Two transformers are to be operated in parallel such that they share load in proportion to their kVA ratings. The rating of the first transformer is 500 kVA and its pu leakage impedance is 0.05 pu. If the rating of second transformer is 250 kVA, then its pu leakage impedance is

1.  0.20

2.  0.10

3.  0.05

4.  0.025

View Answer  
4
Correct Answer :

0.10


Explanation :
No Explanation available for this question

The speed of a 4-pole induction motor is controlled by varying the supply frequency while maintaining the ratio of supply voltage to supply frequency (V/f) constant. At rated frequency of 50 Hz and rated voltage of 400 V its speed is 1440 rpm. Find the speed at 30 Hz, if the load torque is constant.

1.  882 rpm

2.  864 rpm

3.  840 rpm

4.  828 rpm

View Answer  
4
Correct Answer :

864 rpm


Explanation :
No Explanation available for this question

The speed of a 4-pole induction motor is controlled by varying the supply frequency while maintaining the ratio of supply voltage to supply frequency (V/f) constant.At rated frequency of 50 Hz and rated voltage of 400 V its speed is 1440 rpm.Find the speed at 30 Hz, if the load torque is constant.

1.  882 rpm

2.  864 rpm  

3.  840 rpm  

4.  828 rpm

View Answer  
4
Correct Answer :

864 rpm

 


Explanation :
No Explanation available for this question

A 3 phase,10 kW,400 V,4 pole,50 Hz star connected induction motor draws 20 A on full load. Its no load and blocked rotor test data are given below: No Load test:400W 6A 1002W Blocked Rotor test:90V 15A 762W Neglecting copper loss in no Load test and core loss in Blocked Rotor test, estimate motor's full load efficiency.        

1.  76 %

2.  81%    

3.   82.4 %    

4.  85%

View Answer  
4
Correct Answer :

81\%

 

 


Explanation :
No Explanation available for this question

A 3 phase, 400 V, 5 kW, star connected synchronous motor having an internal reactance of 10 is operating at 50% load,unity pf. Now,the excitation is increased by 1%. What will be the new load in percent,if the power factor is to be kept same?Neglect all losses and consider linear magnetic circuit

1.  67.9%

2.  56.9%

3.  51%  

4.  50%

View Answer  
4
Correct Answer :

67.9\%


Explanation :
No Explanation available for this question

the A,B,C,D constants of a 220 kv line are:A=D=0.94π if the sending end voltage of the line for a given load delivered at normal voltage is 240 kv,then  % of voltage regulation of the line is

1.  5

2.  9%

3.  16  

4.  21

View Answer  
4
Correct Answer :

16

 


Explanation :
No Explanation available for this question

A single phase transmission line and a telephone line are both symmetrically strung one below the other, in horizontal configurations, on a common tower. The shortest and longest distances between the phase and telephone conductors are 2.5 m and 3 m respectively. The voltage (volt/km) induced in the telephone circuit, due to 50 Hz current of 100 amps in the power circuit is    

1.  4.81

2.  3.56  

3.  2.29  

4.  1.27

View Answer  
4
Correct Answer :

2.29

 


Explanation :
No Explanation available for this question

Three identical star connected resistors of 1.0 pu are connected to an unbalanced 3 phase supply. The load neutral is isolated. The symmetrical components of the line voltages in pu are: Vab1 = X θ1, Vab2 = Y θ2. If all the pu calculations are with the respective base values, the phase to neutral sequence voltages are

1.  Van1 = X (θ1 + 30°), Van2 =Y (θ2 - 30°)  

2.  Van1 = X  (θ1 - 30°), Van2 = Y  (θ2 + 30°)

3.  Van1 = 1/√(3) X (θ1 - 30°), Van2 = 1/√(3) Y (θ2 - 30°)

4.  Van1 = 1/√(3) X  (θ1 - 60°), Van2 = 1/√(3) Y  (θ2 - 60°)

View Answer  
4
Correct Answer :

Van1 = 1/√(3) X (θ1 - 30°),

Van2 = 1/√(3) Y (θ2 - 30°)


Explanation :
No Explanation available for this question

A generator is connected through a 20 MVA, 13.8/138 kV step down transformer, to a transmission line. At the receiving end of the line a load is supplied through a step down transformer of 10 MVA, 138/69 kV rating. A 0.72 pu load, evaluated on load side transformer ratings as base values, is supplied from the above system. For system base values of 10 MVA and 69 k V in load circuit, the value of the load (in per unit) in generator circuit will be      

1.  36

2.  1.44  

3.  0.72  

4.  0.18

View Answer  
4
Correct Answer :

36


Explanation :
No Explanation available for this question

The Gauss Seidel load flow method has following disadvantages.Tick the incorrect statement

1.  Unreliable convergence

2.  Slow convergence  

3.  Choice of slack bus affects convergence  

4.  A good initial guess for voltages is essential for convergence

View Answer  
4
Correct Answer :

A good initial guess for voltages is essential for convergence


Explanation :
No Explanation available for this question
Previous Next

Interview Questions

MongoDB
Java Script
Node JS
PHP
JQuery
Python