Abb Placement Papers

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 resultant frequency we can not say with such an ease. You 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 Ô, Ô is
(a) Avg value, (b) Rms value, (c) Maximum value.....................Ans:
(a)...[confirm it]

15. Voltage & current in a ckt is given by V= V1+j V2 and I= I1 +j I2, then rms power is
.......(refer book by Edministrator on NETWORK ..)

16. Input impedence of MOSFET is
(a) more than BJT........(Ans)

17, 18. Remember truth table of AND, NOR, NAND, OR, EX-OR ETC...

19. Conversion of Binary number into Equivalent decimal No.

20. Megger is used for the measurement of (a) Insulation resistance, (b)
Conductor resistance.............Ans: (a)

21. Form factor for sinusoidal as well as DC

22. Formulae of Regulation (Vs- Vr)* 100/ Vr, then transmission line is
(a) short transmission line, (b) long, (c) medium...................Ans: (a)