1. An alternator is a synchronous generator that converts mechanical power into alternating current electrical power. It works by using a rotating magnetic field and stationary armature windings to produce electricity. 2. Alternators can be classified as having either a salient pole rotor or cylindrical pole rotor. The power angle characteristic of an alternator is the curve showing the relationship between the total power developed and the load angle. 3. For both salient pole and cylindrical pole alternators, the power output increases proportionally with the load angle up to 90 degrees. At 90 degrees the machine reaches its steady state stability limit and will go out of synchronization if loaded further.