Synchronous generator constructional diagram

A synchronous generator (alternator) has two main parts, the stator (armature) and the rotor (field).

   Stator frame (cast iron / steel)
  +---------------------------------+
  |  Stator core (laminated steel)  |
  |   +-------------------------+   |
  |   |  armature winding in    |   |
  |   |  slots (3-phase)        |   |
  |   |    +---------------+    |   |
  |   |    | Rotor (field) |    |   |
  |   |    |   N   [shaft] |    |   |
  |   |    |       S       |    |   |
  |   |    +---------------+    |   |
  |   +-------------------------+   |
  +---------------------------------+
    Slip rings + brushes -> DC supply
    (exciter) to field winding
    Prime mover coupled to the shaft

Components:

1. Stator frame: the outer cast-iron or steel body that supports the core and protects the machine.
2. Stator core: laminated silicon-steel stampings with slots on the inner surface; the laminations reduce eddy-current loss.
3. Armature winding: a three-phase winding placed in the slots, in which the emf is induced and from which the output is taken.
4. Rotor: carries the DC field winding; it is either salient-pole (low speed, hydro) or cylindrical (high speed, turbo).
5. Field winding: supplied with DC through slip rings and carbon brushes, producing the main flux.
6. Exciter: a small DC source (a DC generator on the shaft or a static rectifier) that supplies the field current.
7. Shaft and bearings: transmit the prime mover's torque to the rotor.
8. Air gap and cooling system: a small air gap separates the rotor and stator, and fans or ducts carry away the heat.