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What is the unsaturated synchronous reactance (Xm) in an alternator if the armature resistance is neglected according to the following graph? 

F1 Eng Arbaz 17-1-24 D9

This question was previously asked in
SSC JE Electrical 4 Dec 2023 Official Paper II
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  1. Xsu = Ead / Iab
  2. Xsu = Ead Iab
  3. Xsu = Ra + jZsu
  4. Xsu = I / (Ra + jXsu)

Answer (Detailed Solution Below)

Option 1 : Xsu = Ead / Iab
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Explanation:
The unsaturated synchronous reactance (Xm) in the alternator is equal to the ratio of length of "ad" and the ab.
In general for, it is equal to the ratio of voltage Ead and current Iab.

Xsu = Ead / Iab

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Q1. The synchronising torque TSY of an alternator connected to an infinite busbar is given by: (Where E is the generated EMF, XS is the synchronous reactance, α is the slot angle and NS is the synchronous speed)
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More Alternator and Synchronous Motors Questions

Q1.Which statements about voltage drop in an alternator are correct? I. The voltage drop due to armature resistance (IaRa) is in phase with the armature current (Ia). II. At unity power factor, the voltage drop IaRa directly subtracts from the generated EMF (E). III. For a leading power factor load, IaRa contributes to an increase in terminal voltage (V). IV. Armature resistance has no effect on voltage regulation.
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Q7.Which statements about the maximum power output of a cylindrical rotor synchronous generator are correct? I. Maximum power output occurs when the load angle (δ) is 90°. II. Maximum power is proportional to the square of the terminal voltage (V). III. Over-excitation increases the generator’s maximum power capability. IV. Maximum power is independent of the synchronous reactance (Xs).
Q8.Stray load losses in synchronous motors are caused by __________. 
Q9.In a synchronous motor, If the load angle exceeds 90°, then the motor will: 
Q10.Why are short-pitch windings preferred in alternators despite their lower induced EMF per coil?
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Q1.If a 6-pole induction motor operates on a 60 Hz supply, its synchronous speed is _____________.
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