SESSIONAL QUESTION PAPER FOR ACM SUBJECT

ELECTRICAL ENGG. DEPT.

             Course Code: EE- 5G   (First Sessional Exam 2015-16)     

                                   Subject: ACM    Marks: 25 M   Time: 1 hr

1    1)      Solve any THREE        (3 X 3 = 09m)

           a) Explain the working principal of 3-Ø induction motor.

           b) Draw block diagram showing power stages of a 3-Ø I.M.

                   c)  Explain why 3-Ø I.M. is called as a asynchronous motor.

            d) Prove that rotor cu loss in I. M. is slip times rotor Input.

 

2      2)      Solve any Two             (4 X 2= 08 M)

            a) Draw & explain torque-slip characteristics of 3-Ø I. M.

b) State the functions of following parts of an I.M. (i) Slip rings (ii) Fan (iii) Brushes (iv) Frame.

c) A 37 KW (o/p), 4 pole, 50 Hz, 3-Ø I.M. has a friction & windage loss of 20 N-m. The stator losses equal the rotor cu loss. Calculate I/p power to the stator winding when the 3-Ø I. M. is delivering full load O/p at 1440 RPM.

                                                                                                  

3       3)      Solve any Two            (4 X 2= 08 M)

a) Derive the torque of 3-Ø I.M.

b) Explain with neat sketches the production of rotating Magnetic field in 3-Ø I.M.

c)  3-Ø, 50 Hz, 4 pole, I. M. has a slip of 4% calculate (1) Speed of motor, (2) freq. of rotor emf if the rotor has a resistance of 1 Ω & standstill reactance of 4 Ω. Calculate P.F. at (i) Standstill condition, (ii) Speed of 1440 RPM.