Jegadesh sankar

Miles to go before i sleep

Q&A for Electrical Engineers

Actually these questions are given as Question bank for our Comprehension exam. This was handleed by Prof B.L Mathur and prof M.C.Vaithiyalingam. I tryed solving and found some answers. Then with the help of my friends Vijay venketesh, Madan and his team now i am posting this.
Note: The answers given here may be wrong. If there is any wrong entry please reply.

1.      Why lag compensation is suitable for systems having satisfactory transient response but

         unsatisfactory steady state response?

         Lag compensation circuit is basically an integrator. Steady state response improves by integral control.

2.            An armature controlled dc servo motor , initially at rest , when energized with a step positive dc  voltage of  50V  at  time  t = 0  reaches steady state with a speed of  500rpm and exhibits a speed of 200rpm at  t = 0.3 second. What is the transfer function of the motor relating its speed in radian/second and control voltage in V? Assume first-order response for the speed of the motor.                                                                          

3.            A unity feedback control system has its forward path transfer function

         G(s)=2Kexp(-s). Determine the range of  K  which will ensure stability of the closed –loop system.

4.            A system has an infinite gain margin. Does it mean that the relative stability of the system is very high? Give reason.

         May or may not. Stability depends on both gain and phase margin

5.            Show that if we know the frequency response of a linear stable system , we can compute the dynamic response for any form of input.

6.            What is  (i) displacement current, (ii) conduction current and (iii) eddy current?

         Displacement current flows through a dielectric medium due to time varying electric field. For example charging and discharging current through a capacitor.

         Conduction current flows through a conducting medium due to steady state as well as time varying electric fields.

7.            Define electric field at a point.

         Electric field strength at any point is the negative of the potential gradient at  that point.

8.            Can a magnetic field exist in a good conductor, if the field is (i) static and (ii) time-varying?

         Static yes. Time varying no

9.      In a free space a voltage function  V is given by   V  =  x²y( z + 3 ) Volt. Find the electric

         field at the point  ( 3, 4, -6 ).

         E = -72 i    27 j  + 36 k

10.        Write down the generalized form of  Maxwell’s equations in the differential form.

         Δ . E = 1 / εo ρ         Δ . B = 0         Δ x E = -∂B / ∂t         Δ x B = μo J  +  μo εo ∂E / ∂t

11.        What is the role played by the diode in the circuit of Figure Q.11 ?

12.    How would you experimentally determine the output resistance of an amplifier?

         Keeping the input constant, connect a resistance box at the output. Adjust the resistance such that the out put voltage while the resistance is connected is half of that when the resistance is removed. Resistance of the box will be the output resistance of the amplifier

13.    Under what conditions, a sinusoidal input to an amplifier provides a sinusoidal  output

         with zero distortion?

         When the transistor operates at the Q point, the output will be sinusoidal for a sinusoidal input.

14     What are the precautions you would observe while handling a MOSFET that does not

         have any built-in protection?

         We must keep our body permanently in contact with a grounded electrode.

15.    Draw a circuit of an RC coupled transistor amplifier employing current feedback.

16.    A certain network function  F(s) has its pole-zero configuration defined by:  a zero  at

         the origin, a simple pole at ( -4 + j0 ), a pair of complex zeros at  ( -4 ± 2j ) and a pair of

         complex poles at ( 0± j5 ). If the magnitude of F(s) is  20  for infinite frequency ,

         determine  F(s).

         F(s) = { 20 s (s2 -12 +16j) } / { (s2 + 25) (s + 4) }

17.    Sketch the frequency response plots ( amplitude and phase ) of the voltage ratio transfer

         function of the two-port  RC  network shown in Figure Q.17.

         Draw the response of low pass filter

18.        The following equations describe a two-port network shown in Figure Q.18:

            V1  =  5I1  +  2I2

            V2   =  2I1  +  I2        .

         A  3-Ohm resistor is connected across the port-2. Calculate the input  impedance of the Circuit.

19.        What is a positive real function in the context of network synthesis?

20.        What are the important specifications of  a Chebyshev  low-pass filter?

21.        Write down the loop equations for the circuit shown in Figure Q.21.

22.    Determine the voltage across the 5-F capacitor in the circuit of Figure Q.21 under            steady state when  I(t) = 10A dc and  e(t) = 20V dc.

23.    Determine the voltage across the resistive load in each phase of Figure Q.23 when

         (i) the neutral of the load  is connected to  the neutral of the supply   and

         (ii) the neutral of the load is disconnected from the neutral of the supply.

         Comment on your answers.

 24.   What is the voltage across the capacitor in the circuit of Figure Q.24 under steady state?

——————————————————————————————————————

25.    Establish relation between core loss, flux and frequency.

         Core Loss consists of hysteresis loss and eddy current loss         Hysterisis loss a B1.6f  and  eddy current loss is a B2f2.

26          Establish vector relation between torque, flux and current.

27          In a separately excited D.C. generator, what percentage of power input to field circuit reaches the load connected in the armature circuit? Zero percent

28          Draw the torque speed characteristic of D.C. shunt and series motors.

29          What happens when two synchronous machines are connected in parallel without satisfying the conditions of synchronization?

         The out of phase synchronization of the generators cause a very large circulating current depending on the resistance and reactance of the machines paralleled. The heavy circulating current produces large power which can cause mechanical damage to both the shaft, bearings and especially the couplings between the prime mover and the generator as well winding damage of the generator

30          Draw the wave shape of the short circuit current of a synchronous generator. What are the different zones of this curve?

31          What is the special feature of double cage rotor induction motor?

         The outer cage has high resistance together with low reactance and the inner cage has   low resistance and a large reactance. At starting the leakage reactance of the inner cage is high enough to cause rotor current to flow in the outer cage which produces considerable I2R loss & consequently good starting torque.

32          Why single-phase induction motor is not used in kitchen grinder? Which motor is actually used?

An A.C series motor is used in the kitchen grinder. Single-phase induction motor does not have high starting torque and hence is not used.

33          Compare A.M. and F.M systems with reference to their bandwidth and immunity to noise. Why F.M is more popular for short range Trans receiver?

         FM occupies more bandwidth as compared to AM. FM is more immune to noise. For short range transmission bandwidth occupation is not as serious a matter as compared to better quality.

34          What are the merits and demerits of microwave communication over RF communication?

35          A digital code 1100101 is transmitted using phase shift keying. Draw the wave shape of the signal.

36          Why optical fibers are gaining popularity as signal transmission medium?

         These are immune to electromagnetic interference. Each fiber has a very wide bandwidth and a number of fibers can be placed in proximity in a cable permitting a large number of channels at each frequency.

37          What is a void function?

         A function which does not return anything is called a void function.

38          What are pointers?

         Pointers are special variables that contain memory addresses of other variables.

