Frequently asked written questions - Topic wise Segregation of ETO written questions- UPDATED ON APRIL 2022

Subject wise written questions-ETO

Basic Electrical Engineering

1. (a) What has the greater equivalent resistance: two equal capacitors in series or in parallel? Explain with reasons?

(b) A circuit has a resistance of 3 ohms and an inductance of 0.01 H. The voltage across its ends is 60V and the frequency is 50Hz. Calculate (a) the impedance

(b) the power factor (c) the power absorbed. (16 marks)

2. A coil having a resistance of 10Ω and an inductance of 0.15H is connected in series with a capacitor across a 100V, 50Hz supply. If the current and the voltage are in phase what will be the value of the current in the circuit and the voltage drop across the coil?

3. Explain the significance of the Root Mean Square (RMS) value of an alternating current or voltage waveform. Define the form factor of such a waveform.

DC machine

1. Two 220V D.C. generators each having linear external characteristics operated in parallel. One machine has a terminal voltage of 270 V on no-load and 220V at a load current of 35 A, while the other has a voltage of 280V at no-load and 220 V at 50A. Calculate the output current of each machine and the bus bar voltage when the total load is 60A. What is the kW output of each machine under this condition? (16 marks )

2. A shunt generator has an induced e.m.f of 254V. When the generator is loaded, the terminal voltage is 240V. Neglecting armature reaction, find the load current if the armature resistance is 0.04ohm and field resistance is 24ohms.

3. Draw the diagram of a three-point starter and identify the various parts.

4. Two DC shunt generators are connected in parallel and supply a load to a DC shunt motor taking current of 150A. One generates an e.m.f of 250V and has an armature resistance of 0.2ohm and the other generates 255V and has an armature resistance of 0.3ohm. What are the motor output voltage and power output of each generator? (Neglect field current)

5. A 220V shunt motor takes 5A at No load. The armature resistance is 0.25ohm and field resistance is 200ohm. Calculate.

(i) Efficiency, when taking full load current of 50A.

(ii) Percentage change in speed between no-load to full-load.

Three-phase induction motors

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

What is slip for an induction motor? (4 marks)
If a 6- pole motor is supplied at 60Hz and runs with a slip of 5%, what is the actual rotor speed? or If a 4-pole motor is supplied at 60Hz and runs with a slip of 5%, what is the actual rotor speed?(4 marks)
Draw a simple ladder logic diagram of star-delta starting of an induction motor.

2. (a) Draw the circuit diagram and explain the working of the star/delta starter.

b) Explain with a diagram of how the direction of the single-phase induction motor is reversed.

3. Explain the construction and working of three-phase induction motor.

4. A 3-phase induction motor which is wound for 4-Poles, when running full load develops a useful torque of 100Nm; also the rotor e.m.f is observed to make 120-cycles/min. It is known that the torque lost on account of friction & core loss is 7Nm. Calculate the shaft power output, rotor copper loss, motor input, and motor efficiency.

5. Describe the step-by-step method of overhauling 10kW, 50Hz, 440V, 3-Phase Squirrel induction motor.

6. The shaft output of a 3-phase, 60Hz, induction motor is 80KW. The friction and windage losses are 920W, the stator core loss is 4300W and stator copper loss is 2690W. The rotor current and rotor resistance referred to stator are 110A and 0.15 respectively. If the slip is 3.8%, what is the percent efficiency?

7. A 400V, 4-pole, 50Hz, 3-phase, 10HP, star-connected induction motor has no load slip of 1% and full load slip of 4%. Find the following:

i) Synchronous speed ii) No-load speed iii) full-load speed iv) frequency of rotor current at full-load v) full load torque.

8. Write a short note on the principle of operation of induction motors. (4 marks)

a. Explain the phenomenon of crawling and cogging in a three-phase induction motor? (4 marks)

b. Difference between squirrel cage & wound rotor 3-phase induction motor

c. What is the condition to be satisfied for achieving maximum running torque in an induction motor?

d. The output of an induction motor running at 20% slip is 36.775kW and the friction and windage losses are 1500W. Find the rotor copper loss motor efficiency if stator losses are 3kW. (8 marks)

9. A 4-Pole, 3-phase, Induction motor operates from a supply whose frequency is 50Hz. Calculate.

i) The speed at which the magnetic field of the stator is rotating.

ii) Speed of the rotor, when the slip is 4%

iii) The frequency of the rotor when the slip is 3%

10. Describe the following starters:

(i) Three-point starter

(ii) Star-Delta starter

11. What is the soft starting of an induction motor? Describe with a circuit using thyristors used for soft starting. Discuss its advantages and disadvantages.

