Dynamo (DC Generator)
A dynamo is a machine in which mechanical energy is changed into electrical energy in the form of direct current. In automobiles, dynamo has a dual function for lighting and charging the battery.
The essential parts of dynamo are:
- Field magnet
- Armature
- Commutator
- Split rings
- Brushes
Armatures and field magnets differ in dynamo and alternator. In the dynamo, the field magnets are stationary and the armature rotates while in an alternator, armature is stationary (stator) and the field magnet (rotor) rotates.
In a dynamo, ac waveform or the sine wave produced by an a.c. generator is converted into d.c. form by the split ring commutator. Each half of the commuter is connected permanently to one end of the loop and the commutator rotates with the loop. Each brush presses against one segment of the commutator. The brushes remain stationary while the commutator rotates. The brushes press against opposite segments of the commutator and every time the voltage reverses polarity, the split rings change position. This means that one brush always remains positive while the other becomes negative, and a d.c. fluctuating voltage is obtained across the brushes.
In place of slip ring, there are two split rings R1 and R2 which are the two half of the same ring. The ends of the armature coil are connected to these rings and the ring rotates with the armature and changes the contact with the brushes B1 and B2. This part of the dynamo is known as commutator.
When the coil is rotated in the clockwise direction, the current produced in the armature is a.c. but the commutator changes it into d.c. in the outer circuit.