Elstan’s Marine Electrical Technology Guide

Spreading knowledge for a better life at sea with safer ships and cleaner oceans






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Chapter 1 - Overview of a Ship’s Electrical System

1)         A block diagram shows______.

2)         A circuit diagram shows ______.

3)         A system diagram shows _______. 

4)         A wiring diagram shows _______.

5)         The abbreviation ‘MCC’ stands for______. 

6)         By calculating the kW and kilovar demand the ______ can be calculated. 

7)         Load analysis obtains information from the ______.

8)         The emergency generator must be situated ______.

9)         The maximum voltages for lighting is _______. 

10)     The maximum voltage for generators and permanently connected power equipment is _______ volts. 

11)     The maximum voltage for very large installations is ________. 

12)     A cargo ship’s generators are typically rated from _______ to _______ kW. 

13)     A ship’s electrical equipment should be capable of operating when the vessel is _______ and at any angle of list (static) up to and including _______ either way. 

14)     A ship’s electrical equipment should be capable of operating when the vessel is _______ and at any angle of roll up to and including _______ either way. 

15)     A ship’s emergency generators can be rated from _______ to _______ kW. 

16)     Load analysis helps to calculate ________.

17)     The demand factor is the ratio of _________ to consumption. 

18)     As per SOLAS Regulations, at least _______ generators _______ of which must be independent of the propeller shaft r.p.m.

19)     Machines should be installed with their axis of rotation either _______ or ________. 

20)     The IEC definition of low a.c. voltage is any voltage between _______ and _______.

21)     List the various supplies commonly available onboard a ship.

22)     What do you understand by Load Analysis?

23)     How should electrical equipment be installed on board a ship? What are the adverse effects of not positioning them correctly?

24)     List the various diagrams that depict the working of electrical equipment?

25)     Write short notes on each type of electrical diagram.

26)     With the help of a figure explain the general layout and functions of various electrical equipment onboard a ship.

27)     What are the effects of inclination on marine electrical equipment?

28)     Briefly explain the conditions that could prevail at sea and how they relate to the operation of electrical equipment on board a ship.

29)     What are the effects of temperature on electrical equipment onboard a ship?

30)     What are the primary essential services onboard a ship?

31)     What are the secondary essential services onboard a ship?

32)     How would you differentiate between generation and distribution?

33)     State the significance of the emergency services.

34)     Why do generators form the heart of the electrical system onboard a ship?

35)     Briefly explain what you understand by a power management system.

36)     State the highest voltages approved for use in a marine electrical system.

37)     How should the axis of rotation be while installing rotating machines onboard a ship? What are the adverse effects of not positioning them adequately?

Chapter 2 – Electrical Safety

1)         Ex stands for _______.

2)         Ex i(a) means _______.

3)         Ex i(b) means _______.

4)         Equipment in the Flameproof category is classified as ________.

5)         Equipment in the Increased Safety category is classified as ________.

6)         Equipment in the Pressurised category is classified as ________.

7)         Equipment in the Non-incendive category is classified as ________.

8)         Equipment in the Intrinsically Safe category is classified as ________.

9)         Only equipment with Ex i(a) standard (and Ex s that is specially certified) equipment are permitted for use in ________ areas.

10)     To indicate the probability of an explosive gas-air mixture being present in hazardous areas they are classified into zones as ________.

11)     Only equipment with Ex (i) a or b; Ex d; Ex e; Ex m, Ex p, or Ex s protection are allowed in ________ areas.

12)     If a motor is to be installed in a flammable (hazardous) area the Ex rating should be __.

13)     An example of Zone 0 on a tanker is _______.

14)     _________ areas are hazardous only under abnormal conditions and are usually freely ventilated and all safe-type of equipment are permitted to operate provided they conform to the stipulated requirement.

15)     Explosive gas-air mixture continuously present or present for long periods ________. Explosive gas-air mixture likely to occur during normal operation ________.

16)     Explosive gas-air mixture is not likely to occur and any occurrence would generally be for a short time in ________ areas.

17)     In terms of electric current, there is a sensation that shock is occurring when the value is about________ mA / A / kA.

18)     The upper limit of safe or harmless range of electric current is ________ mA / A / kA.

19)     In terms of electric current at the let-go threshold, the victim cannot shake loose from the source of shock and perspires; this is approximately at ________ mA / A / kA.

20)     There is sustained muscle contraction and cramping when the value of electric (shock) current is ________.

21)     There is extreme pain, physical exhaustion, fainting, irreversible nerve damage; possibility of ventricular fibrillation (heart); respiratory arrest with possible asphyxiation when the value of electric (shock) current is ________.

22)     There is ventricular fibrillation (heart) and death if the current in excess of _________ mA / A / kA passes through the body trunk.

