logo
  • Home
  • Rank
  • Tests
  • About
  • Training
  • Programming
  • CS
  • IT
  • IS
  • ECE
  • EEE
  • EE
  • Civil
  • Mechanical
  • Chemical
  • Metallurgy
  • Instrumentation
  • Aeronautical
  • Aerospace
  • Biotechnology
  • Agriculture
  • MCA
  • BCA
  • Internship
  • Contact

Electrical Machines Multiple Choice Questions | MCQs | Quiz

Electrical Machines Interview Questions and Answers
Practice Electrical Machines questions and answers for interviews, campus placements, online tests, aptitude tests, quizzes and competitive exams.

Get Started

•   Energy Principles
•   Singly Magnetic System
•   Reluctance Motor
•   Doubly Magnetic System
•   Synchronous Machines
•   Singly Electric Systems
•   Torque Equations
•   Rotating Machines Terms
•   Rotating Magnetic Field-1
•   Rotating Magnetic Field-2
•   Rotating EM - 1
•   Rotating EM - 2
•   Rotating EM - 3
•   Generated Emfs
•   Losses and Efficiency-1
•   Losses and Efficiency-2
•   Machine Ratings
•   Cooling(Loss Dissipation)
•   Machine Applications
•   Commutator Action
•   Armature Generation
•   DC Machines Torque
•   DC Machines Circuits
•   Excitation Methods
•   MMF & Flux Waveforms
•   Compensation Winding
•   DC Machines Testing
•   DC Machine Applications
•   Generator Characteristics
•   Rotating Amplifiers
•   Motors Characteristics
•   DC Motors Basics
•   DC Motors Speed Control
•   DC Motors Magnet
•   EMF Polygon - 1
•   EMF Polygon - 2
•   Non-Salient Machines
•   Distributed Windings
•   Synchronous Machines
•   Flux & MMF Phasors
•   Synchronous Operation
•   Synchronous Controls
•   Salient Pole Machines
•   Characteristics
•   Xd & Xq Measurement
•   Applications
•   Cylindrical Rotor
•   Voltage Regulation
•   Alternator Characteristics
•   Motors Phasor Diagram
•   Motor Power Factor
•   Motors Basics
•   Inductive Impedance - 1
•   Inductive Impedance - 2
•   Efficiency
•   Losses & Efficiency
•   Power & Torque
•   Synchronous Stability
•   Damper Winding
•   Induction Motor
•   Operation Principles
•   MMF Phasors & Waves
•   Rotor Frequency
•   EMF, Current & Power
•   Induction Motor Phasor
•   Equivalent Circuit
•   Circuit Analysis
•   Motor Characteristics
•   Circuit Parameters
•   Three Phase Motor
•   Induction Generator
•   Polyphase Induction
•   Induction Diagrams
•   Polyphase Motors - 1
•   Polyphase Motors - 2
•   Armature Windings
•   Transformer Construction
•   Ideal Two Winding
•   Phasor Diagrams
•   Transformer Circuit
•   Open & Short Circuit Test
•   Voltage Regulation
•   Transformer Efficiency
•   Single Phase
•   Magnetically Coupled
•   Three Phase Transformer
•   Autotransformers

« Prev Page
Next Page »

Electrical Machines Questions and Answers – Rotating Magnetic Field – 2

Posted on May 19, 2017 by Manish

This set of Electrical Machines Multiple Choice Questions & Answers (MCQs) focuses on “Rotating Magnetic Field – 2”.

1. If F1 is the constant amplitude of fundamental rotating MMF wave, the for the space harmonics of order 6K-1 (where K=1,2,3….), the harmonic MMF wave is of _____________
a) Constant amplitude and stationary in space
b) Constant amplitude and rotates along F1
c) Varying amplitude and rotates along F1
d) Constant amplitude and rotates against F1
View Answer

Answer: b
Explanation: Space harmonics of the order of 6K-1(5,11,17,…) have their constant amplitude equal to 1/(6K-1)F1 and rotate in the direction of fundamental component F1 at a speed of 1/(6K+1) of the fundamental synchronous speed.
advertisement

2. Which of the following harmonics are present in the resultant MMF produced by 3 phase currents flowing in the 3 phase windings?
a) Triplen harmonics (3K), where K is an integer
b) 6K+1 harmonics only, where K is an integer
c) 6K-1 harmonics only, where K is an integer
d) 6k+1 and 6K-1 harmonics, where K is an integer
View Answer

Answer: d
Explanation: Space harmonics of the order 3,9,15,… i.e, triplen harmonics are absent.

3. When a single-phase winding is excited by an alternating current, then which of the following statements are correct?
a) It produces one stationary MMF wave
b) Produced MMF wave pulsates along its magnetic axis
c) It doesn’t produce two counter rotating MMF wave
d) All of the mentioned
View Answer

Answer: d
Explanation: It is the decomposition of the MMF of a single phase winding into two counter rotating MMF waves, but are not actually produced and only one stationary MMF wave pulsating along its magnetic axis is produced.

4. What does the space angle α in the equation Fr(α,t)=3/2Fmcos(α-ωt) for MMF produced when 3-phase balanced windings excited by three phase balanced currents represent?
a) MMF wave at any moment is sinusoidally distributed in space
b) Entire MMF waveform is travelling at (constant angular speed) synchronous speed
c) MMF wave is of constant amplitude
d) None of the mentioned
View Answer

Answer: a
Explanation: The space angle α means that MMF wave at any moment is sinusoidally distributed in space along the air-gap periphery.
advertisement

5. Three phase voltages are applied to the three windings of an electrical machine. If any two supply terminals are interchanged, then the rotating MMF wave _____________
a) Direction reverses, amplitude alters
b) Direction reverses, amplitude unaltered
c) Direction remains same, amplitude alters
d) Direction remains same, amplitude unaltered
View Answer

Answer: b
Explanation: The direction of rotating MMF wave is reversed, though its amplitude remains unaltered.