12. With reference to 3-phase induction motors:

a. Explain the phenomenon of crawling and cogging in these motors.

b. A 3-phase induction motor is wound for four poles and is supplied from a 50Hz system calculate:

i) The synchronous speed;

ii) The speed of the rotor when the slip is 4 percent;

iii) The rotor frequency when the speed of the rotor is 600r/min.

13. a) Difference between squirrel cage and wound rotor 3-phase induction motor.

b) The output of an induction motor running at 4% slip is 36.775kW and windage losses are 1500W. Find the rotor copper loss and motor efficiency if stator losses are 3kW. (8 marks).

Single-phase motor

1. With reference to single phase induction motor

(a) Using double field revolving field theory, explain why single phase induction motor is not self-starting.

(b) Draw a torque-speed characteristics of a single-phase induction motor on the basis of double field revolving field theory.

i) Split phase induction motor

ii) Capacitor motor

iii) Shaded pole motor

iv) Universal motor

Transformers

1. With reference to different types of transformers used onboard.

a. Discuss the basic principle of operation of a transformer (5marks)

b. Enumerate the different types of transformers used onboard also state their functions for which they are used (5 marks)

c. A 440/110V single phase transformer supplies a load of 5KW at 0.8 power factor load. Calculate the primary and secondary currents (Ignoring transformer power losses)? (6 marks)

d. A 440/220V single phase transformer supplies a load of 5kW at 0.8 power factor load. Calculate the primary and secondary currents (ignoring transformer power losses)? (6 marks)

2. In a container ship, a 3-phase delta/delta connected 6600/440 V, 60Hz transformer is feeding AMP supply from shore to 440 Volts switchboard. The transformer primary current takes a line current of 100AMP when secondary load p.f 0.8 lagging p.f is connected. Determine each coil- current and KW output of the transformer.

3. A 100KVA, 2400/240V, 50Hz, Single phase transformer has the no-load current of 0.64A and a core loss of 700W when its HV side is energized at rated voltage & frequency. Calculate the two components of no-load current. If this transformer supplies a load current of 40A at 0.8laging p.f. at its low voltage side, determine the primary current and its power factor. Ignore the leakage impedance drop.

4. What are the advantages of the transformer bank of three 1-phase transformers over a unit three-phase transformer of the same kVA rating?

a) What are the losses in the transformer? Mention the various factors which affect these losses.

b) In a 25kW, 3300/233V, 1-phase transformer the iron and full load copper losses are 350 watts and 400 watts respectively. Calculate the efficiency at half load, 0.8 p.f.

5. A 440V/110V, single-phase transformer takes a no-load current of 5A at power factor 0.25 lagging. On load, the transformer supplies 7.5kVA at p.f. 0.8 lagging. Calculate.

i) The transformer secondary current

ii) The transformer primary current and primary p.f.

6. A 3-phase the transformer has 900 turns in primary and 104 turns in secondary winding respectively. The primary winding is connected with the power supply of 66000V from HV switchboard. Calculate the secondary line voltage when the transformer is connected in

i) Star-delta connection ii) delta-Star connection

7. (a) Discuss the essential and desirable conditions to be fulfilled for operating two three-phase transformers in parallel.

(b) Two single phase transformers share a load of 400kVA at p.f. of 0.8 lagging. Their equivalent impedances referred to secondary winding are (1+2.5j) Ω and (1.5+3j) Ω respectively. Calculate the load shared by the transformers.

8. With reference to 3-phase Transformers:

a) Discuss the essential and desirable conditions to be fulfill for operating two three-phase transformers in parallel.

b) What are the advantages of transformer bank of three single- phase transformers over a unit three phase transformer of the same kVA rating.

c) In a 25KW, 3300/233V, 1-Phase transformer the iron and full load copper losses are 350 watts and 400 watts respectively. Calculate the efficiency at half load, 0.8 p.f.

9. With reference to 3-phase Transformers:

a) Describe the different types of losses occurring in power transformers

b) A single power transformer supplied a load of 20kVA at a p.f. of 0.81(lagging). The iron loss of the transformer is 200kW and the copper loss at this load is 180kW. Calculate

i) Efficiency

ii) if the load is now changed to 30kVA at a p.f. of 0.91(lagging), calculate new efficiency.

