DieselShip's Online Content Library

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)

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.

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/ship diagrams.

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.