I didn't see any standard amount. For 50 (60) Hz motors, I0/In (no-load current/rated current) decreases with motor power from 0.5 to 0.8 (in sub kW power range) to 0.2 to 0.3 in the high power range, but it increases with the number of pole pairs. For low airgap flux densities, the no-load current tends to be smaller. A typical magnetization curve is shown in following picture for motors in the kW power range at 50 (60) Hz. The I0 and In are no load and full load stator phase currents and F1m0
The no load (zero rotor current) design airgap flux density is Bg1 = 0.6 – 0.8T for 50 (60) Hz induction motors and goes down to 0.4 to 0.6 T for (400 to 1000) Hz high speed induction motors, to keep core loss within limits.
Based on metioned formula, the no-load current (I0
) may be calculated with the number of turns/phase W1 and the stator winding factor Kw1 already known. Varying as the value of Bgm desired the magnetization curve–Bgm(F1m)–is obtained.