AC Machine (Three-phase synchronous Machines & AC Generators or Alternator)

1. Explain with the help of a neat diagram the operation of a brushless alternator. What would likely happen if one of the rotating Diodes fails and become:

(a) An open circuit?

(b) A short circuit? ( 16 marks )

2. An alternator does not build up any voltage after the start. Describe step by step procedure to solve the problem for all reasons.

a) Describe any two methods of determining the voltage regulation of a 3-phase alternator.

b) Two alternators are connected in parallel with what happens when we increase the excitation of one machine.

3. (i) What precaution must be taken when testing the insulation of generator cables and wiring connected to an AVR unit?

ii) How could you monitor the correct instant for synchronizing if the synchroscope and synchronizing lamps are not working?

iii) How the air-gap of an alternator is measured and why the air-gap of an alternator to be checked periodically.

4. With respect to (w.r.t.) paralleling of alternators:

a) If the synchroscope is malfunctioning, which instrument is the most essential to parallel an alternator with bulbar? Justify your answer.

b) Why it is desirable to operate paralleled alternators at the same power factor (p.f.).

c) Why it is necessary that incoming alternator frequency is more than busbar?

d) What are the likely consequences of attempting to close the incomer’s circuit breaker when the generator voltages are not in synchronism?

e) How could you monitor the correct instant for synchronizing without the aid of a synchroscope and synchronizing lamps?

5. The following loads are supplied by two alternators running in parallel:

i) 1400kW @ p.f. 0.86 lagging ii) 900kW @ p.f. 0.8 lagging

iii) 800kW @ p.f. unity IV) 500kW @ p.f. 0.8 leading

If the load on one machine is adjusted to 2100kW @ p.f. of 0.92. Find the load and power factor (p.f.) of the other machine.

6. With reference to diesel engine driven Alternators:

a. Explain the Automatic Voltage Regulator (AVR) to control the terminal voltage of the generator. (6 marks)

b. Two generators rated 2000kW and 4000kW operating in parallel. The droop settings of their governor are 4% and 5% respectively from no load to full load. Assuming that the generators are operating at 50Hz at no load, how would a load of 6000kW be will share between them? What will be the system frequency at this speed? Assuming free governor operation. (10 marks)

7. Two alternators running in parallel with Alternator-1 having 2000kW capacity with 4% speed drop and alternator-2 having 1000kW capacity with 4% speed drop. The no-load frequency is 62Hz. How much kW load shared by each alternator if the total load is 1200kW?

8. A total load of 8000kW at p.f. of 0.8 lagging is supplied by two alternators in parallel. One alternator supplies 6000kW at p.f. 0.9 lagging. Find the kVA rating of the other alternator and the p.f.

9. State the applications of the synchronous motors. Discuss how a synchronous motor can function as a synchronous capacitor. Compare synchronous motors with induction motor drives.

10. With respect to alternators onboard:

a. Briefly explain True Power, Apparent Power, and Power Factor?

b. The alternator is rated for 750kVA at 0.85 p.f. What is the maximum load (Kilowatt) that can be put on it? Would you be overloading the alternator if the Kilowatt reading were now 620kW and the power factor 0.80?

11. Sketch and describe the main engine shaft driven generator arrangement with an electronic system for frequency correction.

12. Explain the principle of operation of Synchronous Motor with a simple sketch. Where are synchronous motors used onboard?

13. Draw and explain the working of a Synchroscope. How could you monitor the correct instant for synchronizing without the aid of a synchroscope?

Power system (Including switchgear & Protection)

1. Explain three methods of overcurrent protection for electrical circuits. Explain with the aid of a diagram, the meaning of the inverse current time characteristic.

2. With respect to insulated and earthed neutral systems used onboard:

a) Discuss the advantages and disadvantages of both the insulated and earthed systems used onboard. (8 marks)

b) Discuss the consequences of earth fault in an earthed distribution system. (4 marks)

c) What would be the ohmic value of the NER to limit the earth fault to the full load rating of a 2 MW, 0.8pf, and 3.3KV 3Phase A.C generator? (4 marks)

d) What is earth fault and how do you identify earth fault in 440v system onboard? (4 marks)

3. With respect to Generators and Main circuit breakers and their protection devices:

What are safeties incorporated in Air Circuit Breaker (ACB) of ships generator and prime mover? (10 marks)

Write a short note on negative phase sequence relay (6 marks)

Explain the procedure to test reverse power relay?

