Company: Abb Technologies
NO. OF QUESTIONS : 40
TIME: 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
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….
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 tosecondary or like wise.read some more on p.u calculation.
6.which table is referred for sag calculation-
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 ,, ,, ,,
9. In which motor no-load to full-load diff. is lowest
(a) series motor, (b) shunt motor, (c) Compound motor
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) 1600rpm…
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
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
13. Increased rotor resistance in rotor ckt of induction motor is related with
(a) high starting torque, (b) more speed variation,
14. In the formulae E = 4.44 f N ?, ? is
(a) Avg value, (b) Rms value, (c) Maximum value
15. Voltage & current in a ckt is given by V= V1+j V2 and I= I1 +j I2, then rms power is…
16. Input impedence of MOSFET is
(a) more than BJT
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
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
23. Improvement in power factor reduces
(a) power consumed by consumer, (b) power generation, (c) both a & b
24. Read about field test of Series Motor…
25. No-load test for Synchronous motor, the graph is drawn
(a) stator open ckt emf Vs field current
26. An AC voltage of 50Hz is impressed in a resistive ckt, the oscillating power has a frequency
(a) 50 Hz, (b) 100, (c) no oscillating power is there in resistive ckt
27. Insulation used in transformer ___________leakage flux.
(a) increases, (b) decreases
28.After rain what happens to Insulator
(a) break-down strength of Insulator decreases, (b)Arch length reduces
29.Diversity factor helps to …………(what ?) [Read diversity factor, load factor, Reserve capacity factor in depth, with calculation]
30. Why capacitance is shown as a Shunt element in analysis of transmission line
(a) it is between Conductor & earth, (b) because Admittance is used for calculation of capacitive reactance
31. B-R-Y sequence is followed in three phase system, if phase voltage in B-phase is Vm sin 100, then the phase voltage in R-phase would be
(a) Vm sin (-20)
32. In a particular ckt I = Im Sin (wt -270) and V = Vm Sin wt, then type of ckt is (a) pure resistive ckt
33. In a L-R ckt energy lost = 2000 W, energy conserved = 500W, then what is the time constant
34. In electro-dynamometer A,meter & wattmeter the type of scale is
35. For the same current carrying capacity corona loss of ACSR will be ________than copper conductor.
(a) more, (b) less, (c) equal. Ans: (b)