Electrical Machines - II

By Prof. Tapas Kumar Bhattacharya   |   IIT Kharagpur
Learners enrolled: 10491
The course will begin with explaining basic underlying principles of working of various types of electrical rotating machines. The conditions to be fulfilled for the steady production of electromagnetic torque (Te).Motoring and generating mode of operation. Primary focus will be on the operation of 3-phase induction machine, single phase induction motor,and synchronous machines.A fair knowledge of distributed windings is essential in order to understand the working of rotating machines more effectively – few lectures will be devoted on this topic. Concept of electrical and mechanical angles will be explained.Nature of magnetic flux distribution along the air-gap of a rotating machine will be discussed.Clear concept of Rotating magnetic field is so important in understanding the operation of induction and synchronous machines.For each of this machine equivalent circuit will be derived and then used to derive expression for the torque. Starting, speed control and electrical braking of the motors will be discussed. Although main focus will be on the steady state performance analysis, few cases of important transient analysis will be discussed. Students will be motivated to solve numerical problems logically and efficiently.

INTENDED AUDIENCE  : UG Electrical Engineering as core subject.UG Mechanical and Mining Engineering as Elective subject.
PRE-REQUISITES   : Basic Electrical Technology: Circuit analysis, principle of working oftransformer and its equivalent circuit representation.
Course Status : Completed
Course Type : Core
Duration : 12 weeks
Start Date : 27 Jan 2020
End Date : 17 Apr 2020
Exam Date : 25 Apr 2020 IST
Enrollment Ends : 03 Feb 2020
Category :
  • Electrical, Electronics and Communications Engineering
Credit Points : 3
Level : Undergraduate

Page Visits

Course layout

Week 1  :  Brief review of transformer. Rotating machine :generalconstructional features. Conditions for steady production ofelectromagnetic torque. Torque production can be explained interms of interaction of two sets of magnetic poles – one producedby stator coil current and the other by rotor coil currents.
Week 2  :  MMF and flux density distribution along the air-gap of a rotatingmachine by a single coil and by multiple coils. Basic winding termsand elementary balanced 3-phase winding. Idea of electrical andmechanical angle.
Week 3  :   Production of rotating field by a 3-phase winding – iits speed anddirection of rotation and its far reaching implications.
Week 4  :  The expression of induced voltage in a coil when it moves relativeto a field distribution – its rms value and frequency.
Week 5  : Types and constructional features of 3-phase induction motor. Slipand its importance. Development of equivalent circuit of the motorwhen it runs with a slip. Getting expression for torque in terms ofequivalent circuit parameters and supply voltage.
Week 6  : Typical torque slip characteristic. Fixing operating point when loadtorque is present. Modification of the torque -slip characteristic byvarying rotor resistance, supply voltage and frequency.
Week 7  :  Estimation of equivalent circuit parameters from no load and locked(blocked) rotor tests. Problem solving.
Week 8  :  Single phase induction motor: double revolving field theory anddevelopment of equivalent circuit and expression for torque..Torque-slip characteristic. Expression for starting torque inpresence of auxiliary winding. Estimation of starting capacitance forauxiliary coil using concept of phase splitting.
Week 9  :  Synchronous machine: Types and constructional features . EMFequation and concept of synchronous reactance. Synchronising anincoming generator (alternator) to the bus. Phasor diagram asgenerator. Regulation. Effect of excitation variation when generatoris connected to bus. Power-angle characteristic. Steady statestabilty limit.
Week 10  :  Synchronous machine connected to bus and operating as motor .Phasor diagram under various operating conditions. Effect ofexcitation variation.
Week 11  :  Salient pole synchronous machine : concept of direct axis andquadrature axis reactances. Phasor diagrams under various operating conditions both for motoring and generating mode
Week 12  :  Swing equation under dynamic condition. Equal area criteria.Steady state and transient stability limits.

Books and references

1.Electric Machinery Fundamentals 4th Edition by Stephen Chapman 2. Electrical Machinery 7th Edition P. S. Bimbhra 3. Electric Machines and Power System by Del Toro.

Instructor bio

Prof. Tapas Kumar Bhattacharya

IIT Kharagpur
Tapas Kumar Bhattacharya has over thirty years of teaching experince at IIT Kharagpur. Taught signals & system core course at IIT Kharagpur several times.Area of research interest is in the field of electrical machines and special electrical machines and circuits..

Course certificate

• The course is free to enroll and learn from. But if you want a certificate, you have to register and write the proctored exam conducted by us in person at any of the designated exam centres.
• The exam is optional for a fee of Rs 1000/- (Rupees one thousand only).
• Date and Time of Exams: 25th April 2020, Morning session 9am to 12 noon; Afternoon Session 2pm to 5pm.
• Registration url: Announcements will be made when the registration form is open for registrations.
• The online registration form has to be filled and the certification exam fee needs to be paid. More details will be made available when the exam registration form is published. If there are any changes, it will be mentioned then.
• Please check the form for more details on the cities where the exams will be held, the conditions you agree to when you fill the form etc.

• Average assignment score = 25% of average of best 8 assignments out of the total 12 assignments
 given in the course. 
• Exam score = 75% of the proctored certification exam score out of 100
• Final score = Average assignment score + Exam score

• If one of the 2 criteria is not met, you will not get the certificate even if the Final score >= 40/100.
• Certificate will have your name, photograph and the score in the final exam with the breakup.It will have the logos of NPTEL and IIT Kharagpur. It will be e-verifiable at nptel.ac.in/noc.
• Only the e-certificate will be made available. Hard copies will not be dispatched.

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