an EMF is induced in the coil as accordance with the Faraday's law of electromagnetic induction which induced EMF is proportional to the rate of change of the linked magnetic flux. After every half rotation the sides ABCD of the loop swaps the positions. Just the direction of current flowing through them gets reversed. Such a current undergoing periodic directional reversal is known as alternating current. To change this bi-direction alternating current into directional DC current split rings are used. This rings are made of a conducting cylinder which is cut into the two half of segments insulated from each other by thin sheet of some insulating material like mica. The ring segments are also caped insulated from the central shaft and are connected to the ends of the coil and the carbon brushes.
Consider a DC generator operates on the principle of dynamically induced EMF. Let a simple loop generator which rotates a single turn rectangle of coil say ABCD about its axis in the magnetic field. Note that both the permanent magnet an electromagnet can be used to produce required magnetic field. The position of the rotating coil changes in the magnetic field flux linked with it also changes. Just an EMF is induced in the coil as accordance with the Faraday's law of electromagnetic induction which induced EMF is proportional to the rate of change of the linked magnetic flux. After every half rotation the sides ABCD of the loop swaps the positions. Just the direction of current flowing through them gets reversed. Such a current undergoing periodic directional reversal is known as alternating current. To change this bi-direction alternating current into directional DC current split rings are used. This rings are made of a conducting cylinder which is cut into the two half of segments insulated from each other by thin sheet of some insulating material like mica. The ring segments are also caped insulated from the central shaft and are connected to the ends of the coil and the carbon brushes.
Now let's discuss how the split rings change the bidirectional alternating current into unidirectional DC current. Let’s assume that the current is flowing along ABCD. Then the brush 1 is in contact with segment A which acts as a positive end of supply and brush 2 is in contact with Segment B which acts as the negative end supply. Therefore, the direction of current in the load resistance is from M to L. Now other half revolution direction of induced current in the coil reverses and its begins to flow along ABCD. Also position of segments A and B gets reversed and brush 1 comes into contact with segment B which now acts as a positive supply and brush 2 comes in contact with segment A which now acts as the negative supply. The direction of current in the load resistance still remains to be form M to L. The position of the brushes is also arranged that the change over the segments A and B from one brush to the other takes place on the plane of rotating coil is perpendicular to the plane of magnetic flux. When induced EMF in the coil is zero, then the similar to an AC generator current induced in the coil in a DC generator is also alternating. But due to the rectifying action of the split rings current across the external load become unidirectional. This actions of split Rings is known as commutator.
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