Explain the Construction of Synchronous Machines?
Basically all synchronous machines require a DC excited field winding in order to produce magnetic flux. For majority of machines, this DC winding is located on the rotor since the problems of getting a large field current via brushes and sliprings or producing it in the rotor are far less difficult than collecting high voltages of the order of 22- kV via a slipring system.
The 3-phase AC winding is therefore on the stator and is often referred to as the armature winding (the term armature for any type of machine always refers to the power winding handling the greatest amount of power in the machine). Such a construction where the excitation is provided from the rotor and the actual power winding is accommodated in the stator slots is obviously totally opposite to that of a DC machine. It is usually termed as an "inside-out" construction.