39          What is the difference between polymorphism and inheritance?

         Polymorphism is the attribute that allows one interface to control access to a general class of actions.         Inheritance is the process by which one object can acquire the properties of another object.

40          What is operator overloading?

         When an operator is defined to perform some functions in addition to its default function it is called operator overloading. For example, if + operator is defined to add two complex numbers in addition to adding two real numbers, it is overloading of + operator.

41          Let f (x)=x2,  – Π < x < Π. Without finding its Fourier series the sum

                          α

         a0 2/4 + ½ Σ an2 +bn2        

                        n=1               

          is (a) Π4/10      (b)Π4 /5         (c) Π4 /90         (d)Π4/45                 

42          The solution for the partial differential equation z = px+qy  is (a) z =ax+by

         (b) z = y f (y/x)  (c) both (a) and (b)  (d) none   

43          A rod of length l is thermally insulated at the rear end. This can be mathematically represented as: (a) 2u/2x(l, t)=0 (b) 2u/2t (l, t)=0 (c) u (l, t)=0 (d) u (0,t)=0

44           The function x e –x2/2   is self reciprocal under (a) Fourier transform (b) Fourier cosine transform (c) Fourier sine transform (d) Laplace transform.

45          The Laplace transform of te-t sin t  is (a) s2-1/(s2 +1)2 (b) s/s2  +1  (c) s/(s2 +1)2

         (d) 2 (s+1)/ [(s+1)2 +1]2  

46          The microscopic form of ohms law is (a) J=E/σ   (b) J= σE  (c) V=IR (d) J=σE2

47          In super conducting state (a) entropy increases and thermal conductivity decreases.(b) Entropy and thermal conductivity decrease. (c) Entropy and thermal conductivity increase (d) entropy decreases and thermal conductivity increases.

48          Fermi level in ‘n’ type semiconductor (a) is shifted towards lower end of

         conduction band when doping concentration increases. (b) Remains unaltered   

         when doping concentration increases. (c) Is shifted towards upper end of the   

         valence band when doping concentration increases. (d) is shifted towards lower 

         end of the conduction band when doping concentration decreases.

49          Compound semiconductor is obtained  (a) when pentavalent impurity atoms are added to tetravalent materials such as Ge, Si. (b) When trivalent impurity atoms are added to tetravalent materials such as Ge, Si. (c) When III group and V group elements are joined together using appropriate process. (d) When ‘n’ type and ‘p’ type semiconductors are joined together.

50          Ferrimagnetism arises because of unequal spin magnetic movements of ions in antiparallel configuration.

51          Which statement is correct? (a) All piezoelectric materials are dielectric (b) all dielectric materials are pyroelectric materials. (c) All dielectric materials are ferroelectric materials (d) all piezoelectric materials are ferroelectric materials.

52          Germanium and silicon are good detectors but bad light emitting sources, because (a) they are direct band gap semiconductors. (b) they are indirect band gap semiconductors (c) they are good emitters in the IR region (d) none of the above.

53          Metallic glasses make good transformer materials, because (a) of their low resistivity and low hysterisis loss  (b) of their high resistivity and low hysterisis loss (c) low resistivity and high hysterisis loss (d) high resistivity and high hysterisis loss.

 

26          Fluorescence exhibits (a) transition from meta stable level (b) after glow (c) triplet to singlet transition (d) instantaneous emission of light.

27          When an ionic crystal is heated to an elevated temperature below its melting point, the concentration point defects ion the material increases.

28          The gas constant (R) is equal to (a) sum of two specific heats (b) difference of two specific heats (c) product of two specific heats (d) ratio of two specific heats.

29          Benson boiler is a fire tube boiler. Yes/no.

30          Voltage developed to strike spark in the spark plug is in the range of (a) 6 to 12 volts (b) 1000 to2000 volts (c) 20000 to 25000 volts (d) none of the above.

31          Mechanical efficiency of reciprocating air compressor is expressed as (a) B.P/I.P

         (b) I.P/B.P (c) F.P/B.P (d) F.P/I.P.

32          Bernoulli’s equation is applicable to the following type of fluid flow (a) uniform,

          frictionless, along a streamline. (b) steady, incompressible, along a streamline. (c) steady, irrotational, uniform (d) steady, frictionless, incompressible.

33          A flow net (a) is a useful tool in checking the irrotationality of a fluid flow (b) is a

         pattern of mutually orthogonal sets of lines useful in they study of nonuniform

         flows. (c) gives a complete picture of flow pattern in unsteady flows (d) is a          geometrical construction based on ideal fluid flow theory.

34          Two pipes of diameters 0.1m and 0.2m are connected in parallel. If the head loss

         in the smaller pipe is 16m, the head loss in the other pipe is (a) 4m (b) 8m

         (c) 16m, (d) 64m.

35          A typical Pelton wheel bucket deflects the water jet through an angle of  (a) 1500 (b)1590  (c) 1700  (d) 1790 

——- ——- ——— ——————— ——————– ————————– ———–

36          Sketch an example-circuit to illustrate common mode signal and identify the common mode signal in your circuit.

         Draw differential amplifier with common input for both the transistor.

37          Mention a practical situation, which will require the employment of a notch filter and outline the reason for such a requirement.

Rejects single frequency such as 50 Hz power line frequency hum(not completed). 

38          Give an example of an intelligent instrument and write down its intelligent features.

39          What is 100 in a Pt-100 RTD?

100ohm resistance platinum RTD. Generally the resistance of RTD is 100ohm at 0   deg Celsius

40          What is the meaning of   ¾ in a 3¾-digit display digital instrument?

41          What is holding current in a thyristor?

It is the minimum current required to keep the thyristor in the ON state after being switched on.     It is the min current required to maintain the thyristor in conduction.      (latch is the min current to make the thyristor conducting) 

42          What is DPF in a power electronic circuit operation?

43          Power electronic loads are growing on the electrical power system. What are the        associated problems, which this growth creates on the power system?

         Use of power electronic loads produces harmonics , switching transients and lowers the power factor.

44          One of the popular four-bit BCD codes is 1-2-4-8 code. How many such four-bit BCD codes are possible?

         2-4-2-1 , Excess three , 8-4-2-1 , 84-2-1

45          What is the important facility offered by tri-state output devices?

         High impedance state along with logic one and logic zero.         It has 3 states: 2 logic(0&1) and 1 high impedance state. It remains in high impedance and doesn’t draw any current when not enabled

46          Do you prefer active pull-up or passive pull-up with respect to outputs of logic gates? Give reason.

47          What are characteristics of an ideal Op.Amp?

1.Infinite Voltage Gain      2.Infinite Input Impedance      3.0 output impedance      4.0 offset voltage      5.infinite CMRR      6.infinite Bandwidth   7.Infinite Slew Rate


 

48          Why “virtual ground” is called so in the context of Op.Amp. circuits?

 When the non-inverting terminal is grounded, the inverting terminal is also at ground potential though there s no physical connection between the inverting terminal and ground, by the concept of virtual short 

49          What is glitch phenomenon in a D/A converter?

50          How isolation between components is obtained in an IC?

There are 2 techniques i)p-n junction isolation: p+ type impurities are selectively diffused into n-type epitaxial layer so as to reach p-type substrate. This produces islands surrounded by p type moatsii)dielectric isolation: layer of solid dielectric such as silicon dioxide or ruby surrounds each component. 

