Section 15.7: Starting of Induction Motors cont.
Rotor Resistance Techniques
As suggested by text Figure 15.10 (p. 560), increased rotor resistance yields higher torque at lower speed
Inserting (exogenous) resistance into the rotor (while starting) is strait-forward for wound-rotor motors since the rotor circuit is electrically accessible
In cage (rotor)-type machines, the skin effect phenomenon is used to automatically insert resistance in the rotor (on starting) as follows (next slide)
Starting Techniques Based on Rotor-resistance and Reduced Stator Voltage