ABB Test Paper :2

 ABB>> Test Paper :2         This ABB Paper is viewed by 21074 times      Company List
  

Test Paper :2
 Paper Type     : Whole Testpaper  Test Date        : 2  May  2004   Posted By        : Admin  ABB VADODRA PAPER 2 MAY,2004

TECHNICAL PAPER-40 QUESTION, 45- MINUTES 

(1)in a ckt. We r giving voltage of 50 Hz as well as 60. then what will be  the resultant frequency. 
(a)less than 50 (b)more than 60(c)in between 50 & 60 
(d)none..........according to our conclusion answer will be none because if  we apply two frequency component resultatnt frequency we can not say with  such an ease.U should confirm the answer 

2.In a ckt a single resistor is connected across a d.c. source, what will be  the effect on current in first resistor if we connect one more resistance in  parallel with earlier one.... 
Answer.. no change since it is a parallel combination. 

3.why we don,t like flashover in transmission line (t-line)-  (a ) it may create earth fault(b )it reduces the life of insulator..... 
Read something about flashover & puncture. 

4.total no of strands in a acsr conductor is 81, then what is the no. of  conductor in its outer layer....(a)36 (b)18 (c)24.......Also read some more  on acsr. 

5.Two questions based on p.u. calculation like , p.u. calculation is given  with respect to some old base and u have to calculate it with reference to  new base.  (new resistance/old)=(mva new /mva old)*(old voltage/new voltage)2. 

Other question is based upon transfer of p.u calculation in transformer i.e.  how base changes when we we move from primary to secondary or like wise.read  some more on p.u calculation. 

6.which table is referred for sag calculation- 
(a)stringing chart......answer 

7.in a R-L ckt a ac voltage is applied , such that instantaneous power is  negative for 2ms, then what will be the power factor. 
(a) 9 deg, (b) 18 deg, (c) 36 Deg...........(I don't know the correct ans) 

8. In an incandescent lamp 
(a) luminous intensity is more than non-luminous intensity 
(b) ,, ,, ,, less ,, ,, ,, 

Ans: Since efficiency is less than 100%, hence ans is (b), u should confirm 
it further. 

9. In which motor no-load to full-load diff. is lowest 
(a) series motor, (b) shunt motor, (c) Compound motor 
Ans: (b) 

10. In a 60Hz induction motor full load speed is 850 rpm then what is the  Synchronous speed. (a) 900 rpm, (b) 950 rpm, (c) 1600 
rpm....................Ans: (a) 

11. A sync. Motor is running at synch. Speed, if al of sudden D.C.  excitation is removed, then 
(a) it will rotate at slip speed, (b) it will stop, (c) it will continue to  rotate at sync. Speed 
Ans: (a), because actually it will acts as Induction motor. 

12. A transmission line is designed for 50Hz, 440KV. If we want to transfer  power at 60Hz, 440 KV, then the power transfer capability will 
(a) decrease, (b) Increase, (c)None 
Ans: (a) ...as P=( |Vt| |Ef| sin (delta) ) / X, where (delta) is torque 
angle. 

13. Increased rotor resistance in rotor ckt of induction motor is related  with 
(a) high starting torque, (b) more speed variation,.....................Ans: 
(a) 

14. In the formulae E = 4.44 f N