Name of the College : Mahatma Gandhi University
Department : Electrical and Electronics Engineering
Subject Code/Name : MEEID 104/Electric Drives
Sem : I
Website : mgu.ac.in
Document Type : Model Question Paper
Download Model/Sample Question Paper : https://www.pdfquestion.in/uploads/mgu.ac.in/5047-MEEID%20104%20Electric%20Drives.doc
MGU Electric Drives Question Paper
M.TECH. Degree Examination :
Model question paper :
First Semester :
Related : MGU MEEID103 Dynamics of Electrical Machines M.Tech Model Question Paper : www.pdfquestion.in/5046.html
Branch: Electrical and Electronics Engg
Specialization : Industrial Drives and Control
MEEID 104 : Electric Drives
(Regular/Supplementary – 2013 Admission Onwards)
Time : Three Hours
Maximum : 100Marks
Answer All Questions :
1 a) What is load equalization? Derive the moment of inertia of the flywheel (8 marks)
b) What are active and Passive loads? Draw the speed torque characteristics for constant power load applications (7 marks)
c) A motor equipped with a flywheel has to supply a load torque of 600N-m for 10sec followed by a no load period long enough for the flywheel to regain its full speed. It is desired to limit the motor torque to 450 N-m.
What should be the moment of inertia of the flywheel? The no load speed of the motor is 600 rpm and it has a slip of 8% at torque of 400N-m. Assume the motor speed –torque characteristics to be a straight line in the range of operation. Motor has an inertia of 10kg- m2. (10 marks)
OR
2 a) Derive the condition for steady state stability of a motor load system. (8 marks)
b) State and explain essential parts of electrical drives. What are the functions of a power modulator? (7 marks)
c) A weight of 500kg is lifted up at a uniform speed of 1.5m/s by a winch driven by a motor running at a speed of 1000 rpm. The moments of inertia of the motor and winch are 0.5 and 0.3 kg- m2 respectively.
Calculate the motor torque and equivalent moment of inertia referred to the motor shaft. In the absence of weight, motor develops a torque of 100 N-m when running at 1000 rpm. (10 marks)
3 a) Draw the block diagram of speed control of DC drive below and above base speed. Explain the working . (10 marks)
b) Explain motoring and braking operation of DC series motor using choppers (10 marks)
c) How fourth quadrant operation is possible with FCR control of SEDC motor. Why it is not possible with DC series motor. (5 marks)
OR
4 a) Draw and Explain the power circuit of a single phase fully controlled rectifier control of a dc separately excited motor. Also draw the waveform at discontinuous mode and speed – torque characteristics (10 marks)
b) Derive the equation for critical speed of single phase fully controlled rectifier control of a dc separately excited motor. (15 marks)
5 a) Draw and explain the operation of CSI fed induction motor. Derive the torque equation. Compare VSI and CSI induction motor drives. (7 marks)
b) Draw and explain the operation the closed loop scheme of induction motor with voltage source inverter (8 marks)
c) A 440 V, 3-phase, 50 Hz, 6-pole, 945 rpm, delta connected induction motor has following parameters referred to the stator Rs = 2.0 Rr’ = 2.0 , Xs = 3 Xr’ = 4 . When driving a fan load at rated voltage it runs at rated speed.
The motor speed is controlled by stator voltage control, Determine (i)Motor terminal voltage, current and torque at 800 rpm. (ii) Motor speed, current and torque for the terminal voltage of 280 V. (10 marks)
OR
6 a) What are advantages of PWM Inverters. Derive the expression for rms output voltage of multiple PWM inverter. . (6 marks)
b) Sketch the power flow diagram of WRIM with modern scherbius drive scheme. Explain the operation with relevant equation. Derive the torque equation (9 marks)
c) A Y- connected squirrel cage induction motor has following ratings and parameters:400V,50Hz,4-pole,1370rpm,Rs=2?,Rr’=3 ? ,Xs=Xr’=3.5?.Motor is controlled by a voltage source inverter at constant v/f ratio. Inverter allows frequency variation from 10to 50Hz.
Calculate the starting torque and current of this drive as a ratio of their values when motor is started at rated voltage and frequency? (10 marks)
7 a) Derive the torque equation of salient pole wound field synchronous motor. Draw the speed torque curve. (10 marks)
b) Explain the concept of variable frequency control of synchronous motor drives. Draw the speed torque curve. (6 marks)
c) Draw the block diagram and explain the closed loop control of synchronous motor drive under true synchronous mode (9 marks)
OR
8 a) Explain the open loop control of self controlled synchronous motor drive employing load commutated thyristor. Derive the expression for phase current. (15 marks)
b) Draw the closed loop block diagram of self controlled synchronous motor drive and explain the operation (10 marks)