The min-terms of a four variable Boolean function Y is given by  

Use Karnaugh map to minimize the function Y. Realize function Y employing only three-input NAND gates.

A set of three linear equations with unknowns X, Y and Z is shown below

Decompose the coefficient matrix into an upper triangular matrix and then solve for the unknowns, X, Y and Z.

The convolution of the functions  and   is equal to _________.

An inverter capable of supplying a balanced three-phase variable voltage variable frequency output is feeding a three-phase induction motor rated for 50Hz and 440V. The stator winding resistances of the motor are negligible small. During starting, the current inrush can be avoided without sacrificing the starting torque by suitably applying:

In order to have a lower cost of electrical energy generation,

For a J-K flip-flop its J input is tied to its own  output and its K input is connected to its own Q output. If the flip-flop is fed with a clock of frequency 1MHz, its Q output frequency will be _________________

A single phase inverter with square wave voltage will have in its output waveform a fifth harmonic component equal to ____________________ percentage of the fundamental.

Fringing in a capacitance type transducer can be minimized by providing a

For the circuit shown in figure, find the current through the resistance R connected between points a and b by Thevenin’s theorem.

The RMS value of the periodic waveform S(t), shown in figure is:

A certain oscilloscope with 4 cm by 4 cm screen has its own sweep output fed to its input. If the x and y sensitivities are same, the oscilloscope will display a  

A Kelvin double bridge is best suited for the measurement of

Match the output wave forms:

(P) Single phase fully controlled ac-dc converter

(Q) Voltage commutated dc-ac chopper (E=input dc Voltage)

(R) Phase voltage of a star connected balanced three-phase load fed from a three-phase inverter with 180° Conduction. (input dc voltage=E)

(S) Line voltage of a six stepped inverter with input dc voltage E

(T) Three-phase diode bridge rectifier

(A)

(B)

(C)

(D)

(E)

A dc to dc transistor chopper supplied from a fixed voltage dc source feeds a fixed resistive-inductive load and a free-wheeling diode. The chopper operates at 1 kHz and 50% duty cycle. Without changing the value of the average dc current through the load, if it is desired to reduce the ripple content of load current, the control action needed will be:

An oscilloscope is operated in the X-Y mode. The figure 8 is displayed on the oscilloscope screen. If the frequency of the X-input is 1 kHz, the Y-input frequency is _____________________.

Match the following 

Type of bridge                                       Application

(a) Wien bridge                                      (P) Measurement of resistance

(b) Maxwell bridge                               (Q) Medium Q inductors

(c) Scherring bridge                             (R) Measurement of frequency

(d) Anderson bridge                             (S) High voltage capacitors

(e) Blumlein bridge                               (T) Low Q inductors

                                                                 (U) Insensitive to stray electrostatic fields

The positive sequence component of the voltage at the point of fault in a power system is zero for a 3 – phase fault. (True=1/False=0)

Closed loop stability implies that  has only Zeros in the left half of the s-plane. (True=1, False=0)

A loss-alternator supplies 50 MW to an infinite bus, the steady state stability limit being 100MW. Determine if the alternator will remain stable if the input to the prime mover of the alternator is abruptly increased by 40 MW.
(Yes=1/No=0)

In load-flow analysis, a voltage-controlled bus is treated as a load bus in subsequent iterations if a reactive power limit is violated. (True=1/False=0)

A system is described by the state equation. The output is given by Y=CX  

Where . Transfer function G(s) of the system is :

A three phase star-connected alternator is rated 30 MVA, 13.8 kV and has the following sequence reactance values:  

The neutral of the alternator is solidly grounded. Determine the alternator line currents when a double line-to-ground fault occurs on its terminals. Assume that the alternator is unloaded and is operating at rated voltage when the fault occurs.

Consider the chopper circuit of figure. The chopper operates at 400Hz and 50% duty cycle. The load current remains almost ripple free at 10A. Assuming the input voltage to be 200V and the devices to be ideal, the turn-off time available to the thyristor ThM is ____ μs.

A single phase diode bridge rectifier supplies a highly inductive load. The load current can be assumed to be ripple free. The ac supply side current waveform will be:

The inverse of the matrix  is:

In an 8085 microprocessor, after the execution of XRA A instruction  

For the circuit shown in figure, the transfer function is equal to ?

