MET MEO Class 2 Written Question (APR 2023)

EXAMINATION OF MARINE ENGINEER OFFICER

MARINE ELECTRO – TECHNOLOGY

M.E.O. CLASS II

TIME  - 3 HOURS  Total Marks - 100

Q1. A. Give a brief outline of the care and maintenance that should be given to the stator and rotor of an A.C. generator;

B. Explain what is likely to occur if the driving power of one A.C. generator suddenly fails when two generators are running in parallel. What safety devices are usually provided for such events?

Q2. Compare methods of obtaining speed regulation of three-phase induction motors generally used in tankers by means of:

A. Rotor resistance; B. Cascade system; C. Pole-changing. Give examples where each system may be employed with advantage.

Q3. A. Explain how the efficiency and regulation of a transformer can be assessed by open circuit and short circuit tests?

B. What is meant by equivalent resistance?

Q4. With reference to a 3 speed a.c. cage motor driven cargo winch:

A. Sketch a circuit diagram for a pole change motor;

B. Describe how speed change and braking are achieved.

Q5. With reference to the condition monitoring of electrical machinery:

A. State TWO important parameters that may be recorded;

B. Explain how the parameters are measured and what defects may be revealed.

Q6. (a). Explain the significance of the root- mean- square value of an alternating current or voltage waveform; Define the form factor of such a wave form.

(b). A total load of 8000 kW at 0.8 power factor is supplied by two alternators in parallel. One alternator supplies 6000 kW at 0.9 power factor. Find the kVA rating of the other alternator and the power factor.

Q7. A. Electric motors contain a stationary member as well as a rotating member. For each of the following machines, identify in which part of the motor three field winding and the armature winding are located: three phase induction motor, three phase synchronous motor, d.c. motor.

B. A 220 V, d.c. shunt motor has an armature resistance of 0.5 ohm and an armature current of 40 A on full load. Determine the reduction in flux necessary for a 50 per cent reduction in speed. The torque for both conditions can be assumed to remain constant.

Q8. A. Show how the power that is transferred across the air gap of the three-phase induction motor is represented. Explain the terms. What portion of this is useful power?

B. A 440 load of 400 KW at 0.8 (lagging) power factor is jointly supplied by two alternator A and B. The KW load on A is 150 KW and the KVAr load on B is 150 KVAr (lagging). Determine the KW load on

B, the KVAr

Q10. A. (i) What is direct-connected alternator?

(ii) How is a direct-connected exciter arranged in an alternator?

B. Find the synchronous impedance reactance of an alternator in which a given field current produces an armature current of 200 A on short circuit and a generated e.m.f. of 50V on open circuit. The armature resistance is 0.1 ohm. To what induced voltage must the alternator be excited if it is to deliver a load of 100A at a p.f of 0.8 lagging, with a terminal voltage of 200 V.