
Induction Motors - Rotating Field, Slip and Torque 167
Torque
0 N
s
Speed
Figure 5.18 Typical complete torque-speed characteristic for cage induction
motor
INFLUENCE OF ROTOR CURRENT ON FLUX
Up to now all our discussion has been based on the assump-
tion that the rotating magnetic field remains constant,
regardless of what happens on the rotor. We have seen how
torque is developed, and that mechanical output power is
produced. We have focused attention on the rotor, but the
output power must be provided from the stator winding, so
we must turn attention to the behaviour of the whole motor,
rather than just the rotor. Several questions spring