4. (a) A 440 v 10 KW 0.8 PF 3 phase loaded supplied as shown. Calculate short circuit fault current at the load and at the main switchboard (8 marks)

b) What are the safety produce procedures if any work has to be carried out in leaves MSB bus-bar? (8 marks)

5. (a) What is the significance of earth fault in an isolated neutral system? Explain with a suitable diagram.

b) List the advantages and disadvantages of an electric propulsion system.

6. With respect to Circuit breakers compare the effectiveness of a current limiting circuit a breaker with that of an HRC fuse.

7. a) Explain briefly about checks and calibration of a thermostat which is used to stop an air compressor, when cooling water temperature goes to high?

b) What is the significance of earth fault in an isolated neutral system? Explain with a suitable diagram.

8. With respect to a three phase shipboard electrical distribution system:

a. Enumerate the advantages of an insulated neutral system.
b. Enumerate disadvantages of an insulated neutral system.
c. Describe how the Earth Neutral System is earthed.
d. Compare the use of an insulated neutral system as opposed to the use of an earthed neutral system with regard to the risk of electric shock from either system.

9. a) Discuss the criteria of the classification of marine high voltage for AC and DC system.

b) Sketch a ships HV distribution system and explain its features.

c) Discuss the various methods of testing the insulation of HV system. Mention the significance of PI Test; Why 3-terminals insulation testers are used in HV insulation measurements?

ELECTRICAL PROPULSION

1. Diesel-electric propulsion is now being chosen as the power plant for an increasingly wide variety of vessels.

a) Sketch a simple layout of such an installation

b) Explain the advantages of selecting such a plant.

2. List out the advantages and disadvantages of the electric propulsion system.

3. With reference to an emergency source of electrical power in cargo ships:-

a) Describe a typical power source

b) Give a typical list of essential services, which must be supplied simultaneously.

c) Explain how the emergency installation can be periodically tested.

Batteries, Electronics, Instrumentation & Control

1. (a) Draw and explain the block diagram of PLC?

(b) What are the equipment where the PLCs are used onboard?

2. (a) Explain why 3 wire RTD is perfect for accurate measurement of temperature? (8 marks)

(b) Explain with a diagram how the boiler water level is measured (8 marks)

3. (a) How to check and calibrate a thermostat which is used to stop an air compressor when the cooling tower goes to high.

(b) Describe an automatic control system capable of maintaining the jacket water temperature within close limits during wide changes in engine load; explain with a simple line sketch of a main engine cooling system.

4. (a) Explain with the aid of a diagram, a controller utilizing proportional plus integral action.

(b) Explain briefly what you know about “Pulse width Modulation” and how it can be applied for propulsion control.

5. (a) Describe the working of a single-phase full-wave rectifier with a resistive load. Draw the load voltage and current waveforms.

(b) Diode half-wave rectifier supply a resistive load of 100Ω from a 100V ac r.m.s voltage source. The diode is a resistance of 5Ω during the conduction state. Calculate

i) The DC output voltage ii) DC avg. load current

6. What is Zener diode and how does it regulate the voltage? What happens to the series current, load current, and Zener current when the dc input voltage of a Zener regulator increases? Draw a neat diagram of the Zener regulator and explain.

7. What is semiconductor devices? What are its advantages over thermionic devices? With respect to semiconductor devices describe the working principle and application of the following:

a. Zener diode

b. Transistor

c. Photocell

d. Thyristor

8. a) Explain the construction & principle of operation of permanent magnet moving coil (PMMC) type instrument.

b) A PMMC type the instrument has a coil of dimension 15mmX12mm. The flux density in the air gap is 1.8x10-3 Wb/m 2 and the spring constant is 0.4x10-6 Nm/rad. Determine the No. of turns required to produce an angular deflection of 90*when a current of 5mA is flowing through the coil.

9. (a) Explain the working of fuel oil leak off alarm system of Main Engine.

(b) Explain the operation of the Main Engine RRM Indication system.

10. (a) Draw & explain the basic flow and control diagram of the refrigeration system onboard ship.

(b) Write down the function of the following components:

(i) Thermo Couples (ii) DP Transmitter (iii) IP Converter (iv) IGBT

11. Briefly explain the Principle of Variable Frequency Drives (VFD). Discuss the advantages and disadvantages of VFDs onboard merchant vessels?

