If the star side of the star-delta transformer shown in the figure is excited by a negative sequence voltage, then
- $V_{AB}$ leads $V_{ab}$ by $60^\circ$
- $V_{AB}$ lags $V_{ab}$ by $60^\circ$
- $V_{AB}$ leads $V_{ab}$ by $30^\circ$
- $V_{AB}$ lags $V_{ab}$ by $30^\circ$