23)     There is fibrillation, amnesia (memory loss), burns, and severe electrolysis at contact sites when the value of electric (shock) current is ________.

24)     There is little likelihood of survival when the value of electric (shock) current is _____.

25)     Typical dry full contact body resistance is about _______ Ω / / M Ω.

26)     Zone, 0 Zone 1 and Zone 2 mean ______ , ______ and ______ respectively.

27)     The recognised standard frequencies onboard ships are _______ and _______ Hz. 

28)     A shock current as low as ______ mA / A / kA can be fatal.

29)     In terms of shock current, d.c. is _______ effective as compared to a.c.

30)     BASEEFA stands for_______.

31)     IEC stands for _______.

32)     The typical body resistance can fall to about ________ at 250 V.

33)     Risk assessment is carried out to ________.

34)     Fumes released by volatile solvents are ________.

35)     To differentiate the types of tankers, their cargoes are tested for ________.

36)     As per BS and IEC standards, the high voltages are defined as ____ a.c. and ____d.c.

37)     At what location the sign “Men at work” should be placed while working on electrical equipment?

38)     What is the significance of earthing of electrical equipment?

39)     What is generally the Ex protection for an electric motor?

40)     What precaution is to be taken to ensure that the electrical equipment is not switched on while working?

41)     What must be done to ascertain complete isolation of supply in Electrical installations?

42)     What is to be checked to confirm safe working practice is followed in ship?

43)     While working within the scavenging manifold in the main engine, the hand lamp should be rated at ________.

44)     What is the minimum amount of electric current that can cause death to a human being?

45)     What is the factor that can increase the risk of shock in case there is an earth fault in the electrical installation?

46)     What is the minimum safe insulation in an electrical Installation?

47)     What factor can increase the potential risk when working in a battery room?

48)     When work is to be carried out on an electrical installation, what extra precautions must be taken to prevent against an electric shock after isolation of the power supply?

49)     What precautions must be taken for portable electrical hand tools in order to avoid a lethal shock as its hand gripping area is large? 

50)     What is the safe voltage (in the case of a dry human body condition) to prevent an electric shock?

51)     What precaution must be taken to prevent against an explosion while changing lamps in the pump room lighting in a tanker?

52)     What would be the consequences if work on the electrical installation commences without taking Safety precautions?

53)     What is the optimum location for earthing a welding machine in order to avoid circulation current?

54)     What is the voltage applicable for welding in a ship?

55)     Does current flow through the hull during welding? If so, why don't you get a shock?

56)     Describe the precautions before commencing work on electrical equipment.

57)     What safety are precautions associated with the operation of a HV (High Voltage) system?

58)     What are the fundamental requirements for the safe installation of electrical equipment onboard a ship?

59)     What is the maximum voltage regarded as reasonably safe for portable power tools? Justify your answer.

60)     State the maximum safe current a human body can tolerate.

61)     What is the maximum shock voltage to earth for a centre-tapped 110V tool transformer?

62)     What are the two types of Electric shock? What is the first thing that must be done when finding a victim of electric shock? Give two methods of how this is done.

63)     State the first aid to be administered to a person exposed to electric shock

64)     Why are high voltage systems more dangerous than low/medium systems?

65)     List the various type of Explosion Proof Equipment and explain each type in one or two lines.

66)     What do you understand about the Do’s and Don’ts of Electrical safety? Explain.

67)     While ensuring Electrical Safety, certain Active and Passive measures are adopted. List them and briefly explain each measure.

68)     Identify the hazardous areas on a ship and with the help of a table / chart determine what type of equipment should be installed in each location.

69)     Demonstrate safe methods to test and use portable electrical tools.

70)     State the type pulley belt specified for use in hazardous zones.

71)     Why is special lighting used in battery rooms?

72)     Describe the precautions for storing, replacing and repairing electronic PCBs.

73)     With the help of simple sketches explain the basic design features of Ex d equipment.

74)     State the essential features of switches certified for use in hazardous zones.

75)     Using suitable diagrams, explain the role of Zener barrier devices in Ex i equipment.

76)     State the essential features of fittings for illumination in hazardous zones.

77)     In your own words explain safe installations for tankers.

78)     Differentiate the tankers by the cargo they carry?

79)     State the importance of proper ventilation when using volatile electro-cleaners, varnishes and paints having solvents.

80)     Describe the hazardous zones, classification of type, classification pertinent to different class of vessels and constructional and operational details.

81)     With reference to electrical equipment in areas aboard ship having potentially flammable atmospheres:

a)          Explain the hazards involved.

b)          State the design features that render the equipment safe.

c)          Explain the precautions necessary when maintenance work is being carried out.

82)       Briefly explain the hazards of ESD and how it can be mitigated.

