What is a Simple Loop Generator
An electrical generator is a machine which converts mechanical energy into electrical energy. The energy conversion is based on the principle of the production of dynamically (or due to motion) induced e.m.f. whenever a conductor cuts magnetic flux, dynamically induced e.m.f. is produced in it according to Faraday’s Laws of Electromagnetic Induction. This e.m.f. causes a current to flow if the conductor circuit is closed.
Essential Parts of Electric Generator
The basic essential parts of an electrical dc generator are
- Magnetic field
- Conductor or conductors
- Motion of conductor or conductors with respect to magnetic field
The direction of induced emf (hence current) is given by Flemings right hand rule.
Working of Electric Generator
Consider a single turn rectangular cooper conductor “ABCD” rotating in a clockwise direction in a uniform magnetic field at a constant speed as shown in figure below. As the loop is rotated by some mechanical means the flux linking with the loop changes continuously, therefore, emf is induced in the loop. The magnitude of emf induced is directly proportional to the rate of change of magnetic field.
- When the loop is in position no. 1 the generated e.m.f. is zero because the coil sides (AB and CD) are cutting no flux but are moving parallel to it. This position will be taken as starting position.\\\;\\\;\;\;\;
- When the loop is in position no. 2, the coil sides are moving at an angle to the flux and, therefore, a low e.m.f. is generated as indicated by point 2.\\\;\\\;\;\;\;
- When the loop is in position no. 3, the coil sides (AB and CD) are at right angle to the flux and are, therefore, cutting the flux at a maximum rate. Hence at this instant, the generated e.m.f. is maximum as indicated by point 3.\\\;\\\;\;\;\;
- At position 4, the generated e.m.f. is less because the coil sides are cutting the flux at an angle.\\\;\\\;\;\;\;
- At position 5, no magnetic lines are cut and hence induced e.m.f. is zero as indicated by point 5.\\\;\\\;\;\;\;
- At position 6, the coil sides move under a pole of opposite polarity and hence the direction of generated e.m.f. is reversed. The generated e.m.f. is less because the coil sides are cutting the flux at an angle. \\\;\\\;\;\;\;
- At position 7, the coil sides are at right angles to the flux and cutting the flux at maximum rate. Hence the generated emf is maximum but in opposite direction.\\\;\\\;\;\;\;
- At Position 8, The coil sides are at an angle to flux, therefore low emf is generated as shown in figure.\\\;\\\;\;\;\;
- At Position 9, The coil sides are reach back to position 1, the flux cut by coil sides are zero , therefore emf generated is zero.\\\;\\\;\;\;\;
Note that e.m.f. generated in the loop is alternating one. It is because any coil side, say AB has e.m.f. in one direction when under the influence of N-pole and in the other direction when under the influence of S-pole. If a load is connected across the ends of the loop, then alternating current will flow through the load. The alternating voltage generated in the loop can be converted into direct voltage by a device called commutator. We then have the d.c. generator. In fact, a commutator is a mechanical rectifier.