51          What is anti-alias filter?

         The anti alias filter is used to prevent the overlap          It band limits the incoming analog signal to be sampled. (While sampling there will be some low frequency signals due to aliasing effect and lead to loss of information. To avoid aliasing we use analog lowpass filter before sampler to reshape the frequency spectrum of signal. This is called anti-aliasing filter.)

52          A digital filter is described by y (n)  =  {x (n) + x (n-1)}/ 2.  Is it an lpf, hpf or bpf?  y (n) and x (n) are respectively the output and input at the sampling instant n. 

53           A digital filter is described by y (n)  =   {y (n-1) + x (n)}/ 2. Is it an IIR or FIR filter?  y (n) and x (n) are respectively  the output and input at the sampling instant  n.

54          In what unique ways a DSP processor is different from a conventional μP?

(ask harsha) and tell him to post the message to the groups

55          What are the advantages of digital processing of signals in comparison with analog processing of signals?

         More flexible ; accurate ; easy storage ; cost effective          Greater accuracy, cheaper, flexibility in configuration, time sharing, ease of data storage.

56          What are the advantages of HVDC over HVAC?

         DC requires only two conductors , No skin effect, No synchronizing problem, Radio interference is neglected.Requirement  of  Reactive power is less in case of HVDC .Lesser Corona Loss and Radio InterferenceGreater ReliabilityThe contribution of dc line to short circuit is only upto rated current of dc line while ac line increases the short circuit current.  

57          What you understand by transposition of conductors in a transmission line?

         Transposition means exchanging the position of power conductors at regular intervals along the line so that each conductor occupies the original position of every other conductor over a equal distance.

58          Suggest methods to reduce corona loss in transmission lines?

         Large diameter , hollow conductor  and bundled conductor.Use of bundled conductors increases corona starting voltage and hence reduces loss.Increasing the conductor radius reduces surface field intensity and lesser loss.Hollow conductors.Because of field uniformity cylindrical conductor have less corona loss. 

59          What you understand by transmission efficiency in a transmission system?

It is the ratio of the power delivered at the receiving end to the power sent from the            sending end 

60          What is string efficiency?

         Η = ( S.O.V for the string ) / (n * S.O.V of one line) It is the measure of utilization of material in the string and is defined as the ratio of spark over voltage for the string to the product of number of insulators and spark over volt of one disc. 

61          What is a differential relay?

         Differential relay operates the vector difference between two or more similar  electrical quantities which exceed a predetermined value. It is one that operates when the vector difference of two or more similar electrical quantities exceeds a pre-determined value. This means the relay must have i) 2 or more similar electrical quantities and ii) such quantities should have phase displacement for operation. 

62          What is the application of a CT in protective schemes?

They are used in Split-phase relaying by which alternators are protected from short circuit of windings. In case of alternators with more than one coil per phase, the no. of ckts, when even, are divided into 2 = groups with CT for each group. When odd, CTs  with different ratings are used.(suggest something different) 

63          Suggest some important protection for a high capacity generator?

Rotor protectionOvervoltage protectionStator protectionRestricted earth fault protectionProtection of inter turn faults 

64          What is RRRV and how you control it?

         Rate of Rise of Recovery Voltage         The Rate of Rise of Restriking voltage is defined as the ratio of the peak value of restriking voltage to the time taken to approach the peak value. This can be prevented by resistance switching i.e, introducing a shunt resistor across the breaker

65          What are the basic criteria in selection of circuit breakers?

MVA rating, breaker value, fault currentNormal working power level specified as rated interrupting current or KVAThe fault level specified as either the rated short circuit interrupting current or MVAMomentary current ratingNormal working voltageSpeed of circuit breaker 

66          Mention the three important electrical engineering materials used in the manufacturing of electrical apparatus.

manufacturing of electrical apparatus.Various class of insulation materialsCopperAluminium(Refer Sawhney and confirm) 

67          Write the output equation for a DC machine and explain each term.

Pa = Co*(D^2)*L*nWhere Co= pi^2*Bav*ac*10^-3D-Diameter of the armatureL-length of the armaturen-speed in rpsCo-output coefficientBav-specific magnetic loadingac-Specific electric loading 

68          How the leakage fluxes in a transformer affect the performance of it?

69          Suggest design consideration to improve the power factor of an induction machine.

Pf can be improved by reducing the magnetizing current and leakage reactance.Reduce air gap length to decrease magnetizing current.The leakage reactance can be reduced by reducing depth of stator & rotor slots by providing short chorded winding and reducing the overhang in stator winding. 

70          What are the considerations you will have in selecting the speed of a synchronous generator?

The value of allowable peripheral speeds depends upon type of pole attachment. For bolted pole the peripheral speed is 50m/s. For dovetail and T-head the peripheral speed is 80m/s.Diameter also decides the peripheral speed. Limiting value for cylindrical rotor machine is 175m/s and 80m/s for salient pole machines.Peripheral speed Va=pi*D*nsHence selecting the speed of  synchronous generator depends on peripheral speed and dia of stator bore.(not sure refer sawhney) 

71          What you understand by management ethics?

Management of managerial ethics is essentially the study of morality and standards of  business conduct. The decisions made by manager within organization affect not only organization but its surrounding environment also. So they must be concerned with values and ethics. 

72          How does planning help in decision making?

Planning is the management function that involves setting goals, formulating missions and objectives then deciding how best to achieve them. Thus it gives a concrete base for decision making

73          What is the role of a manger in organizational development?

To develop an organization a manager should play a good interpersonal role, informational role and decisional role. Playing such roles makes a manager to act as leader, a liaison, a spokes person, an entrepreneur and a disturbance handler. 

