Question

A salient pole synchronous motor having $X_d=1.5p.u$ and $X_q=1p.u$ is synchronized to infinite bus bar. If excitation is reduced to zero, then maximum p.u. power it can deliver without losing synchronization is ________.

• A. 0.166

Answer 1

The correct option is A 0.166
If E(excitation) is zero, reluctance power is

$P_{(p.u)}=\frac{V_t^2}{2}\left(\frac{X_d-X_q}{X_d\times X_q}\right).\sin 2\delta$

P is maximum when, $2\delta ={90}^0$

$\delta ={45}^0$

$P_{max}=\frac{1^2}{2}\left(\frac{1.5-1}{1.5\times 1}\right)=0.16666p.u$