6. The rotating MMF wave of constant amplitude can be produced, only if the time angle displacement between currents is _____________
a) Less than the space angle displacement between winding axis
b) More than the space angle displacement between winding axis
c) Equal to the space angle displacement between winding axis
d) Any of the mentioned
View Answer

Answer: c
Explanation: If the time angle displacement between currents and space angle displacement between winding axis are not equal, the magnitude of resultant MMF wave is always zero.

7. A 3 phase star connected winding is fed from symmetrical 3 phase supply with their neutrals connected together. If one of the 3 supply lines gets disconnected, then the revolving MMF wave will have a ___________
a) Constant amplitude but sub synchronous speed
b) Varying amplitude but synchronous speed
c) Constant amplitude but super synchronous speed
d) Varying speed and a speed fluctuating around the synchronous speed
View Answer

Answer: d
Explanation: With one supply phase disconnected, a rotating MMF wave of varying amplitude is produced, but at a speed fluctuating around the synchronous speed.
advertisement

8. In case of the 3 phase winding with delta or star connection without neutral, if one of the supply lines gets disconnected, then the MMF becomes __________
a) Stationary and pulsating
b) Rotating with synchronous speed
c) Rotating with sub synchronous speed
d) Rotating with super synchronous speed
View Answer

Answer: a
Explanation: Disconnection of one of the supply leads, results in single-phase operation of the machine.

9. If φm is the maximum value of flux due to any one phase, then resultant flux in 2 phase and 3 phase AC machines would respectively be given by _________
a) φm and 1.5φm, both rotating
b) φm and 1.5φm, both stand still
c) φm stand still and 1.5φm rotating
d) 1.5φm and 2φm, both rotating
View Answer

Answer: a
Explanation: In a 2 phase and 3 phase AC machine, rotating MMF is produced with magnitudes of φm and 3/2φm.

Sanfoundry Global Education & Learning Series – Electrical Machines.
To practice all areas of Electrical Machines, here is complete set of 1000+ Multiple Choice Questions and Answers.

« Prev Page - Electrical Machines Questions and Answers – Rotating Magnetic Field – 1
» Next Page - Electrical Machines Questions and Answers – Constructional Features of Rotating Electrical Machines-1

« Electrical Machines Questions and Answers – Rotating Magnetic Field – 1
Electrical Machines Questions and Answers – Constructional Features of Rotating Electrical Machines-1 »
advertisement

Deep Dive @ Sanfoundry:

  1. Analog Communications Questions and Answers
  2. Electrical Measurements Questions and Answers
  3. Electrical Engineering Questions and Answers
  4. Electrical & Electronics Engineering Questions and Answers
  5. Theory of Machines Questions and Answers
  6. Basic Electrical Engineering Questions and Answers
  7. Hydraulic Machines Questions and Answers
  8. DC Machines Questions and Answers
  9. Design of Electrical Machines Questions and Answers
  10. Electrical Machines Questions and Answers
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer and SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage & Cluster Administration, Advanced C Programming, SAN Storage Technologies, SCSI Internals and Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him below:
LinkedIn | Facebook | Twitter | Google+

Best Careers

Developer Tracks
SAN Developer
Linux Kernel Developer
Linux Driver Developer
Linux Network Developer

Live Training Photos
Mentoring
Software Productivity
GDB Assignment
Sanfoundry is No. 1 choice for Deep Hands-ON Trainings in SAN, Linux & C, Kernel Programming. Our Founder has trained employees of almost all Top Companies in India such as VMware, Citrix, Oracle, Motorola, Ericsson, Aricent, HP, Intuit, Microsoft, Cisco, SAP Labs, Siemens, Symantec, Redhat, Chelsio, Cavium, ST-Micro, Samsung, LG-Soft, Wipro, TCS, HCL, IBM, Accenture, HSBC, Mphasis, Tata-Elxsi, Tata VSNL, Mindtree, Cognizant and Startups.

Best Trainings

SAN I - Technology
SAN II - Admin
Linux Fundamentals
Advanced C Training
Linux-C Debugging
System Programming
Network Programming
Linux Threads
Kernel Programming
Kernel Debugging
Linux Device Drivers

Best Reference Books

Computer Science Books
Algorithm & Programming Books
Electronics Engineering Books
Electrical Engineering Books
Chemical Engineering Books
Civil Engineering Books
Mechanical Engineering Books
Industrial Engineering Books
Instrumentation Engg Books
Metallurgical Engineering Books
All Stream Best Books

Questions and Answers

1000 C Questions & Answers
1000 C++ Questions & Answers
1000 C# Questions & Answers
1000 Java Questions & Answers
1000 Linux Questions & Answers
1000 Python Questions
1000 PHP Questions & Answers
1000 Hadoop Questions
Cloud Computing Questions
Computer Science Questions
All Stream Questions & Answers

India Internships

Computer Science Internships
Instrumentation Internships
Electronics Internships
Electrical Internships
Mechanical Internships
Industrial Internships
Systems Internships
Chemical Internships
Civil Internships
IT Internships
All Stream Internships

About Sanfoundry

About Us
Copyright
Terms
Privacy Policy
Jobs
Bangalore Training
Online Training
Developers Track
Mentoring Sessions
Contact Us
Sitemap
© 2011 Sanfoundry. All Rights Reserved.