12. With reference to batteries onboard:

a) Distinguish between Lead-acid cell and Alkaline Cell

b) Describe how a battery of alkaline cells may be tested for its usefulness, after a long storage and if found deficient, how it can be remedied?

c) Explain how the ambient temperature is taken into account when determining the condition of the battery.

13. i) Sketch and describe hydraulic circuit of steering gear incorporating automatic isolation system.

ii) Explain emergency steering

ii) Describe the routine tests of steering gear as per SOLAS requirement.

14. a) By means of a schematic ckt. diagram illustrates the peak rectifier. If the supply voltage is v(t)= VmSinwt, what is the voltage across the load resistor?

b) A battery-charging ckt. As shown below fig. The forward resistance of the diode can be considered negligible and the reverse resistance infinite. The internal resistance of the battery is negligible. Calculate the necessary value of the variable resistance R so that the battery charging current is 1A.

Safeties

1. (a) Describe the routine tests required for self-contained breathing apparatus sets.

(b) Describe the procedure to be adopted to find missing personnel in a smoke-filled Accommodation area.

2. With Reference to entry into enclosed spaces

(a) Define enclosed space and give examples of enclosed spaces onboard. (4 marks)

(b) Describe hazards relating to entry into enclosed spaces on board

(d) Explain safety precaution is taken prior to entry into enclosed spaces onboard vessels. (8 marks)

3. With respect to the hazardous areas of tankers:

(i) Explain the term flameproof (Ext.) for electrical equipment.

(ii) State the type of electrical equipment that would be protected in this way.

(iii) List likely defects of flameproof equipment.

4. With reference to electrical safety onboard a vessel

(a) Write short note on “electric shock “(6 marks)

(b) Enumerate the relation between shock current levels, the applied voltage, and the body Resistance. (5marks)

5. How will you fight a fire in a purifier room? How will you at least restrict the fire if you are the first person to sight the fire in the purifier room?

6. How will you fight a fire in a galley? How will you at least restrict the fire if you are the first person to sight the fire in the galley?

7. With respect to MARPOL Annex-IV:

(a) Draw a biological sewage treatment plant and explain the principle of operation.

(b) Periodical maintenance and checks/tests required to be done to verify the effectiveness of the system.

8. With respect to MARPOL Annex-V

(a) Please explain the regulations stipulated for disposal of garbage under annex 5 MARPOL 73/78

(b) Please state the special area notified under Annex-V MARPOL73/78

9. With the aid of suitable line diagrams where ever required sketch and Describe a suitable Marine growth protection system (MGPS) installed on the vessel to prevent fouling of internal Sea Water system mention the important precautions if any while handling the system.t the minimum LSA to be carried out by passenger ship.

10. With reference to the fixed CO2 flooding system for firefighting on board ships, explain the following:

(a) Advantages and disadvantages of CO2as a fire fighting medium.

(b) The purpose of providing time delay with a suitable block and line diagram

11. (a) Describe CO2fixed firefighting system for machinery spaces and cargo spaces of the bulk carrier. or CO2 it to be released in engine room in case of fire. Briefly describe steps taken before it can be released.

b) Explain the safety precautions taken prior to the release of CO2to the engine room.

12. Which all matrix, checklists, and permits will you fill-up? Before commencing the work and who will authorize the work permits?

13. (a) You are working onboard the Deck Cargo crane. What are the hazards associated with working at height?

(b) What risk mitigation measures will you take to mitigate the hazards identified by you while working at heights?

(c) Which all risk assessment checklists, work checklist and work permits will you fill up before commencing the work and who will authorize the work permits?

14. (a) What are the safety incorporated in ACB of ship’s generator and Prime mover? (10 marks)

b) What are the safety produce procedures if any work have to be carried out in leaves MSB? Bus-bar (8marks)

15. (a) List the items which are contained in the training manual pertaining to life-saving appliances.

(b) Describe the frequency of abandon ship drills and fire drills and how they should be conducted.

(d) List the minimum LSA to be carried out by the passenger ship.

16. (a) Explain working of galley CO₂ firefighting control system

b) Explain working of electrical oven fitted in galley range with circuit diagram.

17. With reference to MARPOL Annex1:

a) Draw a 15ppm Oily water separator and Explain the Principle of operation.

b) Periodical maintenance & checks/tests required to be done to verify the effectiveness of the above system.

Numerical questions and answers

Please comments! We do take time and effort to answer these questions; if not, what is the point?