B.TechSemester 42021-22Electrical Machines IKEE402
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Electrical Machines I (KEE402) - AKTU Question Paper 2021-22

B.Tech · Semester 4 · Free PDF Download

This is the official AKTU Electrical Machines I Previous Year Question Paper for B.Tech Semester 4, academic session 2021-22. Published by Dr. A.P.J. Abdul Kalam Technical University (AKTU/UPTU), Lucknow. Free PDF download — no login required.

Course:B.Tech
Semester:Semester 4
Session:2021-22
University:AKTU / UPTU

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Questions Asked in 2021-22

Electrical Machines I (KEE402) — complete question paper

Section AAttempt all q u e s t i o n s i n b r i e f . 2 x 10 = 20
  • a
    From consideration of the various energies involved, draw the model of an electromechanical energy conversion device
  • b
    Why do all practical energy conve rsion devices make use of mag netic field as a coupling medium rather than an electric field? Also, Write the energy balance equation
  • c
    Discuss briefly why dc machine is not started without a starter? 2
  • d
    Define back pitch and front pitch of armature winding in dc ma chine 2
  • e
    What are the factors that affect the speed of the dc motor? 3
  • f
    Which dc motor is used to dr ive cranes? Give reason. 3
  • g
    Why is transformer not used on dc supply? 4
  • h
    The emf per turn of a single-phase transformer 6.6 kV/440 V, 5 0 Hz transformer is approximately 12 V. Calculate the number of turns in the HV and LV windings. i. What are vector groups in 3-phase transformer? 5 j. Compare core type and shell type 3-phase transformers. 5
Section BAttempt any three o f t h e f o l l o w i n g : 10x3=30
  • a
    Show that the magnetic force 𝑓௘ is given by the expression
  • b
    Discuss armature reaction in dc machine. What is the (i) pur pose and (ii) location of inter-poles and compensating winding in a dc machine? Explain with the help of neat sketches
  • c
    Derive out the characteristics of (i) DC shunt motor (ii) DC Series Motor 3
  • d
    The following data were obtained for a 20-kVA, 60-Hz, 2400/2 40-V distribution transformer tested at 50 Hz: Voltage Current Power OC test : 240 1.038 122 (on lv side) SC Test : 61.3 8.03 257 (on hv side) Compute the (i) efficiency at ¾ full-load current (ii) maximum efficiency and the load corresponding to max efficiency at unit y power factor (iii) Secondary terminal voltage at 0.8 power factor whe n the applied input voltage is 2400 V and (iv) voltage regulation at 0.8 pf for lagging and leading load
  • e
    With the help of circuit dia gram describe open-delta connection? Prove that the open delta connection has a kVA rating of 57.7% of the rating of the normal delta-delta connection
Section CAttempt any one part of the following: 10x1=10
  • a
    Derive a relationship between magnetic field energy and co-e nergy for
  • a
    singly excited system
  • b
    For an electromagnetic system, show that the mechanical work done is equal to the area enclosed between the two magnetization curves at open and closed positions of the armature and the ψ-i locus during instantaneous armature movement
  • a
    With the help of neat sketch br iefly (i) the process of commutation and (ii) delayed commutation in a dc machine
  • b
    Derive the EMF equation and Torque equation of dc machine 2
  • a
    With the help of suitable circuit diagrams, explain Armature Control Method and Field Control Method for speed control of DC Series Motor
  • b
    Hopkinson’s test conducted on 2 identical machines gave the following test result: field currents 5 A and 4.2 A, line voltage 230V, m otor armature current 380 A, line currents excluding both the field currents is 50 A. Calculate the efficiency of both machines. Take R a (each machine) =0.02 ohms
  • a
    With the help of circuit diagram explain the procedures of o pen circuit tests and short circuit tests conducted on a single-phase trans former. How parameters of equivalent circuit can be determined from the se tests?
  • b
    A 200 kVA transformer has an efficiency of 98% at full load. If th e maximum efficiency occurs at three quarters of full load, calcu late the efficiency at half load. Assume negligible magnetizing current and power factor of 0.8 at all loads
  • a
    What are the advantages of a bank of three 1-phase transformers over a unit transformer? Discuss the different types of connections em ployed in 3-phase transformers?
  • b
    Enumerate the conditions necessary for two 3-phase transform ers to be connected in parallel. Two single phase transformers, rated 100 0 kVA and 500kVA respectively, are connected in parallel on both HV and LV sides. They have equal voltage ratings of 11kV/400 V and their per unit impedances are (0.02 + j 0.07) and (0.025 +j 0.0875) respectively. What is the largest value of the unity power factor load that can be delivered by the parallel combination at the rated voltage? How is the load shared between the two transformers?

Question text is extracted from the official AKTU question paper PDF above. Hindi translations are omitted — every question is printed in English in the original paper. Last verified: 2026-08-23.

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