74          What are the qualities of a good manager? Explain.

Drive – a high level of energyMotivation to lead– a strong desire to influence othersSelf confidence – strong belief in one’s own capabilitiesEmotional maturity – even-tempered and calm in face of stress and pressure.Leaders skills – good technical, conceptual and interpersonal skills 

75          Suggest some control techniques to improve productivity in your organization.

Financial or budgetary controlInventory controlMarketing controlOperations controlR & D controlHuman Resource control 

76          What are the main building blocks of a CPU?

         Control Unit ; Memory Unit ; Arithmetic Logic Unit

77          What assembly language instructions are used to input and output data in stack memory?

         Push ; Pop

78          What information is passed on from CPU to DMA controller for transfer of data between memory and peripheral?

79          What is the IEEE format for representing floating point numbers?

         Mantissa exponent separated e Single precision 32bits          Sign-1bit (1st field)         Exponent-8bits (2nd field)         Mantissa-23bits (3rd field)Double Precision 63bits         Sign-1bit         Exponent-1bit         Mantissa-52bits 

80          Why Load flow Analysis is performed?

To estimate line flows and line losses ; bus voltage ; real and reactive powers The study involves various methods of solution to power system network under steady state. The solution provides the voltages at various buses power flowing in various lines and line losses. It is essential to decide the best operation of existing system and for planning the future expansion of system. It is also important for designing a new power system. 

81          Establish relation between incidence matrix and primitive admittance matrix and Y-bus matrix.

Ybus= transpose[A]*[y]*[A]Where [A] is incidence matrix or singular matrix and therefore the given equation is a singular transformation of [y]. 

82          Why it is not preferred to obtain Z-bus by inverting Y-bus?

The matrix size becomes huge as the no. of buses in the system increases. So finding the inverse of such big matrix is a tedious job. Hence much simpler methods like bus building algorithm is used.(not sure) 

83          Distinguish between peripheral mapped I/O and memory mapped I/O.

MEMORY MAPPED I/O

PERPHERAL MAPPED I/O
1.            The device is treated as a memory address 2.            MEMR , MEMW are the control signals3.            Instructions used are STA, LDA, LDAX, STAX 1.            The device is treated as a peripheral device2.            IOR / IOW are the control signals.3.            IN and OUT are the instructions used

  Memory mapped I/O requires more hardware compared to Peripheral mapped I/O.Many instructions for memory related operations like sta,lda,stax,ldax ; only in and outMore T states(13-sta,lda;10-in,out)Memory  map s shared bet I/Os and sys memory, I/O map is independent of memory map and hence can connect more I/O devicesData transfer bet any reg and I/O in mem map, Only bet I/O and accumulator   

84          How the numbers of address lines in CPU are related with maximum addressable memory?

Total no. of memory locations  =  2n , where n is the number of  address lines.

 

11 Responses to “Q&A for Electrical Engineers”

  1. jakku said

    85 What you understand by transposition of conductors in a transmission line?
    Transposition means exchanging the position of power conductors at regular intervals along the line so that each conductor occupies the original position of every other conductor over a equal distance.
    86 Suggest methods to reduce corona loss in transmission lines?
    Large diameter , hollow conductor and bundled conductor.
    Use of bundled conductors increases corona starting voltage and hence reduces loss.
    Increasing the conductor radius reduces surface field intensity and lesser loss.
    Hollow conductors.
    Because of field uniformity cylindrical conductor have less corona loss.

    87 What you understand by transmission efficiency in a transmission system?
    It is the ratio of the power delivered at the receiving end to the power sent from the sending end

    88 What is string efficiency?
    Η = ( S.O.V for the string ) / (n * S.O.V of one line)

    It is the measure of utilization of material in the string and is defined as the ratio of spark over voltage for the string to the product of number of insulators and spark over volt of one disc.

    89 What is a differential relay?
    Differential relay operates the vector difference between two or more similar electrical quantities which exceed a predetermined value.

    It is one that operates when the vector difference of two or more similar electrical quantities exceeds a pre-determined value. This means the relay must have i) 2 or more similar electrical quantities and ii) such quantities should have phase displacement for operation.

    90 What is the application of a CT in protective schemes?
    They are used in Split-phase relaying by which alternators are protected from short circuit of windings. In case of alternators with more than one coil per phase, the no. of ckts, when even, are divided into 2 = groups with CT for each group. When odd, CTs with different ratings are used.(suggest something different)

    91 Suggest some important protection for a high capacity generator?
    Rotor protection
    Overvoltage protection
    Stator protection
    Restricted earth fault protection
    Protection of inter turn faults

    92 What is RRRV and how you control it?
    Rate of Rise of Recovery Voltage
    The Rate of Rise of Restriking voltage is defined as the ratio of the peak value of restriking voltage to the time taken to approach the peak value. This can be prevented by resistance switching i.e, introducing a shunt resistor across the breaker
    93 What are the basic criteria in selection of circuit breakers?
    MVA rating, breaker value, fault current
    Normal working power level specified as rated interrupting current or KVA
    The fault level specified as either the rated short circuit interrupting current or MVA
    Momentary current rating
    Normal working voltage
    Speed of circuit breaker

    94 Mention the three important electrical engineering materials used in the manufacturing of electrical apparatus.
    manufacturing of electrical apparatus.
    Various class of insulation materials
    Copper
    Aluminium(Refer Sawhney and confirm)

    95 Write the output equation for a DC machine and explain each term.
    Pa = Co*(D^2)*L*n
    Where Co= pi^2*Bav*ac*10^-3
    D-Diameter of the armature
    L-length of the armature
    n-speed in rps
    Co-output coefficient
    Bav-specific magnetic loading
    ac-Specific electric loading

    96 How the leakage fluxes in a transformer affect the performance of it?
    97 Suggest design consideration to improve the power factor of an induction machine.
    Pf can be improved by reducing the magnetizing current and leakage reactance.
    Reduce air gap length to decrease magnetizing current.
    The leakage reactance can be reduced by reducing depth of stator & rotor slots by providing short chorded winding and reducing the overhang in stator winding.

    98 What are the considerations you will have in selecting the speed of a synchronous generator?
    The value of allowable peripheral speeds depends upon type of pole attachment. For bolted pole the peripheral speed is 50m/s. For dovetail and T-head the peripheral speed is 80m/s.
    Diameter also decides the peripheral speed. Limiting value for cylindrical rotor machine is 175m/s and 80m/s for salient pole machines.
    Peripheral speed Va=pi*D*ns
    Hence selecting the speed of synchronous generator depends on peripheral speed and dia of stator bore.(not sure refer sawhney)

    99 What you understand by management ethics?
    Management of managerial ethics is essentially the study of morality and standards of business conduct. The decisions made by manager within organization affect not only organization but its surrounding environment also. So they must be concerned with values and ethics.

    100 How does planning help in decision making?
    Planning is the management function that involves setting goals, formulating missions and objectives then deciding how best to achieve them. Thus it gives a concrete base for decision making
    101 What is the role of a manger in organizational development?
    To develop an organization a manager should play a good interpersonal role, informational role and decisional role. Playing such roles makes a manager to act as leader, a liaison, a spokes person, an entrepreneur and a disturbance handler.

