B.TechSemester 42024-25Electrical Machines IBEE402

Electrical Machines I (BEE402) - AKTU Question Paper 2024-25

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 2024-25. 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:2024-25

University:AKTU / UPTU

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Questions Asked in 2024-25

Electrical Machines I (BEE402) — complete question paper · 70 marks · 3 Hours

Section AAttempt all q u e s t i o n s i n b r i e f . 0 2 x 7 = 1 4

a
Define Co-energy and explain its physical significance
b
Derive the relation between electrical and mechanical degree u sing the waveform of induced emf in an armature coil
c
Explain the interpoles
d
A series motor cannot be left unloaded, explain using speed-to rque curve
e
Explain the polarity test of single-phase transformer
f
Explain Star/Delta connection in three phase transformers. 5 K 2
g
Give conditions for three para llel operation of three phase transformer

Section BAttempt any three o f t h e f o l l o w i n g : 0 7 x 3 = 2 1

a
Determine the force and torque equation from energy and co-e nergy
b
Describe the process of commutation. Also explain its types and the methods to improve the commutation in DC machines
c
A 250 V dc shunt motor has an armature resistance of 0.5Ω and a field resistance of 250 Ω. When driving a constant torque load at 600 rpm, the motor draws 21 A. What will be the new speed of the motor if an additional 250 Ω resistance is inserted in the field circuit?
d
The maximum efficiency of a 50 kVA, 1100/440 V, 50 Hz transformer is 96%. This occurs at 85% of full load at 0.8 p.f. lagging. Calculate the efficiency of transformer at half load and at 0.6 p.f. lagging
e
What are the methods of speed control of DC motor. Explain W ard Leonard methods of speed control

Section CAttempt any one p a r t o f t h e f o l l o w i n g : 0 7 x 1 = 0 7

a
Derive the torque expression in cylindrical rotor machines
b
Explain the principle of electromechanical energy conversion using suitable block diagram, energy balance equation and energy flow diagram
a
Explain the armature reaction in DC generators using armatur e and field MMF waveforms. Describe the effects of armature reaction?
b
Draw the external characteristics of various types of dc gen erators in one figure on the assumption of same rated terminal voltage and the same rated load current. A 240V, 36kW, dc shunt generator has 500 field turns per pole. On no load, the generated voltage of 240 V is obtained with a field current o f 2 A . F o r maintaining 240 V at full load and at the same speed, the field current required is 3.2 A. Calculate the number of series-field turns per pole r equired for level compounding
a
Justify the need of Starter in DC motors. Explain the constr uction and operation of 4-point starter
b
A 230V DC series motor develops its rated output at 1500rpm while taking 20A. Armature and series field resistances are 0.3 Ω and 0.2 Ω respectively. Neglecting saturation, determine the resistance that must be ad ded to obtain rated torque i) at starting and ii) at 1000 rpm
a
In Open Circuit and Short Circuit Test the following reading were obtained on

230/115Volt, 1kVA 1- phase transformer.

Low voltage side : 100V, 0.26A, 8.3W;
High Voltage side : 18.4V, 5A, 46W;
Determine the equivalent circuit and parameters of transformer.  A l s o
determine the Efficiency and Voltage Regulation at Full load 0.8 pf Lagging

b
What is V-V connection? Show that the open delta connection has a kVA rating of 57.7% of the rating of the normal delta-delta connection
a
Explain Sumpner’s test in transformer with neat diagram. 4 K 3
b
Enlist conditions of paralle l operation of three phase trans formers. Two 150 kVA, single-phase transformers are to be operated in parallel to share
a
load of 240 kW at pf 0.8 lagging. The equivalent leakage impe dances are 1+j3.0Ω for transformer A and 1.2+j3.2Ω for transformer B. Calculate the load shared by each transformer and their operating power factors

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.

Repeated Questions — BEE402

Questions that appeared in more than one session, found by comparing 3 years of Electrical Machines I papers (2023-24, 2024-25, 2025-26)

Give conditions for three para llel operation of three phase transformer

Appeared in: 2023-24 · 2024-25 · 2025-26

What is V-V connection? Show that the open delta connection has a kVA rating of 57.7% of the rating of the normal delta-delta connection

Appeared in: 2023-24 · 2024-25 · 2025-26

Describe the process of commutation. Also explain its types and the methods to improve the commutation in DC machines