Latest ABB Placement Papers

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 Administrator 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)

23. Improvement in power factor reduces

(a) power consumed by consumer, (b) power generation, (c) both a & b...........Ans: (c) [Confirm it]

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.......................................(Ans: a)

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)..[Confirm it]

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 be (a) Vm sin (-20) Ans:(a)

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...........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)

[N.B] We are not mentioning the options in sequence, and do not think that ans for the most questions is option (a). Read all options very carefully as all are very close to each other.

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