    102 What are the qualities of a good manager? Explain.
    Drive – a high level of energy
    Motivation to lead– a strong desire to influence others
    Self confidence – strong belief in one’s own capabilities
    Emotional maturity – even-tempered and calm in face of stress and pressure.
    Leaders skills – good technical, conceptual and interpersonal skills

    103 Suggest some control techniques to improve productivity in your organization.
    Financial or budgetary control
    Inventory control
    Marketing control
    Operations control
    R & D control
    Human Resource control

    104 What are the main building blocks of a CPU?
    Control Unit ; Memory Unit ; Arithmetic Logic Unit
    105 What assembly language instructions are used to input and output data in stack memory?
    Push ; Pop
    106 What information is passed on from CPU to DMA controller for transfer of data between memory and peripheral?
    107 What is the IEEE format for representing floating point numbers?
    Mantissa exponent separated e

    Single precision 32bits
    Sign-1bit (1st field)
    Exponent-8bits (2nd field)
    Mantissa-23bits (3rd field)
    Double Precision 63bits
    Sign-1bit
    Exponent-1bit
    Mantissa-52bits

    108 Why Load flow Analysis is performed?
    To estimate line flows and line losses ; bus voltage ; real and reactive powers

    The study involves various methods of solution to power system network under steady state. The solution provides the voltages at various buses power flowing in various lines and line losses. It is essential to decide the best operation of existing system and for planning the future expansion of system. It is also important for designing a new power system.

    109 Establish relation between incidence matrix and primitive admittance matrix and Y-bus matrix.
    Ybus= transpose[A]*[y]*[A]
    Where [A] is incidence matrix or singular matrix and therefore the given equation is a singular transformation of [y].

    110 Why it is not preferred to obtain Z-bus by inverting Y-bus?
    The matrix size becomes huge as the no. of buses in the system increases. So finding the inverse of such big matrix is a tedious job. Hence much simpler methods like bus building algorithm is used.(not sure)

    111 Distinguish between peripheral mapped I/O and memory mapped I/O.
    MEMORY MAPPED I/O PERPHERAL MAPPED I/O
    1. The device is treated as a memory address 2. MEMR , MEMW are the control signals3. Instructions used are STA, LDA, LDAX, STAX 1. The device is treated as a peripheral device2. IOR / IOW are the control signals.3. IN and OUT are the instructions used

    Memory mapped I/O requires more hardware compared to Peripheral mapped I/O.
    Many instructions for memory related operations like sta,lda,stax,ldax ; only in and out
    More T states(13-sta,lda;10-in,out)
    Memory map s shared bet I/Os and sys memory, I/O map is independent of memory map and hence can connect more I/O devices
    Data transfer bet any reg and I/O in mem map, Only bet I/O and accumulator

    112 How the numbers of address lines in CPU are related with maximum addressable memory?
    Total no. of memory locations = 2n , where n is the number of address lines.

    113 What is 8255? Where it is used?
    Programmable peripheral interface . It can be programmed to transfer data under various conditions.

    It is Programmable Peripheral Interface, widely used Parallel I/O device. It s used with almost any microprocessor in applications such as automated temperature control and to turn on/off a switch through its BSR mode.

    —————- ———————— –
    114 What is a transfer instrument? Give an example.
    A transfer instrument is one which is calibrated in DC and can be used in AC without any modification. Ex: Electrodynamometer type instrument.
    115 What are the merits, if any, of IGBTs compared with SCRs?
    IGBT has less switching losses , comparatively faster switching time.
    116 Compare CMOS with TTL family with respect to speed, power consumption and noise immunity.
    CMOS is faster ; Power dissipation is extremely low (10nW); excellent noise immunity.
    117 Do you prefer linear phase characteristic in a filter? Give reason.
    ————————————-
    118 Give one practical application of a four-terminal resistor. Why such an application
    needs a four-terminal resistor?
    119 Can you use an autotransformer as a variable inductor? Give reason.
    Yes, the tap can be changed to use it as a variable transformer
    120 What is the meaning of each of the following symbols and that of ‘Class 1.5’
    printed on the face plate of an indicating instrument?
    121 What is the A/D conversion technique that can be made immune to power supply hum riding on the signal? How would you realize this immunity?
    122 What is a CPLD and what are its any three applications? What is VHDL?
    123 Show the directions of torque and speed in the four quadrants of a four-quadrant drive of a motor.
    124 What is the type of motor used in the following domestic appliances: i. Washing
    machine ii. Hair dryer iii. Grinder and iv. Vacuum cleaner?
    Washing machine :-
    Hair dryer :-fractional horse power permanent magnet motor
    Grinder :-AC series motor
    Vaccum cleaner :-
    125 What are the voltage levels employed in RS232 and in RS485? What is the
    maximum distance recommended for data communication under each standard?

    126 What are the advantages and disadvantages of the following control modes of a PID
    controller: i. derivate control mode and ii. Integral control mode?
    Derivative control mode responses to rate of change of error
    Integral control mode responses to minimize the steady state error
    127 It is required to produce TTL compatible 60 pulses per rotation of a shaft in
    measuring the speed of the shaft. Explain with necessary diagrams a technique to
    realize this objective.
    128 Why a neutral link rather than a fuse wire must be used in the neutral line of the domestic power supply connection?
    Because when the fuse connected to the neutral is blown the operator may still get a shock
    129 In the circuit shown below, what is the output voltage Vo when R is i. 47kΩ and ii.
    10kΩ? Assume ideal Op.Amp.
    130 Which type of indicating ammeter (moving iron, PMMC, dynamometer, rectifier) would you prefer to measure the dc current flowing through the magnetizing coil, in the experiment to determine the hysteresis loop of a magnetic material? Give reason.
    PMMC — for pmmc torque is proportional to avg value of voltage
    131 To observe the waveform of the current i (t) flowing in the circuit shown below, an experimenter inserts the resistor R of 0.2Ω between points ‘a’ and ‘b’ in the circuit and intends to connect the point ‘a’ to the Y1-channel of a CRO and the point ‘b’o the GND of the CRO. Is the experimenter right in doing so? Give reason.If the experimenter is not right, suggest the correct procedure to observe the waveform of the current on the CRO.
    132 It is required to realize a system whose input-output relation is given by

    y (t) = u (t-5)