The impulse response of an initially relaxed linear system is . To produce a response of , the input must be equal to         

The characteristic equation for a certain feedback control system is given by    

The state equation of a linear time-invariant system is given by

(i) Find state transition
(ii) Determine the state vector for t=0 when r(t)=U(t). Assume values of states initially to be zero.

Given the matrix. Its Eigen values are ____________.

A subroutine PROG1 written in the 8085 assembly language is given below. At entry to this program, the values of different registers in HEX are. A=05; BC=0000; DE=5472; HL=4528, All the flags are set to 1. Determine the register contents and condition of the zero and carry flags after the execution of the program. (i.e., after executing RET statement). What does the program accomplish?

PROG1        MOV A, E

        ADD L

        DAA

        MOV L, A

        MOV A, D

        ADC H

        DAA

        MOV H, A

        MVI A, 00H

        RAL

        RET

The closed loop transfer function of a control system is given by

For a unit step input the output is

The block diagram of the control system is given in the figure.  

A spherical conductor of radius ‘a’ with charge ‘q’ is placed concentrically inside an uncharged and unearthed spherical conducting shell of inner and outer radii  respectively. Taking potential to be zero at infinity, the potential at any point P within the shell  will be:        

A monochromatic plane electromagnetic wave travels in vacuum in the positive X direction (x, y, z system of coordinates). The electric and magnetic fields can be expressed as

A three phase ac-to-dc diode bridge rectifier is supplied from a three-phase, 440V source. The rectifier supplies a purely resistive load. The average dc voltage across the load will be ________________V.

A  digit, 2 V full scale slope ADC has its integration time set to 300ms. If the input to the ADC is (1+1sin314t)V, then the ADC output will be

If the inductance and capacitance of a power system network upto a circuit breaker location are 1H and 0.01μF respectively, the value of the shunt resistor across the circuit breaker, required for critical damping of the re-striking voltage is _________________

Figure, show two thyristors each rated 500A (continuous) sharing a load current. Current through thyristor Y is 120A. The current through thyristor X will be nearly ______________ A.

The single phase half controlled ac to dc bridge converter of figure supplies a 10 Ohm resistor in series with a 100V back emf load. The firing angle of the thyristors is set to 60°

(i) Find the average current through the resistor

(ii) What will be the new average current through the resistor, if a very large inductor is connected in series with the load?

The distance relay with inherent directional property is known as ________________  relay.

A steady current I flows through a long cylindrical wire of radius R. find the magnetic vector potential at any point outside the conductor at radius. Vector potential on the surface of the conductor may be taken to be equal to zero.

The Laplace transform of f(t) is F(s). Given , the final value of f(t) is :

A series R-L-C circuit has the following parameter values: , , .The Q factor of the circuit at resonance is __________

In the network system shown in figure, find the current through  using nodal method. The values of voltages are given in volts and the impedances are given in ohms.

Consider the thyristor circuit of figure. The Thyristor is given a triggering pulse after every 10ms. Calculate the duration for which the thyristor remains ON after each triggering pulse. Assume ideal devices and explain briefly the basis.

Figure below, shows the details of an electromagnet with an operating coil rated for 230V, 50 Hz. The coil has 1500 turns. Find the average force of attraction on the armature of the electromagnet and the current drawn by the coil. Omit winding resistance and core losses and assume infinite permeability for the core.

The steady state error due to a step input for type 1 system is _______________

Four ammeters, M1, M2, M3 and M4 with the following specifications are available.

A current of 1A is to be measured. To obtain minimum error in the reading, one should select meter

Match the following

A three-phase delta-wye connected 30MVA, 33 kV/11 kV transformers is protected by a simple differential relaying scheme. The CT ratio on the primary side is 500: 5 and that on the secondary side is 2000: 5. Sketch the CT connection diagram for the relaying scheme. Also calculate the relay current setting for faults drawing upto 200% of the rated current.

An induction motor is fed from a balanced three phase supply at rated voltage and frequency through a bank of three single phase transformers connected in delta-delta. One unit of the bank develops fault and is removed. Then,

Root locations of the characteristic unit step responses of second order of second equations order systems        

A synchronous motor on load draws a current at a leading power factor angle . If the internal power factor angle- which is the phase angle between the excitation e.m.f. and current in the time phasor diagram is  then the air gap excitation m.m.f lags the armature m.m.f by

In the circuit of figure, ammeter  reads 12A and  reads 9A. will read ________________A.  

