A certain application requires power at a frequency of 16.67 Hz , while the available grid frequency is 50 Hz . A 3-phase synchronous motor connected to the $50 \mathrm{~Hz}, 3$-phase grid, driving a synchronous generator, is used for this application.

Which one of the following combinations is a suitable choice for the number of poles in the motor and generator, respectively?

Which one of the following options is correct regarding the typical double-squirrel-cage structure used in induction motors?

The figure shows the single-line diagram of a synchronous generator delivering $\mathrm{P}=50 \mathrm{MW}$ of power at unity power factor to an infinite bus.

$I_s$ denotes the stator current phasor. If the field excitation is increased, which one of the following options correctly describes its effect on the stator current, power factor, and load angle of the machine?

A $220 \mathrm{~V} / 12 \mathrm{~V}$ single-phase transformer is designed for use in India and rated 100 VA at 50 Hz . Later, this unit is shipped to the USA where it is used as a $110 \mathrm{~V} / 6 \mathrm{~V}$ transformer at 60 Hz . Which of the following statements is/are correct?