Electrical Machine & Power Control B.E Question Paper : jaduniv.edu.in

Name of the University : Jadavpur University
Department : Power Engineering
Degree : B.E
Subject Name : Power Transducers Technology
Year/Sem : III/II
Website : jaduniv.edu.in
Document Type : Model Question Paper

Download Model/Sample Question Paper : https://www.pdfquestion.in/uploads/dspace.jdvu.ac.in/6148-Electrical%20Machine%20&%20POwer%20Control.pdf

Jadavpur Electrical Machine & Power Control Question

Bachelor Of Power Engineering Examination, 2013 :
(3rd Year 2nd Semester)
(Use separate answer script for each part)
PART:(50marks)

Related : Jadavpur University Power Transducers Technology M.E Question Paper : www.pdfquestion.in/6146.html

Model Questions

Part – I

Answer any three questions :(2 marks for neatness)
1. a) What is electrical drive? What are the different components of an electrical drive system2+6 and explain their functions.
b) What are the speed-toque conventions for drive system? Describe the four quadrant2+6 operation of a motor driving a hoist load.

2. a) What is steady state stability of electrical drive? Derive the condition for steady state stability.2+6
b) A 480V, 3-ph induction motor has rated speed at full load of 1120 rpm, stator resistance of 1 ohm, rotor resistance referred to stator of 1 ohm and equivalent winding reactance of 5 ohm. The inertia of the motor is 4 Nm-sec2/rad.Compute the starting time of the motor at no-load and at full voltage and frequency.

3.a) What are the factors influencing the choice of electrical drives? 8
b-) Describe how the speed of a separately'”excited dc motor is controlled through the use of a three phase full-converter. Discuss how two quadrant drive can be obtained from this6+4 scheme.

4. a) Describe the operation of single phase semi-controlled converter fed separately excited dc motor in both continuous and discontinuous modes. 8
b) The speed of a separately excited dc motor is controlled by means of 3-ph semi-converter from a 3-ph, 415 V, 50 Hz supply. The motor constants are: inductance 10mH, resistance8 0.9 ohm and armature constant 1.5 V/rad/s (Nm/A). Calculate the speed of this motor at a torque of 50 Nm when the converter is fired at 45°. Neglect losses in the converter.

5.a) Derive appropriate expression to obtain speed-torque characteristic of static Kramer drive.8
a) A static Kramer drive is used for the speed control of a 4-pole SRIM fed from 3-ph, 415 V, 50 Hz supply. The inverter is connected directly to the supply. If the motor is required to operate at 1200 rpm, find the firing advance angle of the inverter. Voltage across the open circuited slip rings at standstill is 700 V. Allow a voltage drop of 0.7 V and 1.5 V across each of the diodes and thyristors respectively. Inductor drop is neglected.

PART – II

Answer any three questions.
(2 marks for neatness)
1.Figure 1 shows the one line diagram of a 3-bus power system with generation at bus 1 and 3. The voltage at bus 1 is V; =1.025LOo pu. The voltage magnitude at bus 3 is fixed at 1.03 pu with a real power generation of 300 MW. A load consisting of 400 MW and 200 MYAR is taken from bus 2. The line impedences are marked inpu on a 100MYA base. Computethe bus admittancematrix. Using Gauss-Seidelmethod and initial estimates of V/o) =1.0 + jO and V/O) =1.03 + jO and keepinglV31= 1.03pu, determine the phasor values of V2 and V3. 16
V1= 1.025LO° 400MW 200 MVar
Slack bus

2.a.Derive swing equation. 4
b. A cylindrical rotor synchronous motor, connected to an infinite bus, is working under full load conditions with a load angle ofJO°.
(i) If the shaft load is suddenly increased to 1.5 times the full load, determine whether or not the synchronism is maintained.
(ii) Determine the maximum additional safe load that can be suddenly thrown on to the motor shaft. 12

3. a. Draw the complete block diagram of load frequency control of an isolated power system and obtain the expression for steady state change in the system frequency for a sudden change in load demand.Also draw the steady state load – frequency characteristic of the same. 8
(b) Two generators rated at 400 MW and 600 MW are operating in parallel. The drop characteristics of their governors are 3 % and 4% respectively from no load to full load. Assuming that the generators are operating at 50 Hz at no load, how would a load of 1000 MW be shared between them? What will be the system frequency at this load? Assume linear governor operation. .’ 8

5. Write short notes on any two of the followings: 2 x 8
1. EqualArea Criterion.
2. Unit Commitment.
3. Staticexcitationsystemof synchronousgenerator.
4. Modelingof turbinespeedgoverningsystem.