(a) Name the three main types of a.c. motor and explain the use to which they are put in marine engineering. (6)

(b) A four pole motor is fed at 440 V and takes a armature of 50 A. The resistance of the armature circuit is 0.28 ohm. The armature winding is wave connected with 888 conductors and the useful flux per pole is 0.023 wb. Calculate the speed. (10)