The common mode voltage of a unity gain (voltage follower) op-amp buffer in terms of its output voltage   is . ( True=1, False=0)

A differentially compounded d.c. motor with inter poles and with brushes on the neutral axis is to be driven as a generator in the same direction with the same polarity of the terminal voltage. It will then

Supply to one terminal of a delta-wye connected three-phase core type transformer which is on no-load, fails. Assuming magnetic circuit symmetry, voltages on the secondary side will be:

For the circuit shown in figure, determine  and hence write the equations for the magnitude and phase response of . If the value of  is 100k Ohm and of R is 10k Ohm, determine the value of C to obtain a phase shift to 270° between  and  for an input frequency of 1000rad/s.

A 220V, 1.5 kW, 859 rpm, separately excited dc motor has armature resistance of 2.5 ohms and it draws a current of 8A at rated-load condition. If the field current and the armature voltage are fixed at the value of rated speed at rated load, what will be the no-load speed of the motor? Assume losses remain constant between no-load and full load operation.

When started by means of an auto-transformer with 50% tapping, supply current at start of an induction motor is reduced to ______________ of that when started by means of a star-delta starter.

An induction motor runs stably under constant torque load at 1250 rpm off a 50Hz supply. Its number of poles is _______________

Two 100V full scale PMMC type dc voltmeters having figure of merits (FOM) of 10kΩ/V and 20kΩ/V are connected in series. The series combination can be used to measure a maximum dc voltage of _____________________V.

The distribution factor for a 36 slot stator with three-phase, 8-pole winding, having 120° phase spread, is _____________

The percentage impedance of a 100 kVA, 11 kV/400V, delta/wye, 50Hz transformer is 4.5%. For the circulation of half the full load current during short circuit test, with low voltage terminals shorted, the applied voltage on the high voltage side will be ________.         

A three-phase, 50Hz, 415V, synchronous machine operates at rated voltage and at a leading power factor of 0.8. Shaft power is 15 kW and excitation emf is 400V. If per phase resistance is 0.5 ohm, find the synchronous reactance. Neglect mechanical losses of the system.

Motor characteristics         

(a) Speed torque characteristics of induction machine under motoring operation.

(b) Current torque characteristics of a dc series motor

(c) Power factor variation with voltage of an induction motor under no-load operation

(d) Speed torque characteristics of induction machine under dc injection dynamic braking operation

(e) Speed torque characteristics of dc series motor.

For the circuit shown in figure, determine the input impedance Z. assume the op-amp to be an ideal one.

A symmetrical star connected three-phase load is made of three identical coils having an internal resistance of 12 Ohm and inductance of 142mH. The power taken by this load when connected to a balanced three-phase three-wire supply of 400V, 50Hz is measured using the two wattmeter method. The watt meters used are similar and are of type of 400V, 5A, UPF, class 1 accuracy.

A 50 Hz, 440V, three-phase, 4-pole induction motor develops half the rated torque at 1490rpm. With the applied voltage magnitude remaining at the rated value. What should be its frequency if the motor has to develop the same torque at 1600rpm? Neglect stator and rotor winding resistances, leakage reactances and iron losses.

The surge impedance of a 400 km long overhead transmission line is 400 ohms. For a 200 km length of the same line, the surge impedance will be:

A 4 kVA, 50 Hz, single-phase transformer has a ratio 200/400V. the data taken on the l.v. side at the rated voltage show that the open circuit input wattage is 80W. The mutual inductance between the primary and the secondary windings is 1.91H. What value will be the current taken by the transformer, if the no-load test is conducted on the h.v. side at rated voltage? Neglect the effect of winding resistance and leakage reactances.

The insulation level of a 400 kV EHV overhead transmission line is decided on the basis of

The main criterion for selection of the size of a distribution for a radial distribution system is:

The insulation resistance of a cable of length 10 km is 1 MΩ. For a length of 100 km of the same cable, the insulation resistance will be

The rated load of an underground cable is always greater than its natural load.  (True=1/False=0)

Two identical three-phase transmission lines are connected in parallel to supply a total load of 100 MW at 132 kV and 0.8p.f lagging at the receiving end. The ABCD constants of each transmission line are as follows:        

;

Determine:

(a) The ABCD constants of the combined network.

(b) The sending-end power factor  

In a string of three identical suspension insulator units supporting a transmission line conductor, if the self capacitance of each unit is denoted as C Farads, the capacitance of each connector pin to ground can be taken as 0.1 C Farads. Determine the voltage distribution across the string if the maximum permissible voltage per unit is given as 20kV. Also determine the string efficiency.