DieselShip's Online Content Library

Q3. a) Write a short note on the principle of operation of induction motors (8)

b) What is slip for an induction motor? (4)

c) If a 4-pole motor is supplied at 60Hz and runs with a slip of 5%. What is the actual rotor speed? (4)

Q5. a) Briefly explain the principle of Operation of Induction Motors (4)

b) What is slip for an induction motor? (4)

c) Draw a simple ladder logic diagram of star delta starting of an induction motor. (8)

Q2. Explain the methods used to control the speed of a 3 Phase induction motors. Draw and Explain a Variable Frequency Drive used for optimization of energy efficiency of auxiliary machineries on board vessels.

Q5. What is soft starting of an Induction motor? Describe with a circuit using thyristors used for soft starting. Discuss its advantages and dis-advantages. (16)

Q3. Explain the matching of an induction electric motor to a pump required for main circulating duty, with the aid of pump characteristic and torque/slip diagrams. (16)

Q4. Explain the effect of reduced voltage on standard squirrel cage motors with respect to EACH of the following:

(i) Burn out; (ii) Starting current; (iii) Starting torque; (iv) Speed.

Q1. a) Explain the term single phasing as applied to poly phase induction motors. (4)

b) State the likely causes of single phasing and the consequences if motors are not adequately protected. (6)

c) Describe with the aid of sketches THREE methods for motor protection should single phasing occur. (6)

Q5. Write short notes on

a) short circuit protection to Induction motors (8)

b) Overload protection to induction motors (8)

Q3. What is soft starting of an Induction Motor? Describe with a circuit using thyristors used for soft starting. Discuss its advantages and disadvantages. (16)

Q3. With reference to squirrel cage, induction, electric motors:

A. Describe the construction of such a motor. (6)

B. Sketch the torque against speed curve of such a motor. (5)

C. Describe a method employed by a retrofitted device used to improve the part load performance of an induction motor. (5)

Q1. a) Briefly explain the principle of operation of Induction Motors (4)

b) What is slip for an induction motor? (4)

c) Draw a simple ladder logic diagram of star delta starting of an induction motor. (8)

Q1. Direct online starting for large induction motors such as those for bow thrust units, may not be viable.

a) State the reasons for this. (5)

b) Sketch a starting system that may be used for such motors. (6)

c) Describe the starting method sketched in (a, b). (6)