The present-day electrical power system generally generates, transmits and distributes in the form of alternating currents.
- Alternator or synchronous generator is an electrical machine which generates three-phase power from mechanical power.
- The alternator is the largest energy converter found in the world.
Fig shows Alternator-
Construction of an Alternator:
- An alternator or synchronous generator works on the principle of electromagnetic induction as a dc generator
- When the conductor is placed in a rotating magnetic field then they induced emf in the conductor.
- In dc generator armature paced in rotor and field placed in the stator.
- The alternator also has field and armature winding but it is placed differently from dc generator, Armature is placed on stator and field is placed on rotor because of production of alternating currents.
Advantages of Stationary Armature–Rotating Field Alternator?
As we know, field winding of an alternator is placed on rotor and armature winding is placed on stator and rotor connected to DC supply through two slip ring.Armatures are stationary and fields placed in rotor due to the following advantages:
This is because we give supply to the field winding and generate current is taken from armature winding.
- As the rating of an alternator is in MVA or KVA, the voltage and current production will be very high. It is easier to insulate stationary winding for high voltages for which the alternators are usually designed.
- They are not subjected to centrifugal forces and also extra space is available due to the stationary arrangement of the armature. (Perfect mechanical balance)
- The stationary 3-phase armature can be directly connected to the load without unreliable slip rings and brushes.
- Only two slip rings are required for d.c. supply to the field winding on the rotor, so it makes it economical.
- Due to the simple construction of the rotor, higher speed of rotating d.c. the field is possible. This increases the output obtainable from a machine of given dimensions.