ABB Placement Paper (Technical)(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)noneaccording to our conclusion answer will be none because if we apply two frequency component resultant 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.
Ans:- 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.....
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.
6.which table is referred for sag calculation-
Ans:- stringing
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
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)
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
Ans:- more than BJT
17. Remember truth table of AND, NOR, NAND, OR, EX-OR ETC...18. What is Truth Table Explain?
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)
23. Improvement in power factor reduces
(a) power consumed by consumer, (b) power generation, (c) both a & b Ans: (c)
24. Read about field test of Series Motor25. No-load test for Synchronous motor, the graph is drawn
Ans:- 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. Ans: (a)
27. Insulation used in transformer ___________leakage flux.
(a) increases, (b) decreases. Ans: (b)
28.After rain what happens to Insulator(a) break-down strength of Insulator decreases, (b) Arch length reduces Ans: (b)
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 Ans: (a)
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 beAns:- Vm sin (-20)
32. In a particular ckt I = Im Sin (wt -270) and V = Vm Sin wt, then type of ckt isAns:- pure resistive ckt
33. In a L-R ckt energy lost = 2000 W, energy conserved = 500W, then what is the time constant?Ans: time constant = L/R = 0.5
34. In electro-dynamometer A' meter & wattmeter the type of scale is
Ans: Non-uniform
35. For the same current carrying capacity corona loss of ACSR will be ________than copper conductor.(a) more, (b) less, (c) equal. Ans:(b)
36. A R-C ckt , supplied with DC, a bulb is connected across the Capacitor, then what happens to the illumination, if we change the capacitance.
Ans: No change at all
37. Read about surge impendence of over-head and under-ground cable, Surge impedence formula = sqrt(L/C)
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with warm regards
Harish Sati
Indira Gandhi National Open University (IGNOU)
Maidan Garhi, New Delhi-110068
(M) + 91 - 9990646343 | (E-mail) Harish.sati@gmail.com
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