    where y (t) is the output for time t≥0 and u (t) is the input for time t≥0. Note that the system is a pure delay system. How will you realize this system in practice?
    133 What are difficulties in measuring very high resistance (e.g. insulation resistance) and very low resistance (e.g. shunt resistance of a PMMC ammeter)?
    134 What is the meaning of ‘plug and play’ of a plug and play data acquisition board?
    135 Which motor can be used for driving magnetically elevated vehicles?
    136 A synchronous machine is connected to the grid. How will you increase it’s a) Active lower Output b) Reactive Power Output?
    137 What will happen if a wooden core is used for a transformer?
    138 What are the advantages of an ungrounded system?
    Critical system like Artificial breather does not go out even if there is a short circuit
    139 Why a guard wire is used while measuring the insulation resistance of a machine or a cable?
    140 What is the relation between Power and Wind velocity as applied to a wind turbine?
    141 A d.c. series motor can work on a.c. whereas a d.c. shunt motor doesnot work on a.c. why?
    142 What are the differences between d.c. and a.c. amplifiers? Give one example of each.
    ————————- —————— ————————— ———-
    143 What are the two basic electrical measurements you are supposed to take before energizing a new three-phase induction motor? Armature resistance and winding IR value.
    144 What are the different operating voltages for meggers? 500v, 1kv, 2.5kv and 5kv
    145 Where do you prefer the usage of an electrically operated megger instead of a hand operated one? Mainly to measure PI value (R10/ R1) of insulation resistance of high voltage high capacity motors and generators.
    146 What is the type of sensor you would recommend for measuring a temperature in the range of ambient to 1000oC? Does your sensor require any compensation? Explain. Thermocouple. Yes. Cold junction compensation for the voltage developed at thermocouple field terminal point which is affected by varying ambient conditions which in turn affect the mv output of the thermocouple
    147 What is a growler? This is a transformer with an open core, which is used to detect faulty windings (interterm short/open) of a rotor with commutator.
    148 What is the significance of “tan δ” measurement in the case of ac machines? This is a measure of healthy winding insulation which done form high capacity motors and generators. The increase in value of “ tan δ ” indicates deterioration of winding insulation.
    149 What are the necessary conditions to be satisfied for paralleling of a synchronous generator with the grid? Equal voltage, equal frequency, same phase and same phase sequence.
    150 Draw a circuit for testing a thyristor and explain the procedure. DC source in series with a loading rheostat and a voltage divider circuit for gate triggering. Necessary voltmeter and ammeter in the circuit. Vary the trigger voltage with the voltage divider and check whether the thyristor is conducting or not.
    151 What is the difference between an isolator and a circuit breaker? Explain their application in a power system. Isolator is a no load device which is used to isolate certain portion of a network from other systems. It is always manually operated device at the discretion of the operator for no load isolation and maintenance works. Circuit breakers are operable either manually for on load isolation or automatically on fault in the system, thus isolating the faulty system from a healthy system
    152 Why vegetable oil is not used for cooling of transformer? Vegetable oils contain fatty acids, which attack the type of insulation used in the transformer affecting the life and performance of the insulation of the transformer.
    153 What is the normal dielectric value of good transformer oil? As per corning standard the value is 25kv for 1minute at a sphere gap of 2.5mm.it is also sometime taken as 40kv for 1minute for a sphere gap of 4mm
    154 Suggest a method to improve the dielectric value of transformer oil. This is normally done by what is called oil filtration by using a filter machine. In high capacity transformers the oil is heated, centrifuged and circulated through the windings keeping them under a small value of vacuum
    155 Why neutral in a power system is to be grounded? This is very much required to maintain the phase voltages equal under varying loadings of the different phase. Some other considerations are like preventing arcing grounds in generators, for functioning of protective systems in the power systems
    156 What is the requirement of earthing of electrical equipments? This is mainly done for safety of the operating personnel. Earthing also protects transmission lines and electrical equipments by diverting large currents during lightning.
    157 Why 60Hz is chosen as the supply frequency in USA? For producing 60Hz the machine has to run at a high speed, which means the machine size can be reduced for a given capacity. Thus weight is reduced and hence cost of material is reduced. In case of a transformer for a higher frequency the flux can be reduced for the same voltage thus size is reduced.
    158 Draw the circuit for a three-phase thyristor controlled full wave rectifier bridge. Six thyristors connected in parallel combination of three sets of thyristors connected in series in the same direction. Three-phase supply wires are connected to the junction of two thyristors connected in series and the rectified DC voltage is taken from the two common points of all the six thyristors.
    159 Which electrical shock will be severe in nature, AC/DC and why? DC. Even though the peak voltage is more in ac since the current is of oscillatory nature it varies between zero /max and there is always the possibility of saving ones life at the instant when current goes to zeros 100 times per second.
    160 What is the installed capacity of wind power generation in India and in Tamilnadu? 2000MW, 1000MW
    161 What is the type of generator used for mini power plants like wind power generators and small hydropower generators? Give one reason for its usage. Induction generators. Simplicity of construction and maintainence.by providing capacitor banks the machine can be run and self excited generator
    162 Differentiate between sparking and arcing. Sparking is an intermittent flow of current due to ionization of air medium. Arcing is a continuous flow of current.
    163 It is required to measure accurately the rms value of the voltage across an RL load fed by a half-controlled rectifier operating from single-phase supply. Which type of meter would you prefer for this measurement? Give reason. Dynamometer type ammeter may be used. Moving iron meter may also be used but it will be less accurate. Multimeters using rectifier type PMMC should not be used as these measure rectified average value as calibrated for RMS value for a pure sine wave. Here the waveshape is not sinusoidal.
    164 Why the secondary of a current transformer in active operation should not be open circuited? The secondary to primary turns ratio of a ct is very large and under open circuit condition a very large voltage will be induced which is injurious to the insulation and the person handling the CT. Flux in the core will also reach to very high value, changing the characteristics of the core material permanently.
    165 What is an ELCB? What is its application? Earth leakage circuit breaker. This primarily used in household premises to protect the personnel handling the power equipments. When the current through the person is more than a specific value say 40ma or so the circuit breaker trips isolating the power supply and saving the life of the person. It trips instantaneously.
    166 Define stability. Why a rod standing in perfectly vertical position is unstable according to this definition? If one of the parameter of a system is varied by an infitisimal small value and the system develop such transients as to restore the initial working conditions, the system is said to be stable. Perfectly vertical rod is unstable as a very small tilt in any direction will develop torque to tilt it further.
    167 Why a sensitive permanent magnet galvanometer is kept shorted while not in use? In these galvanometers, only electromagnetic damping is provided, hence if open circuited, on occurrence of a small mechanical jerk, the coil will keep on oscillating for a very long time. If shorted, current will be flowing in the coil producing a torque in a direction to prevent the movement of the coil as per Lenz’s law.
    168 What is the single purpose of transmitting power at high voltages?
    Losses are minimum because high voltage and low current.
    à higher efficiency,I^2 R loss less as currents less ….

