In this chapter, we learned that a step-down autotransformer could be used to reduce the starting current drawn by an induction motor. While this technique works, an autotransformer is relatively expensive. A much less expensive way to reduce the starting current is to use a device called Y-D starter (described earlier in this chapter). If an induction motor is normally D-connected, it is possible to reduce its phase voltage Vf (and hence its starting current) by simply re-connecting the stator windings in Y during starting, and then restoring the connections to D when the motor comes up to speed. Answer the following questions about this type of starter.
(a) How would the phase voltage at starting compare with the phase voltage under normal running conditions?
(b) How would the starting current of the Y-connected motor compare to the starting current if the motor remained in a D-connection during starting?