131. Two-reaction phasor diagram of a salient-pole synchronous generator is considered, where
     I_a = armature current per phase,
     X₁ = armature leakage reactance per phase,
     X_d = direct axis synchronous reactance,
     X_q = quadrature-axis synchronous reactance, and
     V = generator terminal voltage, taken as reference.
     The voltage in-phase with the direct-axis will be phasor-sum of

1. 1. V + I_α r_α + I_α X₁

   
   
   

   2. V + I_α r_α + I_α X_d

   
   
   

   3. V + I_α r_α + I_α X_q

   
   
   

   4. V + I_α r_α + I_q (X_d + X_q)

   
   
   

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   NA

   Correct Option: A

   NA

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132. 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. 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

   
   
   

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   NA

   Correct Option: B

   NA

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133. A synchronous motor with negligible armature resistance runs at a load angle of 20° at the rated frequency. If supply frequency is increased by 10%, keeping other parameters constant, the new load angle will be

1. 1. 16°

   
   
   

   2. 18°

   
   
   

   3. 20°

   
   
   

   4. 22°

   
   
   

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   NA

   Correct Option: B

   NA

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134. The speed of an induction motor is controlled by varying supply frequency keeping V/f constant breakdown torque

1. 1. and magnetizing current would both remain constant

   
   
   

   2. would remain constant but magnetizing current would increase

   
   
   

   3. would decrease but magnetizing current would remain constant

   
   
   

   4. and magnetizing current would both decrease.

   
   
   

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   NA

   Correct Option: A

   NA

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135. Assume that startor impedance of an induction motor is negligible. The frequency of voltage applied to the motor is increased keeping V/f constant. The maximum motor torque will

1. 1. increase and will occur at smaller values of slip

   
   
   

   2. increases and will occur at larger values of slip

   
   
   

   3. remain constant but will occur at smaller values of slip

   
   
   

   4. remains constant but will occur at larger values of slip

   
   
   

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   NA

   Correct Option: C

   NA

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