3 phase motor help (poles and rotor/ stator ratio)?

i have been given a question, ive managed to answer the first part but this part i am finding difficult:



Explain and show how a change in poles and/or rotor stator turns ratio could vary the slip and torque of an induction motor and the effect on motor speed any changes would have.



any help with this question would be greatley appreciated.3 phase motor help (poles and rotor/ stator ratio)?
If the supply frequency is 50Hz and the motor has two poles per phase (one north pole and one south pole), the motor will run at the synchronous speed, minus the slip speed (which is about 7% of the synchronous speed). This means that the rotor will turn at 3,000 - 180 = 2,790 RPM. There must be a substantial slip speed to ensure that the stator's rotating magnetic field, cuts the rotor bars and generates an EMF --- this is how the torque is produced.



Now we come to the hard part --- if we have four poles per phase, one complete cycle of the rotating magnetic field, will take one half of a revolution. This means that the speed of the rotor will be about 1,395 RPM.



Since power is the product of speed and torque, if the power remains constant and the speed decreases due to more poles per phase, the torque will increase. A 16 pole, 500 HP wound rotor motor, runs at about 175 RPM and produces enough starting torque to make your eyes water.