Question

The V curve of an alternator is as shown in figure for rated armature current $I_a$ of the machine is

• A. more stable at P
• B. equal stable at P and Q
• C. not stable at P and Q
• D. more stable at Q

Answer 1

The correct option is D more stable at Q

$P_{sy}=\frac{EV}{X_s}cos\delta$

$\text{where}{P}_{sy}=\text{symmetrical power coefficient}$

$P_{sy}\propto \text{stability}\propto \text{excitation}$

$\text{at 'Q' the excitation is more than at 'P'.}$

$\text{So it is more stable at Q.}$