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GATE 2019: Electrical Machines Quiz 4

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Question 1

Determine the value of the difference between backward and forward slip in case of a 230V, 50Hz, 4 pole single phase induction machine if synchronous speed = 2372rpm, rotor speed = 1969 rpm 
[Write the answer upto two decimal point]

Question 2

A 220 V, 50Hz, 6 – pole single phase induction motor is running at a speed of 940 rpm in clockwise (forward) direction. If the rotor resistance at standstill is 5Ω. Then the slip of the rotor with respect to backword field is –

Question 3

A single-phase, 230 V, 50 Hz, 4 poles, capacitor-start induction motor has the following stand still impedances
Main winding Zm = 6.0 + j4.0 Ω
Auxiliary winding Za = 8.0 + j6.0 Ω
The value of the starting capacitor  required (in μF) to produce 90o phase difference between the currents in the main and auxiliary windings will be:

Question 4

A induction motor has double-cage rotor with equivalent impedances at stand-still of (1+j1) and (0.2+j4). Find the relative values of torque produced by each cage at 5% slip.

Question 5

A single phase 60 Hz generator supplies an inductive load of 2000kW at a power factor of 0.404 lagging by means of an overhead transmission line 30 km long. The line resistance and inductance are 0.0122 ohm and 0.35 mH per km. The voltage at the receiving end is required to be kept constant at 8 kV. Find voltage regulation in Percentage (%) of the line.

Question 6

A universal motor (ac - operated) has a 2-pole armature with 960 conductors. At a certain load, the motor speed is 5000 rpm and the armature current is 4.6 A, the armature terminal voltage and input power are respectively 100 V and 300 W. Calculate the effective armature reactance in ohm assuming on armature resistance of 3.5 Ω.
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Jun 15ESE & GATE EE