Question

The full load torque angle of a synchronous motor at rated voltage and frequency is ${30}^{\circ }$electrical. The stator resistance is negligible. The torque angle if load torque and terminal voltage are kept constant and excitation and frequency are increased by 10% is _____elec.degrees.

• A. 33.36

Answer 1

The correct option is A 33.36
$P_m=\frac{V_t{E}_f}{X_d}\sin \delta =\frac{V_t{E}_f}{X_d}\sin {30}^{\circ }$

$T_m=\frac{V_t{E}_f}{{\omega }_s{X}_d}\sin {30}^{\circ }$

$T_m=\frac{V_t\times 1.1E_f}{1.1{\omega }_s\times 1.1X_d}\sin \delta =\frac{V_t{E}_f}{{\omega }_s{X}_d}\sin {30}^{\circ }$

$\Rightarrow sin\delta =1.1\sin {30}^o$

$\delta ={\sin }^{-1}\left(0.55\right)$

$\delta ={33.36}^o$