From Figure 24, we note that the inertia factor
of the connected load may vary from 1 to 100. For
the specific motor covered by Figure 22, pull-in
can be affected at 8% slip with normal load WK2
.
However, with an inertia factor of 100, the motor
must reach 99.2% of synchronous speed on the
cage winding before the motor will pull into step
on application of excitation. A motor will therefore
have a much higher “load” pull-in torque when
driving a load having a low inertia factor than
with a load having a high inertia factor.