    169 A power system is operated as an interconnected system rather than isolated blocks. Why?
    -uninterrupted power supply
    -load sharing
    àstability,efficiency of operation,security
    170 The instantaneous values of voltage (v) and current (i) across and through a circuit element are given by :
    v(t) = √2V Cos(ωt – ά) Volt and

    i(t) = √2I Sin(ωt – β) Ampere.
    What is the average power consumed by the circuit element? Give your answer in terms of V,I,ά,β and ω.
    171 The active power or real power associated with an electrical ac circuit under
    steady state is the average value of the instantaneous power associated with
    that circuit under steady state. What can you say about the reactive power
    associated with the circuit?
    The average value of the reactive power is ZERO
    172 Industrial consumers who operate their loads at low power factor have to
    pay additional charge. Why is the additional charge?
    Reactive power is sent into the power system because of low power factor equipments (inductive reactance i.e XL is increased).
    Increases the rating of station equipments and line losses.

    à I = (P/V cosf), when V is constant , I increases with low pf, so line losses & drop increase, so penalty

    173 What is a relay? How is this different from a circuit breaker?
    Relay is a device that detects the fault and initiates the operation of the circuit breaker to isolate the defective elements from the rest of the system.
    174 What are the typical protections employed in transformers used in power system?
    Buchholz relay : to detect incipient fault inside the oil tank
    Differential protection relay : to detect unbalance current.
    Pressure release valve : to detect the internal oil pressure.

    175 What will be the consequences if the alternators of a power system are operated with (a) constant excitation and (b) constant prime mover power?
    (a) constant excitation – constant terminal voltage with load remaining constant
    (b) constant prime mover power – constant frequency with load remaining constant.
    176 What is the single pointer to indicate the healthy state of a power system?
    Frequency
    177 In power system operation, control requirement on frequency is rigid while that on voltage is not so rigid. Why?
    Most types of A. C motors’ speed directly depend on frequency. The generator turbine particularly steam driven ones are designed to operate at a very precise speed. The overall operation of the power system can be controlled much easily if the freq is within fixed limit. Large number of electrically operated clocks and synch. motors is a function of frequency
    178 Why alternators used in power generation are Y-connected?
    Y connetion has a neutral which is connected to the ground and the imbalance current is grounded.3 phase supply can be used as 3 single phases
    179 What are the unique advantages of 3-phase power compared with 1-phase power?
    For same voltage in single phase more power can be delivered in 3 phase
    1 phase power = VIcosφ , 3 phase power =1.732VIcosφ
    Power factor will be improved.
    Material used for same power delivered in single phase will be more compare to power delivered in three phase
    180 What is in-rush current in a transformer? How does it happen? Can you prevent it?
    When the transformer is switched on back emf is absent. So the current is very high. This is called inrush current. This can be prevented by using shunt inductors.
    181 Three-phase power is transformed by use of three-phase transformers. However, in large EHV systems, a bank of three single-phase transformers is connected in three-phase arrangement. Why?
    The size of the transformer will be very big as a result total floor space required will be high and moreover there will be insulation problem.
    182 What is a three-winding transformer used in power system operation?
    The third winding called tertiary winding is used for injection of reactive power in the system and for connecting HV measuring devices.
    183 (a). Consider a 1000V,50Hz single-ended source which can provide a
    maximum current of 1.0mA. Will you experience electrical shock when
    you come into contact with the live terminal of the source?
    (b) Repeat part (a), if the source is 5.0V,50Hz capable of providing a
    maximum of 10.0A.
    (c). Repeat part (a), if the source is your house-hold single-phase supply.
    Yes for all the 3 parts.
    184 A 230V,50Hz mains is connected across an impedance load through a thyristor.The impedance load is initially relaxed. The thyristor is triggered only once at the instant when the supply voltage waveform has maximum positive value. In response to this triggering, sketch the waveform of the current through and voltage across the load Z when (a) Z is a pure resistance(R) ,(b) Z is R and L in series and (c) Z is R and C is series.Show two cycles of waveforms of supply voltage and the corresponding wave forms of load voltage and load current. Assume that the thyristor
    is triggered in the first cycle of the supply voltage waveform.
    185 Explain how the “virtual” ground terminal of an Op.Amp. in a circuit
    justifies to be called so.
    186 It is a recommended practice to connect the tube-lights in the different
    phases of the three-phase supply in a machine-tool shop. Why not in any
    one single-phase?
    187 Mention any specific five applications of power electronics.
    SMPS , Rectifiers , Inverters , Chopper , Cycloconverters.
    188 What is a DC transformer?
    Chopper is known as dc transformer.
    189 What do you mean by linear phase characteristic of an amplifier? Is it desirable for an amplifier?
    190 What are the three pointers to assess the quality of a power system from the consumers’ point of view?
    Voltage , frequency and power factor
    191 It is required to provide 50V dc across a resistive load of 5.0 Ohms. Given a dc source of 100V dc of compatible current rating, suggest different methods to achieve the objective. Which of the methods you would prefer?
    By connecting a 5 ohm resistance in series with it , also by using a chopper with a duty cycle of 0.5
    192 Consider the circuits Figure (a) and Figure(b) shown below. The circuits are in the steady state with the switches in the closed position. The switches are opened at t = 0. What is the voltage across the switch contacts at t = 0+ in each circuit? Comment on your answers.
    193. Why polarity of connection is not important while measuring dc currents and voltages using a MI instrument?
    The deflecting torque is directly proportional to the square of the RMS value the operational current. So the deflecting torque is unidirectional whatever may be the direction of operational current
    194. A 20A dc current is suddenly passed through a PMMC ammeter with a wrong polarity of connection. What will be the consequence if the range of the meter is (i) 5A and (ii) 25A?
    195. It is required to measure the rms value of the square wave output voltage of an astable multivibrator . Can you use a rectifier type voltmeter? Give reason. No. Rectifier type of instruments are calibrarated in terms of RMS values of sin current and voltage.
    196. What is the most important restriction is using rectifier type instruments in measuring currents and voltages?
    It can be used only to measure sinusoidal current and voltage.
    Effect of rectifier resistance and capacitance
    197. Can you use a MI voltmeter to measure the rms value of a sinusoidal voltage having a frequency of 5000Hz? Give reason.
    No. MI instruments are suitable for measuring upto 125 hz. Change in frequency may cause error due to changes in reactance of the working coil.
    198. Can you use a rectifier type ammeter to measure the rms value of a sinusoidal current having a frequency of 1Hz? Give reason.
    199. It is required to measure accurately the rms value of a voltage having non-sinusoidal periodic waveform. Which type of meter is to be recommended?
    Electrodynamometer
    200. What is a True RMS meter? Why a rectifier type meter is not a TRMS meter?
    RMS meter are used to measure the complex waveforms most accurately. Rectifier type meter is not a true RMS meter because it is calibrated only for pure sin wave.
    201. What is a transfer instrument? Why it is needed?
    A transfer instrument is one that can be calibrated with a D.C source and then used to measure A.C without any modification
    202. What are the advantages of a DMM compared with an analog multimeter? What is the purpose of providing a bar graph on DMMs?
    Advantages of DMM
    – High accuracy
    – High input impedance
    – Smaller in size
    203. Why one has to pay due attention in choosing a dynamometer type wattmeter for measuring power in a low-power factor circuit?
    The wattmeter will read high value at lagging pf loads and low in leading pf loads.This is due to pressure coil inductance.
    204. What is the A/D conversion technique which can be made immune to power supply hum? How it can be accomplished?
    Dual slope

