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GATE 2019: Electrical Machines Quiz 8 (App update required to attempt this test)

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Question 1

A 230V, 20 hp, 60 Hz, 6-pole, 3-phase induction motor driving a constant torque load at rated frequency, rated voltage and rated horse-power, has a speed of 1175 rpm and an efficiency of 92.1%. Determine the new operating speed if a system disturbance causes 10% drop in voltage and 6% drop in frequency. Assume that friction, windage and stray power losses remain constant.

Question 2

A non-salient pole synchronous generator having synchronous reactance of 0.8 pu is supplying 1 pu power to a unity power factor load at a terminal voltage of 1.1 pu. Neglecting the armature resistance, the angle of the voltage behind the synchronous reactance with respect to the angle of the terminal voltage in degrees is ________.

Question 3

A single phase two winding transformer shown below in (fig-1) is reconnected as an autotransformer shown in (fig-2.) If the connection of 200V winding are reversed as shown in (fig-3.) What is value of V1 required to be applied across terminal X2 and H2 to obtain the same 800V output?

Question 4

The per phase equivalent of a synchronous generator feeding a synchronous motor through a transmission line is shown in figure below.


Each machine is rated 10 KVA,400 V 50 Hz. The motor is driving a load of 8 kW. The field current of the two machines are so adjusted that the motor terminal voltage is 400 V and its pf.is 0.8 leading. Determine the magnitude of Eand Em

Question 5

The steam input in to a turbo generator connected to infinite bus is increased. Which of the events will take place?

Question 6

The incremental cost characteristics of two generators delivering 200 MW are as follows
 
For economic operation, the generations P1 and P2 should be
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Jun 18ESE & GATE EE