Chapter 3 - AC Distribution Systems

1)         Single-phase power is only used for ________ distances.

2)         Feeders are the ______which connect the _______to the distributors to an allotted area.

3)         The recognized standard frequencies onboard ships are ______ and _______Hz.

4)         The most common power frequency adopted for use on board ships is ______.

5)         What is the general concept of AC power distribution?

6)         List the common voltages and frequencies onboard ships. List the purpose of each voltage level.

7)         Why is AC distribution preferred over DC distribution onboard a ship?

8)         Why is 60 Hz a preferred frequency over 50 Hz on board a ship?

9)         What are the differences between feeders and distributors?

10)     What do you understand by a primary distribution system?

11)     What do you understand by a secondary distribution system?

12)     What is a bus bar distribution system? Explain the same with a simple diagram.

13)     What is a cross-linked distribution system? Explain its significance with a simple diagram.

14)     What is a Primary Power Bus?

15)     What is a radial distribution system? Explain the same with a suitable diagram.

16)     With a suitable diagram explain the single-phase two-wire system.

17)     With a suitable diagram explain single-phase three-wire system.

18)     Enumerate the difference between three-phase three-wire and three-phase four-wire systems.

19)     With a suitable diagram, explain the three-phase three-wire method of distribution.

20)     With a suitable diagram, explain the three-phase four-wire method of distribution.

21)     With simple diagrams explain the various distribution systems onboard ships.

22)     What is the significance of a feeder circuit breaker?

23)     With the help of a diagram, explain the layout of electrical equipment on a modern cargo ship.

24)     What are the main features of a high-voltage electrical system onboard a LNG vessel?

25)     What do you understand by automatic power and frequency control?

Chapter 4 - Emergency Power And Shore Supply

1)         The steering system is a load that is too heavy to be connected to the emergency generator (True / False)

2)         As per SOLAS Regulations, the emergency generator must be situated ________

3)         Emergency diesel engines must operate satisfactorily up to a ____O list and ____ O trim. 

4)         A diesel driven emergency generator is prevented from being paralleled with the ship's service generators with the help of ________.

5)         Special interlocks in the control circuits of the circuit breakers at each end of the inter-connector between MSB and ESB to _________.

6)         The _______ sections of an emergency switchboard are used to supply power for alarm signals under emergency conditions.

7)         A shore power supply breaker should be closed only when _________. 

8)         The instruments available on the shore connection box are _______

9)         Under normal circumstances, the emergency switchboard is kept alive (True / False).

10)     What are the basic requirements for an emergency power system onboard a ship?

11)     Why is the emergency generator operated with fuel at a flash point of ³ 43°C?

12)     With the help of a flow chart, explain the Manual / Automatic Starting Procedure for Emergency Generators.

13)     With a neat diagram explain the method of supplying emergency power onboard a ship.

14)     In a few sentences list the Emergency Power Supply requirements for Passenger and Cargo vessels.

15)     Why must an emergency electrical power system be proved?

16)     When must an emergency power source come on line?

17)     List the sequence of operations when overcoming a blackout situation onboard

18)     Why are both an emergency generator and batteries recommended?

19)     How long must battery powered lighting run on passenger ships?

20)     When is the testing of emergency power supplies done?

21)     What are the special interlocks fitted to the main and emergency generation circuit breakers for?

22)     State the sequence of auto-starting of an emergency generator.

23)     What are two methods of auto-starting an emergency generator?

24)     How is the emergency generator’s auto-start circuit tested?

25)     What is the only way to test the performance of the emergency power supply?

26)     After a black out the emergency generator comes on. On restoring the main supply we close the circuit breaker of the main generator without bothering about synchronizing. How is this possible?

27)     When does a ship require shore supply and what is the basic procedure to obtain it?

28)     List the critical equipment supplied with power from the emergency generator

29)     Demonstrate the method of carrying out routine tests on emergency generator

30)     Describe the indications provided for shore power

31)     Outline the interlock arrangement between MSB (Main Switch Board) and ESB (Emergency Switch Board) and testing methods

32)     Explain the precautionary measures upon change-over to shore supply

33)     State the method of testing the 24V D.C. power supply to navigation, communication and engine room control console in event of power failure from the main supply.

34)     What are the basic indicators available on the Emergency Switch Board?

Chapter 5 - Isolated and Earthed Neutral Systems

1)         Marine electrical equipment is normally tested to _______ volts. 

2)         The earth-fault indicator on the main switchboard is activated. The best procedure for locating the grounded circuit is to ________. 

3)         If all of the ground detection lamps burn with equal brilliance, whether the test button is depressed or   released, then ________.

