Motors and Drives: AC Induction Motor--Speed and Slip
Part 7 of the Motors and Drives Series describes how ac induction motors get their base speeds and how to calculate slip.
Speed and Slip
Speed(rpm) = (120 * F) / #Poles
%Slip = (Ssync – Sact) / Ssync * 100, Slip(RPM) = StatorRPM - RotorRPM