Calculate induction motor slip and what it reveals about loading.
Slip is roughly proportional to torque, so comparing measured slip with rated slip gives a non-invasive estimate of motor loading. Rotor current frequency is slip times supply frequency, which is why rotor losses are low at normal slip. Slip measurement is the standard field technique for finding oversized motors, which run at poor efficiency and power factor.
Motor Slip
Slip % = (n_s − n_r) ÷ n_s × 100; load ≈ slip ÷ rated slip
Slip % = (n_s − n_r) ÷ n_s × 100; load ≈ slip ÷ rated slip Slip is roughly proportional to torque, so comparing measured slip with rated slip gives a non-invasive estimate of motor loading. Rotor current frequency is slip times supply frequency, which is why rotor losses are low at normal slip.
Slip measurement is the standard field technique for finding oversized motors, which run at poor efficiency and power factor.
This calculator takes 3 inputs: Synchronous speed, Measured rotor speed, Rated slip at full load. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.