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Electrical Machines Exam Paper: B. Tech ECE 4th Semester, 2018-2019, Essays (university) of Machine Design

Malaviya National Institute of TechnologyMachine Design

describe the content plz. its assignment and notes of electrical machines

Typology: Essays (university)

2019/2020

Uploaded on 07/13/2020

kamran-razi
kamran-razi 🇮🇳

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bg1
Session: 2018-2019 (Spring) Class: B. Tech Branch: ECE Semester: 4th Exam: Major
Course Code: ELE-405 Course Name: Electrical Machines Total Time: 3 hours Max Marks: 60
Course Objectives:
CO1: To study transformer construction, operation, various tests, find efficiency & voltage regulation.
CO2: Study about DC machines, operation, performance, applications, recent advancements.
CO3: To study operation, performance and application of induction machines.
CO4: Study of alternator and synchronous motor.
Note: Attempt Any Four Questions out of Five Questions.
1. (a) With the help of phasor diagram, explain the operation of a transformer under no load and load
conditions. (7M) [CO1]
(b) A 4400 V, 50-Hz transformer has a hysteresis loss of 1200 W, eddy current loss of 1800 W and
full-load copper loss of 4000 W. If the transformer is supplied at 6600 V, 75-Hz. What will be the
losses? (8M) [CO1]
2. (a) A 250V shunt motor runs at 1000 rpm at no load and takes 8A. The total armature and shunt field
resistances are 0.2 and 250 ohms respectively. Calculate the speed when loaded and taking 50A.
Assume the flux to be constant. (7M) [CO2]
(b) A 440V, 3-phase, 8 pole, 50 Hz, 40kW, star connected three phase induction motor has the
following parameters:
Stator resistance= 0.1 Ω, stator reactance = 0.4 Ω
Equivalent rotor resistance referred to stator = 0.15 Ω
Equivalent rotor reactance referred to stator = 0.44 Ω
The stator core loss is 1250W while mechanical loss is 1000W. It draws a no load current of 20A
at a p.f. of 0.09 lagging. While running at a speed of 727.5rpm. Calculate,
i) Input line current and p.f.
ii) Torque developed
iii) Output power and
iv) Efficiency.
Use approximate equivalent circuit. (8M) [CO3]
3. (a) Explain the principle of production of rotating magnetic field in a 3-phase induction motor.
(7M) [CO3]
(b) A 10 kW, 400 V, 3-phase, 4 pole, 50 Hz delta connected induction motor is running at no load
with a line current of 8 A and an input power of 660 W. At full load, line current is 18 A and
input power is 11.20 kW. Stator effective resistance per phase is 1.2 Ω and friction, windage loss
is 420 W. For negligible rotor ohmic losses at no load, calculate (i) stator core loss (ii) Slip at full
load (iii) total rotor ohmic losses at full load (iv) full load speed. (8M) [CO3]
National Institute of Technology-Srinagar
Hazratbal Srinagar-190006, Kashmir (J&K)
Department of Electrical Engineering
pf2

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Download Electrical Machines Exam Paper: B. Tech ECE 4th Semester, 2018-2019 and more Essays (university) Machine Design in PDF only on Docsity!

Session: 2018 - 2019 (Spring) Class: B. Tech Branch: ECE Semester: 4 th^ Exam: Major Course Code: ELE- 405 Course Name: Electrical Machines Total Time: 3 hours Max Marks: 60 Course Objectives: CO1: To study transformer construction, operation, various tests, find efficiency & voltage regulation. CO2: Study about DC machines, operation, performance, applications, recent advancements. CO3: To study operation, performance and application of induction machines. CO4: Study of alternator and synchronous motor.

Note: Attempt Any Four Questions out of Five Questions.

  1. (a) With the help of phasor diagram, explain the operation of a transformer under no load and load conditions. ( 7 M) [CO1] (b) A 4400 V, 50-Hz transformer has a hysteresis loss of 1200 W, eddy current loss of 1800 W and full-load copper loss of 4000 W. If the transformer is supplied at 6600 V, 75-Hz. What will be the losses? ( 8 M) [CO1]
  2. (a) A 250V shunt motor runs at 1000 rpm at no load and takes 8A. The total armature and shunt field resistances are 0.2 and 250 ohms respectively. Calculate the speed when loaded and taking 50A. Assume the flux to be constant. ( 7 M) [CO 2 ] (b) A 440V, 3-phase, 8 pole, 50 Hz, 40kW, star connected three phase induction motor has the following parameters: Stator resistance= 0.1 Ω, stator reactance = 0.4 Ω Equivalent rotor resistance referred to stator = 0.15 Ω Equivalent rotor reactance referred to stator = 0.44 Ω The stator core loss is 1250W while mechanical loss is 1000W. It draws a no load current of 20A at a p.f. of 0.09 lagging. While running at a speed of 727.5rpm. Calculate, i) Input line current and p.f. ii) Torque developed iii) Output power and iv) Efficiency. Use approximate equivalent circuit. ( 8 M) [CO 3 ]
  3. (a) Explain the principle of production of rotating magnetic field in a 3-phase induction motor. ( 7 M) [CO 3 ] (b) A 10 kW, 400 V, 3-phase, 4 pole, 50 Hz delta connected induction motor is running at no load with a line current of 8 A and an input power of 660 W. At full load, line current is 18 A and input power is 11.20 kW. Stator effective resistance per phase is 1.2 Ω and friction, windage loss is 420 W. For negligible rotor ohmic losses at no load, calculate (i) stator core loss (ii) Slip at full load (iii) total rotor ohmic losses at full load (iv) full load speed. ( 8 M) [CO 3 ]

National Institute of Technology-Srinagar

Hazratbal Srinagar- 190006 , Kashmir (J&K)

Department of Electrical Engineering

  1. (a) Mention and Discuss applications of synchronous motor, stepper motor and universal motor. ( 7 M) [CO 4 ] (b) A 20 kW, 200V shunt generator has an armature resistance of 0.05 ohms and a shunt field resistance of 200 ohms. Caculate the power developed in the armature when it delivers rated output. ( 8 M) [CO 2 ]
  2. (a) With the help of phasor diagram, explain the operation of an Alternator. Also explain armature reaction and its effect on operation of alternator. ( 7 M) [CO4] (b) A single phase 440/220 V, 5 kVA, 50 Hz transformer, draws a no-load current of 0.8A at p.f. of 0.25 lag on h.v. side. Determine the magnetizing component, coreloss component, emf per turn on either side and the primary current when the secondary current is 18A at a p.f. of 0.9 lag. ( 8 M) [CO 1 ]

[THE END]