4)         In a three-phase electrical system, three earth-fault lamps are provided. One lamp goes dark and the others glow brightly when the test button is pressed. When the push button is released, all lamps glow with equal brilliance. You should conclude that ________.

5)         On a tanker, as per SOLAS Regulations the neutral point of a medium voltage alternator should be ________ the earth.

6)         The main purpose of using a high voltage system on board ship is to ________

7)         What is the meaning of earthing in a ship?

8)         What consideration is used to choose the value of an earthing resistor?

9)         Describe the neutral earthing system in a main power distribution system

10)     Describe the isolated neutral and earthed neutral systems in 3 phase distribution and significance of each

11)     What is the difference between the neutral and earth?

12)     What is the role of a NER in High-voltage System Earthing?

13)     What is the maximum voltage of electrical systems in a tanker?

14)     What is the significance of earth faults in an earthed neutral system? Explain with a suitable diagram.

15)     What is the purpose of the earth fault indication on the switch board?

16)     What happens with one earth fault in an earthed distribution system?

17)     Which distribution system is more efficient in maintaining supply?

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

19)     What role does an earth-fault indicator play onboard? Explain any type with a suitable diagram.

20)     With a suitable diagram explain the method of locating and eliminating an earth-fault in a simple distribution system.

21)     Why must an earth return path have low impedance?

22)     With the help of a simple circuit, explain how lamps are used to detect an earth fault?

23)     What indications does an earth fault instrument give? How does it work?

24)     With suitable diagrams differentiate between an isolated and earthed neutral system

25)     How can earth faults affect an Earthed Neutral System?

26)     How can earth faults affect an Isolated Neutral System?

27)     How is an earth-fault detected and overcome?

28)     List the causes of earth faults and briefly explain each cause. How can they be prevented?

29)     With the help of a diagram explain how an earth-fault alarm works

30)     What are the simple maintenance procedures to be carried out in order to prevent an earth fault?

31)     If you get an earth fault alarm, what will you do?

32)     Explain the procedure for identifying low insulation on lighting circuits.

Chapter 6 – Alternators

1)         The maximum field voltage for an average alternator on board a ship is about ________mV / V / kV.

2)         One factor that determines the frequency of an alternator is the _________.

3)         In an alternator, direct current from a separate source is passed through the windings of the rotor with the help of __________.

4)         The cycles per second developed by the alternator is governed by __________.

5)         Two of the factors governing the frequency of an operating alternator are the ________ and ________.

6)         The voltage induced in the windings of an alternator depends mainly on __________.

7)         Loss of or weak residual magnetism in an alternator or generator can be corrected for by__________.

8)         In a 60 Hz system, the frequency is permitted between________.

9)         The range of speeds of a shaft generator is generally________ to ________ r.p.m.

10)     The AVR of the Shaft generator can accept ________% of variation of main engine speed.

11)     The static frequency converter for a shaft generator can satisfactorily function within _________ % of the main engine's rated speed.

12)     The permissible air gap in a shaft generator may be________ mm / cm / m.

13)     The power factor of an alternator is determined by the ________.

14)     The rotating diodes of a polyphase exciter in a brushless alternator are situated on / at ________.

15)     The prime mover’s speed defines the frequency of the output; it is governed by the formula ________.

16)     A synchronous compensator is used along with a shaft generator for _________.

17)     With a neat diagram explain Fleming's Right Hand Rule and its role in the operation of a generator.

18)     What is alternating current?

19)      How are voltage and frequency achieved?

20)     What is the basic principle on which an alternator functions? Explain with a suitable diagram.

21)     Is the ship's alternator Star wound or Delta wound and why?

22)     Why are a.c. generators constructed with a stationary armature and revolving fields?

23)     What is the relationship between speed, frequency and poles?

24)     List the factors that will determine the output frequency.

25)     Differentiate between a cylindrical and a salient pole rotor.

26)     Draw and explain a conventional shaft-generator system.

27)     Explain the circuit for an exhaust-gas turbo-generator system.

28)     What are harmonics and what are the adverse effects on current waveforms?

29)     With a suitable diagram explain the role of a static frequency converter in a shaft generator system.

30)     With a suitable diagram explain the role of a synchronous compensator in a shaft generator system.

31)     What is a synchronous condenser? Where and why is it used?

32)     With the help of a neat flow chart, explain the method of bringing a generator onto a dead bus bar.

33)     Explain the Thyristor operation and reactor (A.C, D.C.) for the frequency converter

34)     How is a high-voltage shaft generator different from other shaft generators?

35)     Is the rotating field or stationary field alternator more advantageous? Justify your answer with suitable diagrams.

36)     With the help of a diagram, explain the High-voltage System for a Dredger.

37)     How is it possible to run an alternator with the help of a shaft-driven DC generator?

