What is the difference between a three phase alternator and a three phase synchronous motor?

 

Very little, except one milks the cows, the other cows the milk.

So tell us more.

 

They are very close in design except the alternator is a Generator and the synchronous motor is build almost the same, except as well as the wound rotor fed via slip rings, it has a squirrel cage induction rotor.
Initially the S.M. is ran up as an induction motor until the near synchronism is detected via the slip rings, at this point, DC is injected into the rotor coil and the motor comes up to synchronism.
Max.

 

@MaxHeadRoom
An elegantly succinct explanation.