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    3 Hours / 100 Marks: Seat No

    Uploaded by

    sahil satpute
    The document provides instructions for a 3 hour, 100 mark exam on electrical machines. It outlines 7 instructions for the exam, including that all questions are compulsory and to assume suitable data if necessary. It then lists the 6 main exam questions covering topics like DC machines, transformers, transformer testing, and transformer applications. Each question is worth between 16-20 marks and students are instructed to answer 10 out of 20 parts in question 1 and 4 out of 6 questions for the remaining questions.

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    3 Hours / 100 Marks: Seat No

    Uploaded by

    sahil satpute
    21 views4 pages
    The document provides instructions for a 3 hour, 100 mark exam on electrical machines. It outlines 7 instructions for the exam, including that all questions are compulsory and to assume suitable data if necessary. It then lists the 6 main exam questions covering topics like DC machines, transformers, transformer testing, and transformer applications. Each question is worth between 16-20 marks and students are instructed to answer 10 out of 20 parts in question 1 and 4 out of 6 questions for the remaining questions.

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    The document provides instructions for a 3 hour, 100 mark exam on electrical machines. It outlines 7 instructions for the exam, including that all questions are compulsory and to assume suitable data if necessary. It then lists the 6 main exam questions covering topics like DC machines, transformers, transformer testing, and transformer applications. Each question is worth between 16-20 marks and students are instructed to answer 10 out of 20 parts in question 1 and 4 out of 6 questions for the remaining questions.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    21 views4 pages

    3 Hours / 100 Marks: Seat No

    Uploaded by

    sahil satpute
    The document provides instructions for a 3 hour, 100 mark exam on electrical machines. It outlines 7 instructions for the exam, including that all questions are compulsory and to assume suitable data if necessary. It then lists the 6 main exam questions covering topics like DC machines, transformers, transformer testing, and transformer applications. Each question is worth between 16-20 marks and students are instructed to answer 10 out of 20 parts in question 1 and 4 out of 6 questions for the remaining questions.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 4

    17415

    16117
    3 Hours / 100 Marks Seat No.

      Instructions – (1) All Questions are Compulsory.


    (2) Answer each next main Question on a new page.
    (3) Illustrate your answers with neat sketches wherever
    necessary.
    (4) Figures to the right indicate full marks.
    (5) Assume suitable data, if necessary.
    (6) Use of Non-programmable Electronic Pocket
    Calculator is permissible.
    (7) Mobile Phone, Pager and any other Electronic
    Communication devices are not permissible in
    Examination Hall.

    Marks

    1. Attempt any TEN of the following: 20


    a) State Fleming’s right hand rule.
    b) State working principle of DC generator.
    c) State atleast four applications of DC series motor.
    d) DC series motor should never be started at no load. Justify.
    e) Write emf equation of DC short shunt compound motor in the
    form of their voltage drop.
    f) State any two applications of Brushless DC motors.
    g) State any four properties of ideal transformer.
    h) Define all day efficiency.
    i) State why a transformer always have a efficiency of more than
    90%.
    j) A 3  kVA, 220/110V transformer has 500 turns on its primary.
    Find its transformation ratio and secondary turns.

    P.T.O.
    17415 [2]
    Marks
    k) Give the specification of three phase transformer as per IS 1180
    (Part-1) 1989 (any four)
    l) Give the criteria for selection of distribution transformer as per
    IS : 10028 (Part - I) 1985.

    2. Attempt any FOUR of the following: 16


    a) Drive the EMF equation of DC generator.
    b) A DC generator has an armature emf of 100 V when the usefull
    flux per pole is 20  mmWb and the speed is 800  r pm. Calculate
    the generated emf:
    (i) With the same flux and speed of 1000  R PM,
    (ii) With a flux per pole of 24  mmWb and a speed of 900  R PM.
    c) Explain the necessity of starter for DC motor. State various types
    of DC motor starter.
    d) Describe Ta-Ia characteristics for DC series and DC shunt motor.
    e) A 250  V shunt motor on no load runs at 1000 RPM and takes
    5A. The total armature and shunt field resistance are respectively
    0.2W and 250W. Calculate the speed when loaded and taking a
    current of 50A, if armature reaction weakens the field by 3%.
    f) A 230V DC shunt motor takes 4 A at no load. The armature
    and field resistance are 0.8W and 250W respectively. Calculate
    full load efficiency when the current is 22A.

    3. Attempt any FOUR of the following: 16


    a) Draw the equivalent circuit of transformer refferred to primary.
    State the meaning of each term related to equivalent circuit.
    b) List the advantages of OC and SC test (any four)
    c) A 3300/250V, 50 Hz single phase transformer is built on a cone
    having an effective cross sectional area of 125 cm2 and 70 turns
    on the low voltage windings Calculate:
    (i) the value of the maximum flux density
    (ii) number of turns on the high voltage windings.
    d) Explain concept of an ideal transformer with its properties.
    e) List the conditions for parallel operation of three, phase transformer.
    f) Explain with neat diagram construction and working of a current
    transformer.
    17415 [3]
    Marks
    4. Attempt any FOUR of the following: 16
    a) Derive the condition for maximum efficiency of transformer.
    b) A 500 kVA transformer has 2500  W iron loss and 7500  W copper
    loss at full load. Calculate its efficiency at full load at unity p.f.
    and 0.8  p.f lagging.
    c) Two single phase transformer of 250  kVA each are operated on
    parallel (both side) their % drops are (1 +  j6)W and (1.2  +  j4.8)W.
    The load connected across the bus bar is 500  kVA at 0.8  p.f. log.
    Calculate load shared by each transformer.
    d) Draw experimental setup to conduct OC and SC test on a 2.5  kVA,
    220 V  / 115V, 50  Hz, single phase transformer. Select the ranges
    of meter used for test.
    e) List the various losses in a transformer, the places at which they
    occur. And list the methods to minimize these losses.
    f) Explain construction and operation of 3 phase auto transformer.

    5. Attempt any FOUR of the following: 16


    a) Draw the complete phasor diagram of transformer for lagging p.f
    load condition and leading pf load condition.
    b) State the advantages of amorphous core type distribution transformer.
    c) A 500  kVA, distribution transformer having copper and iron
    losses of 5  kW and 3 kW and 3 kW respectively on full load. The
    transformer is loaded as shown below.
    Loading (kW) Power factor (log) No. of hours
    400 0.8 06
    300 0.75 12
    100 0.8 03
    No load - 03
    Calculate all day efficiency.
    d) Draw a neat diagram of scott connected three phase transformers
    and explain the working.
    e) Compare between distribution transformer and power transformer
    (any four points)
    f) Explain the criteria of selection of power transformer.

    P.T.O.
    17415 [4]
    Marks
    6. Attempt any FOUR of the following: 16
    a) A single phase 3300/400  V transformer has the following winding
    resistances and reactances R1  =  0.7W, R 2  =  0.011W, X1  =  3.6 W,
    X 2  =  0.045W. The secondary is connected to a coil having
    a resistance of 4.5W and inductive reactance 3.2W. Calculate
    secondary terminal voltage and the power consumed by the coil.
    b) Explain the different types of transformer cooling.
    c) Compare two winding transformer with auto transformer on the
    basis of construction, copper loss, output voltage variation and
    cost.
    d) Explain with circuit diagram use of potential transformer to
    measure 33  kV.
    e) Explain construction and working of isolation transformer.
    f) List special features of welding transformer.

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