38)     With a neat diagram explain a shaft generator system using a DC drive and tachogenerator to maintain constant output.          

39)     Write short notes on the various components of a basic alternator. Supplement them with diagrams where necessary.

40)     What is the meaning of residual magnetism?

41)     State reasons for residual magnetism loss and symptoms of such problem.

42)     Is the field current in an alternator AC or DC?

43)     What is a brushless alternator?

44)     In terms of excitation, how is a brushless alternator different from other alternators?  Explain with suitable sketches.

45)     What is likely to happen if one of the rotating diodes of a brushless generator’s excitation system fails?

46)     List the type of bearings, system of lubrication, and electrical isolation in generator.

47)     Describe the “Pedestal” insulation arrangement of large alternators and a.c. machines on board.

48)     What is the significance of shaft generators? How are they classified?

49)     Even though the main engine runs at varying speeds, how does the alternator maintain constant frequency? How does an inverter play a role?

50)     State the synchronous condensers operation for power factor correction.

51)     What are synchronous condensers and why are they needed?

52)     With simple sketches explain the different ways in which generators can be coupled to main engines.

53)     Describe auto start sequence on recovering power to MSB (Main Switch Board) and its purpose.

54)     If you press the ACB Close button on an idle generator what will happen?

55)     What is the main reason for power factor reduction onboard a ship? How important is this to the ship’s electrical system?

56)     Briefly explain harmonics and its effects.

57)     Describe the purpose of a space heater.

58)     Describe methods of cooling.

59)     List the safety monitoring devices provided with water cooled generator

60)     What is the effect of failure of water-cooling on the operation of large generator?

61)     What are the consequences of not insulating the shaft bearings of large generators?

62)     How is the flow of shaft current prevented in large generators?

Chapter 7 - Direct Current Machines

1)         Explain the operation of a basic d.c. generator?

2)         What are the methods adopted to reduce armature reaction?

3)         List the types of direct current generators.

4)         With simple sketches explain the series wound generator.

5)         What is a shunt wound generator? Explain the same with suitable sketches. 

6)         Briefly explain a compound wound generator.

7)         Why is flashing required? How is it done?

8)         Compare series and shunt fields in a few sentences.

9)         List the types of direct current motors.

10)     With simple sketches explain the series wound motor.

11)     What is a shunt wound motor? Explain the same with suitable sketches. 

12)     How is the speed of a DC motor varied?

13)     How is the direction of a DC motor varied?

14)     Briefly explain a compound wound generator.

15)     What are over-, flat-, and under-compounding?

16)     What is critical field resistance?

17)     How is a direct current generator controlled?

18)     How can you take a generator on load?

19)     Explain parallel operation of d.c. generators.

20)     What is a diverter and how does it work?

21)     With the help of a suitable diagram, explain the significance of dynamic braking.

22)     What is the significance of the Field poles in a DC generator? Compare the same with the Field of a DC motor.

23)     What is the role of the Armature in a DC generator?  Compare it with an armature of a DC motor.

24)     Why is a commutator needed in a DC machine? With a suitable diagram explain its function.

25)     With suitable sketches explain armature reaction. 

26)     Why are compensating windings needed in a DC machine? Where are they located?

27)     What would happen if commutating poles or interpoles are not used in a DC generator?

Chapter 8 – Automatic Voltage Regulators

1)         Automatic voltage regulators provided on switchboards function to _________.

2)         The output voltage of a 440 volt, 60 Hz, 4-pole, 1500 r.p.m. alternator is controlled by the _________.

3)         The AVR is capable of maintaining a steady output when the alternator's output varies between ________.

4)         The output voltage from the main alternator must be within ________ in 1.5 seconds.

5)         The output voltage from the emergency alternator must be within ______ in 5 seconds.

6)         When large DOL squirrel cage motors are started, the power factor may fall to______.

7)         An AVR helps to maintain the output Voltage within ________ %.

8)         The input to the AVR is taken from the _________.

9)         The output of the AVR is connected to _________.

10)     The AVR is meant to control _________.

11)     A static excitation system is capable of recovery (to the steady-state value) within ____ second(s).

12)     The instantaneous reduction in voltage of an alternator, resulting from an increase in load, and prior to the AVR correcting the situation, is called ____________.

13)     What is the meaning of excitation in an alternator? How is it supplied?

14)     Draw and explain the transformer-based static excitation system.

15)     Briefly describe the operation of an automatic voltage regulator.

16)     Explain the significance of the pick-up point of the generator’s output and the routing of the control circuit’s input in an AVR.

17)     How does a thyristor-controlled static AVR work? Explain the same with a suitable diagram.

18)     With a suitable graph explain what you know about alternator response for different excitation systems.

19)     What are the effects of kW loading?

20)     What are the effects of kVAr loading?

