Number of Pole Pairs

nsync = synchronous speed f = frequency of the 3-phase power supply p = number of pole pairs of the 3-phase motor Kindly note that the above noted relation results in revs per second if the frequency unit is Hz.
Pole pair numbers 1 2 3 4 5 6
Synchronous speed (at 50 Hz) n [rpm] 3000 1500 1000 750 600 500
Synchronous speed (at 60 Hz) n [rpm] 3600 1800 1200 900 720 600
The rated full-load speed of three phase asynchronous motors is, due to slip, a few percent below the synchronous speed.