Pole Number and Synchronous Speed

Question 1

for a 4 pole machine

Answer 1

as the rotr makes one rev, each group of stator conductors (in each slot) experiences 2x as many changes in flux as those in pole case

Question 2

if airgap is sinosoidally flucatuating

Answer 2

staor has 4 groups of conductors and they are connected in series, 2x as many changes in flux as in the 2 pole case an the peak val and freq of induced emf is doubled assumes that the rotor is still rotating at original angular speed

Question 3

to have same freq and peak val of 2 pole case

Answer 3

half speed, implies that if there are more pole pairs, rottion of rotor and the airgap flux rotation can be made smaller

Question 4

how to find direction of machine rotation

Answer 4

by convention, phasors are rotating anti-clockwise
imagine all the
phasors are rotating in this direction and decide which phasor is leading (or always
ahead of) another.