21)     Explain Alternator Response in relation to different types of AVRs.

22)     Explain the 3-phase transformer-based static excitation system.

23)     Explain why the setting of an automatic voltage regulator for an a.c. generator should not be altered while the machine is operating in parallel with another machine.

24)     State the various safety devices on an Automatic Voltage Regulator, explaining the conditions under which they operate.

25)     How does a Zener diode work?

26)     Explain the basic role of a Zener diode in an AVR.

27)     How does a thyristor work?

28)     Explain the role of a thyristor in an AVR.

29)     Explain the operation of an automatic voltage regulator of the Zener bridge type.

30)     What are the effects of kW loading?

31)     What are the effects of kVAr loading?

32)     What is the significance of UFRO in a modern AVR?

33)     Where is an excitation trip used? What is the symptom of incorrect setting?

34)     Explain over voltage protection in about 5 lines.

35)     Write short notes on Dip and Dwell.

36)     What is the role of the ramp potentiometer?

37)     Why is droop important?

38)     What are the droop settings to ensure kVAr load sharing?

39)     What is the role of the over-voltage de-excitation breaker?

40)     What is the significance of over voltage protection in a generator’s system?

Chapter 9 – Panel Instrumentation

1)         Errors exist in all measuring systems and arise from the difference between the indicated and _______ values. 

2)         AC Power P = ________.

3)         The voltage rating of a wattmeter is generally limited to ________V.

4)         A 3-phase wattmeter consists of _________ moving coils.

5)         With a balanced load, even one single-phase wattmeter may be used to measure 3-phase power (T / F).

6)         The reactive power Q = ________.

7)         An electrodynamometer can be used as a wattmeter and power factor meter (T / F).

8)         A moving iron meter can be used as a wattmeter and power factor meter (T / F).

9)         An electrodynamometer cannot be used for frequency measurement (T / F).

10)     The vibrating reed frequency meter works on the principle of ________.

11)     In a Weston-type Synchroscope, the lamp goes dark when the two voltages are _______.

12)     The phase sequence indicator is a vital instrument for shore supply (T / F).

13)     A handheld digital (optical) tachometer could give an erroneous reading if ________.

14)     Identify the component provided to measure load current and the operational principle

15)     How does an electric tachometer monitor an engine’s speed?

16)     What is root mean square value?

17)     Modern handheld digital tachometers operate by counting light pulses returned to the unit by _________.

18)     Generally voltmeters in alternating current circuits are calibrated to indicate the ____.

19)     A switchboard ammeter indicates a reading slightly above "zero" when the leads are disconnected, this is caused by ___________.

20)     When troubleshooting most electronic circuits, "loading effect" can be minimized by using a voltmeter with a / an ________.

21)     With a suitable sketch explain the Electrodynamometer Frequency Meter.

22)     Explain the operation of an Electrodynamometer Wattmeter. 

23)     How is 3-phase power consumption measured using two wattmeters for either star or delta connected loads?  Write down the relevant equations also.

24)     With the help of a neat diagram explain one method by which frequency is measured.

25)     What is the meaning of power factor?

26)     What is the benefit of improving power factor?

27)     What is KVA?

28)     How are line and phase voltages related?

29)     What is the meaning of saying I and V are in phase?

30)     What is the difference between KW, KVA and KVAR? Explain the operation of a electrodynamometer-based single-phase Power Factor Meter.

31)     Explain the operation of a electrodynamometer-based three-phase Power Factor Meter.

32)     Describe the method of reading a power factor meter with reference to four segments.

33)     How is 3 phase-power consumption measured using one wattmeter?

34)     Where does reactive power go?

35)     How does a single-phase Varmeter work?

36)     How is reactive-power consumption measured using a two element wattmeter?

37)     With the help of a neat diagram explain the Mechanical Resonance type Frequency Meter.

38)     With the help of a neat diagram explain the operation of a Weston type Synchroscope.

39)     With a suitable sketch explain the Rotating-type Phase Sequence Indicator.

40)     With a suitable sketch explain the Static-type Phase Sequence Indicator.

41)     How does an AC Electric Tachometer work? Explain it with a suitable diagram?

42)     How does a DC Electric Tachometer work? Explain it with a suitable diagram?

Chapter 10 - Paralleling of Alternators

1)         The governor control switch of an alternator is moved to the “raise” position; this will cause_______.

2)         An alternator that is being paralleled with another that is on load; the moment the circuit breaker is closed, the frequency of the incoming alternator will normally _____.

3)         While synchronising two alternators, the incoming machine must always be ________.

4)         When using the 3-lamp method for synchronising, the top lamp must be dark while the bottom two must glow with the same brilliancy. Justify this statement.

5)         A voltmeter may be used to parallel two alternators (T / F).