    àdual slope type…….by making the constant time an integral multiple of power supply period

    205. What is the A/D conversion technique, which is fastest?
    Flash type A/D
    206. Mention an A/D conversion technique, which has a constant conversion time. Is there any advantage with constant conversion time? Explain.
    207. What is the A/D conversion technique more often used in DMMs?
    Dual slope method is used.
    208. 20-V dc voltage is measured by an analog multimeter and a DMM. The analog instrument is on its 25V range and its specified accuracy is 2%.The DMM has a 3 ½digit display and an accuracy of (0.5% + 1digit). What is the measurement accuracy in each case?
    209. Why ammeters should have as low resistance as possible and voltmeters as high resistance as possible. Explain this statement by means of examples using necessary circuit diagrams.
    Ammeters are connected in series in the circuit. The power lossin the circuit is I square R. Therefore ammeter should have low resistance. Voltmeter are connected in parallel with circuit. Power loss in the circuit is Vsquare/R. So voltmeter should have high resistance
    210. A TTL square wave periodic signal is connected to a CRO. Sketch the waveform of the signal displayed by the CRO when the AC-DC-GND switch is in the (i) DC position, (ii) AC position and (iii) GND position.
    211. What is the purpose served by the AC-DC-GND switch of an oscilloscope? What is the meaning of DC in this context?
    212. Three impedances Z1,Z2 and Z3 are connected in series in that sequence across the phase(P) and neutral(N) of a 230V,50Hz supply mains. It is required to observe and analyze the waveform of the voltage across Z2 using a CRO.Explain any one satisfactory method of connections to the CRO with necessary circuit diagram For your method , if the CRO is to have certain special provision, state that provision.
    213. A diode, a resistor and an inductance are connected in series in that sequence across the phase(P) and neutral(N) of a 230V,50Hz supply mains. It is required to observe the waveforms of the voltage across the diode and the current through the circuit using a conventional two-channel CRO. Explain how you will conduct this experiment ; draw necessary circuit diagram of connections.
    214. Under certain measurement –situation, one may like to operate an oscilloscope through an isolation transformer or by using a two-pin plug to power the scope.Is there any problem with this procedure? Explain with a circuit diagram.
    215. Explain how the earth wire of a three-wire power cord acts as a protective mechanism against electric shock hazards.
    216. Explain what may happen if a washing machine is operated from the ac mains, however, without being earthed.
    217. Protective fuses for equipment are connected only on the phase-line; no fuses are connected on the neutral-line. Why?
    218. Service connections to consumers are normally 3-phase,4-wire rather than 3-phase,3-wire.Why?
    219. What are the four terminals of a four-terminal resistor? What purpose is served by a four-terminal resistor? Give one application of such a resistor.
    220. What is the purpose served by a guard wire while measuring a large resistance, say, the insulation resistance of a cable? Draw necessary diagrams to illustrate your answer.
    221. Can a 2 ½ digit digital voltmeter measure 1mV if its basic range is 0 to 100V?
    222. What is an intelligent or smart instrument? Give any two intelligent features of such an instrument.
    223. Which is the fastest A/D conversion technique? Which is the slowest one?
    Fast : Flash type
    Slow : Dual slope
    224. What are the four important motivations for providing feedback in a control system?
    225. What is the most important characteristic that you should provide in a control system?
    226. Why the derivate control action is not recommended in an electrical noisy environment?
    227. What are the basic building blocks you will need to build up a control system for controlling the speed of an induction motor? What is the function performed by each of the building blocks you need?
    228. Power electronic loads are growing on the electrical power system. What are the associated problems which this growth creates on the power system?
    229. A 3-phase resistive star- connected load is fed from a 3-phase supply and the load consists of 23 Ohm in the R-phase,92 Ohm in the Y-phase and 184 Ohm in the B-phase. Determine the voltage across each phase-load when (i) the neutral of the 400 V,50Hz,3-phase supply is connected to the star-point of the load and (ii) the neutral of the 3-phase supply is not connected to the star-point of the load. Comment on your answers.
    230. It is required to determine the v-i characteristics of a signal diode in its reverse biased condition. Draw the circuit diagram of connections to perform this experiment using PMMC instruments and other accessories.
    231. What are the main problems encountered while measuring (i) very high resistance and (ii) very low resistance? How such problems are handled in practice?
    232. It is required to observe the waveform of the starting current in one phase of a 3-phase induction motor started using a direct on-line starter. Explain how youwill realize this experimental objective using an oscilloscope. Draw necessary diagrams to illustrate your explanation; indicate any other accessories you needand also any special features you need in the oscilloscope or any special oscilloscope.Are there any disadvantages associated with a DMM in comparison with an analog multimeter?

    233 What is a 3 ½ digit display DMM? What is a 3 ¾ digit display DMM?
    What is a 4 ¾ digit display DMM with a 50000 count?

    à3 ½ means it has four display digits with msb able to display only 0/1
    3 ¾ means the msb can display only 0,1,2,3
    4 ¾ with 50000 count is one that can display maximum of 50000 only…

  2. […] Q&A for Electrical Engineers […]

  3. […] Q&A for Electrical Engineers […]

  4. Allen said

    I need to find out the difference between the three phase connection: the advantages and the disadvantages of all three

  5. Ro said

    On my current design I need to add ground fault circuit to it. I have multiple power source (+/- 5VDC, +10VDC, +12VDC and 24VDC and 24VDC) on the circuit. They all are sharing common ground. Is there anyway I can design grand fault circuit without isolating each ground. Please avice. Thanks

  6. Daniel chukwudi said

    Explain why a double ratio transformer bridge may be used to measure the characteristics of any two or three terminal network.

  7. Daniel chukwudi said

    Determine the series component of an unknown impedence if the displayed values for bridge balance were 5.32mS and -2.67 nF at a frequence of 5kHz.

  8. Solid website=) will come back again soon=)

  9. abinash said

    It is just awesome…… Nice to have those q/a selection….. Simply Gr8……….

  10. please explain the formulation of ybus by the singular transformation method in the power system analysis

  11. want to know some………

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

 
%d bloggers like this: