Why is the field producing winding of a 3-phase induction motor made stationary?

A 3-phase induction motor has two windings viz stator winding supported by the stationary part of the machine and the rotor winding placed on the rotor. So far as the basic operation of the motor is concerned, it makes no difference which winding is located on the stator. The machine will function equally well with field producing winding as either the stationary or rotating element. Making the field winding stationary element eliminates the use of slip rings and brushes and, therefore, will result in a very trouble-free construction.