6)         In case a synchroscope is faulty, paralleling of two alternators is impossible (T / F)

7)         The purpose of the reverse power relay, provided on a ship's service alternator panel, is to trip the circuit in case the _________.

8)         The division of the reactive KVA between paralleled alternators is initiated by ______.

9)         KW load sharing between paralleled generators can be changed by ________.

10)     As load is increased for an alternator, the prime mover eventually slows down resulting in _________.

11)     An alternator panel is fitted with both synchronising lamps and a synchroscope. When the synchroscope pointer reaches the 12 O'clock position, the two bottom lamps are bright and the top one is dark. This means __________.

12)     When paralleling two alternators, the synchroscope selector switch should be set so as to monitor the frequency of the __________ alternator.

13)     When paralleling two alternators, the frequency of the incoming generator, just prior to closing the circuit breaker, should be __________.

14)     When two alternators are being paralleled, the breaker should be closed with the synchroscope pointer rotating in the __________direction.

15)     While attempting to parallel two alternators if the synchroscope pointer stops at a position other than 0 and the circuit breaker is closed at this moment then __________. 

16)     An alternator operating in parallel loses its excitation. This will cause _________.

17)     After paralleling two alternators the next step is to balance the __________.

18)     An alternator operating in parallel begins to vibrate severely and eventually trips with the help of the reverse power relay. This is due to_________.

19)     If field excitation is suddenly lost to an alternator operating in parallel, that alternator will __________.

20)     If the energy input is significantly reduced to the prime mover of one alternator operating in parallel with others, that alternator will _________.

21)     If two alternators have just been paralleled, the kW load is initially distributed by   ___________.

22)     You are attempting to parallel two alternators and the synchroscope pointer is revolving slowly in the “fast” direction. You should ___________.

23)     The kilowatt load sharing between two alternators that are operating in parallel is controlled by the settings and characteristics of the __________.

24)     To stop an alternator operating in parallel with another, you must first of all _________.

25)     When paralleled, alternators must have the same _________.

26)     Motoring of an alternator is undesirable because __________. 

27)     The frequency of an alternator is adjusted by means of the _________.

28)     When paralleling two alternators using three synchronizing lamps, the flickering of all three lamps becomes progressively slower and slower. This means the __________.

29)     Voltage failure of an alternator may be caused by ____________.

30)     The output voltage of a 440 volt, 60 hertz alternator is controlled by the _________.

31)     If the pointer of the synchroscope is rotating in the slow direction when you are preparing to parallel two alternators, the __________.

32)     A change in field excitation of an alternator operating in parallel will cause a change in its __________.

33)     A constant output voltage from an alternator is maintained by the __________.

34)     Before the generator is paralleled with the MSB, if its governor setting is increased then _________.

35)     The division of kilowatt load between two paralleled alternators is determined by the __________.

36)     An overall balance of load sharing for kW and kVAR can be seen by comparing ___________

37)     The ideal time for synchronising of generators is when ________

38)     Generators No.1 and 2 are operating in parallel and prime mover of generator No.2 suffers a total fuel loss - the consequence is:

39)     Why is it necessary that incoming alternator frequency is more than bus bar?

40)     Why do we close the breaker at 12 O'clock and not at 6 O'clock?

41)     Why is it desirable to operate paralleled alternators at the same power factor?

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

43)     Draw a simple sketch to depict the instrumentation on a Synchronising Panel. 

44)     When voltages are equal in frequency where does the synchroscope pointer lie? Why is this so?

45)     What is the maximum time a synchroscope should be online for?                    

46)     Write short notes on auto synchronising

47)     Explain the method to test the “Auto Cut In” of the stand by generator

48)     Write short notes on manual synchronising

49)     Write short notes on the importance of synchronising lamps.

50)     Explain paralleling of alternators using a synchroscope.

51)     Explain the alternate method to parallel alternators, if the synchroscope is faulty

52)     With the help of a phasor diagram explain Excitation Control while paralleling alternators.

53)     What are the phases in paralleling of alternators? With relevant diagrams explain either the synchroscope or three-lamp method.

54)     How could you monitor the correct instant for synchronising without the aid of a synchroscope or synchronising lamps?

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

56)     With a neat Flow Chart, explain Manual and Automatic Synchronising.

57)     What should be done after successful synchronisation?

58)     What is load sharing? With the help of relevant diagrams explain load sharing between two alternators. What is the effect of frequency on load bearing of an alternator?

59)     Explain kW and kVAr load sharing with a suitable graph.

60)     Explain methods to ensure that load sharing between generators is satisfactory

61)     What is used to adjust the power factor?

62)     What happens when there is a loss of excitation in a parallel alternator system? Which alternator would trip and why?

