Electrical Machines - May 2016

MU Electronics Engineering (Semester 4)

Total marks: --
Total time: -- INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

Solve any three question Q1.(a,b,c,d)

1(b) Explain the construction of permanent magnet syhronous motor. 5 marks

1(c) Draw and explain block diagram V/f control using converter- inverter scheme for 3 phase induction motor. 5 marks

1(d) Explain back emf equation of dc motor. 5 marks

2(a) Explain the principle of operation of capacitor start and capacitor run single phase induction along with slip-torque charateristics and applications. 5 marks

2(b) Explain construction and working of multistack variable reluctance stepper motor. 5 marks

3(a) A 4 pole 3 phase 50Hz star connected induction motor has ful load slip of 6% calculate full load speed of the motor. 5 marks

3(b) Explain double field revolving theory in single phase induction motor. 5 marks

4(a) Classify the brushless DC motor and explain in detail unipolar brushless Dc motor. 5 marks

4(b) A 800W,
115V,
60Hz capacitor start motor draw 13.8 A from the supply at rated load if the efficiency is 70% and rated speed is 1800 rpm, Calculate
i) Input power at rated load
ii) Power factor at rated load
iii) Rated motor horse power 5 marks

5(a) Explain diffefrent speed control methods of DC short motor. 5 marks

5(b) Explain construction and working of 3 phase squirrel cage induction motor. 5 marks

6(a) Write short note on
Advantages of brushles DC motor. 5 marks

6(b) Three point starter of DC shunt motor. 5 marks

6(c) Starting methods of 3 phase induction motor. 5 marks