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Question 7.11: The reactances Xd and xq of a salient-pole synchronous gener......

The reactances {\boldsymbol{x}}_{d} and x_{\boldsymbol{q}} of a salient-pole synchronous generator are 0.95 and 0.7 p.u., respectively. The armature resistance is negligible. The generator delivers rated kVA at unity PF and rated terminal voltage. Calculate the excitation voltage.

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We apply

E_{f}^{\prime}=V_{t}+j I_{a}x_{q}

As a result,

E_{f}^{\prime}=1+j(1)(0.7)=1.22\angle34.99\;\mathrm{deg}

We now have

\begin{array}{c}{{I_{d}=I_{a}\sin34.99~\mathrm{deg}}}\\ {{=0.57~\mathrm{p.u.}}}\end{array}

We can thus compute

\begin{array}{c}{{|E_{f}|=|E_{f}^{\prime}|+|I_{d}(x_{d}-x_{q})|}}\\ {{=1.22+0.57(0.25)}}\\ {{\delta=34.99\;\mathrm{deg}}}\end{array}

Figure 7.32 pertains to this example.

7.32

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