Question

A salient pole alternator has $X_d=1.5p.u.,X_q=0.80p.u.$ If this alternator is supplying rated kVA at unity power factor to infinite bus and infinite bus voltage is 1.0 p.u., then power angle will be

• A. ${19.25}^{\circ }$
• B. ${38.65}^{\circ }$
• C. ${30.25}^{\circ }$
• D. ${50.13}^{\circ }$

Answer 1

The correct option is B ${38.65}^{\circ }$

Power angle can be calculated as,
$\overrightarrow{E_f^{\prime }}=\overrightarrow{V_t}+j\overrightarrow{I_a}{X}_q$

As rated load is being supplied at unity power factor,
$\therefore$ $\overrightarrow{I_a}=1\angle 0^{\circ }p.u.$

$\overrightarrow{E_f^{\prime }}=1.0\angle 0^{\circ }+j1.0\angle 0^{\circ }\left(0.8\right)$
$=1.28\angle {38.65}^{\circ }p.u.$

$\therefore$ $\text{Power angle,}\delta ={38.65}^{\circ }$