A synchronous motor is running from an infinite bus of voltage

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A synchronous motor is running from an infinite bus of voltage V₁ in steady-state, at about 50% of its rated load with a power-angle δ₁ between V_t and E_f (induced voltage). The load is suddenly decreased to 25%. E_f attains its new steady-state power angle δ₂ with V_t by initially

1. falling behind and making a complete rotation
2. advancing and making a complete rotation
3. falling behind, followed by oscillation about δ₂
4. advancing, followed by oscillation about δ₂

Correct Option: B

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