In all machine stator and rotor magnetic field rotates (stationary with respect to each other) at synchronous speed with respect to stationary observer.
Skin Effect: tendency of the current to crowd near the conductor surface.
Skin effect is proportional to frequency, conductor diameter and permiability. Skin effect increases effective resistance of conductor. In DC, no skin effect.
due to fractional pitch EMF can be approximately made into sine wave losses due to harmonics reduced saving in conductor material mechanical strength of coil is increased.
EXAMIANS