63)     What do you understand by Paralleling?

64)     Describe the load sharing process of generators and state its purpose

65)     List the factors that will determine the output frequency with two generators running in parallel

66)     With the help of a phasor diagram explain Throttle Control while paralleling alternators

67)     Differentiate between throttle control and excitation control while paralleling alternators.

68)     Explain droop characteristics while paralleling.

69)     Write short notes on negative droop.

70)     If an alternator has isochronous characteristics, how will you parallel this machine with another? Justify your action.

Chapter 11 - Switchboards and Switchgear

1)      The MCB trip mechanism is based on the ________ principle.

2)      Apart from the main contacts in an ACB, there are _____ contacts too. 

3)      Busbars are generally made of _________________.

4)      MCBs generally operate with a range up to_____________.

5)      RCCBs are also known as ______.

6)      The abbreviation RCBO stands for________.

7)      The main panels / sections of a main switch board are________.

8)      _______ mA RCCBs are recommended for life safety while _________ are for fire protection.

9)      MCCBs generally operate with a I range from _________up to __________.

10)   Instead of fuses, ________ breakers are commonly used in final distribution boards.

11)   ______ breaker has the least breaking capacity.

12)   Protection against sustained overloads occurring in a MCCB is ensured by _________.

13)   The arc resulting from the tripping of a circuit breaker is prevented from damaging the contacts because of _________.

14)   A moulded-case circuit breaker protects equipment against short circuits by using a / an ________.

15)   The operation of the high voltage bow thruster motor is controlled by _________.

16)   What is the duty of a switchboard?

17)   List the main differences between an a.c. and a d.c. switchboard.

18)   Describe the controls provided on MSB (Main Switch Board) for synchronization.

19)   Explain the functions of the main components of an air circuit breaker.               

20)   With a simple sketch explain the functions of instrumentation on a Synchronising Panel.

21)   What are repulsive conductors? Which device uses this? Explain the same with the help of a sketch.

22)   Protection against sustained overloads occurring in moulded-case circuit breakers is provided by a / an_________.

a)      over voltage release

b)      thermal acting trip

c)      thermal overload relay

d)      current overload relay

23)   Where a thermal-acting breaker is required to be used in an area of unusually high, low, or constantly fluctuating temperatures, an ambient compensating element must be used. This element consists of a ______________.

a)      cylindrical spring on the contact arm     b)            second bimetal element

c)      conical spring on the contact arm           d)            second electromagnet

24)   The copper flexible plays an important role in a breaker. Explain the same in not more than three lines.

25)   Explain the role of arcing contacts and the arc chute in an ACB.

26)   Why is a vacuum circuit breaker preferred for HV applications?

27)   What are the properties of vacuum and SF6 gas breakers widely used in high voltage systems?

28)   What are the principal factors to be considered when selecting a circuit breaker?

29)   What factors determine the current rating of a circuit breaker?

30)   By what percentage would the rating of a circuit breaker change from its free air value due to switchboard mounting?

31)   What is the primary function of a circuit breaker?

32)   What are the four fault ratings of a circuit breaker?

33)   What would happen if the circuit breaker was rated at less than the expected fault level?

34)   What is the full form of ACB?

35)   What are the salient features of an ACB?

36)   With a simple sketch explain the layout of a Main Switchboard.

37)   With a simple sketch explain the operation of an Air Circuit Breaker.

38)   State why, a breaker may not open upon severe and prolonged voltage dip.

39)   What current rating (range) is used with MCCBs?

40)   What is the main difference between a relay and a contactor?

41)   With a simple sketch explain the role of a busbar.

42)   What maintenance can be carried out on a MCB?

43)   What is skin effect?

44)   In few lines explain the effect of harmonics at receptacle load centres.

45)   With a simple sketch explain the functions of instrumentation on a Generator Panel.                           

46)   At what value of earth currents are earth leakage breakers set?

47)   How will a moulded-case circuit breaker react after it has tripped, as a result of an overloaded circuit? 

48)   Describe the actions to be taken in the instance of fire in the main generator panel.

Chapter 12 - Starters for Alternating Current Motors

1)         A DOL starter is normally used in a / an ________ type of motor.

2)         An induction motor is expected to draw the highest starting current with a _____ starter.

3)         Auto transformer starters are often used for motors above ________ kW.

4)         The high starting current in a motor normally drops to normal at about ______% of its speed.

5)         Autotransformer starters are used with polyphase induction motors to _______.

6)         A soft starter can be connected in ________ with the motor.

7)         Modern soft start controllers use ________ devices.

8)         The main part of a motor starter includes ________.

9)         A solenoid works on the ________ principle.

10)     The Function of a Star-Delta starter of a motor is to ________.

11)     A 3-phase induction motor needs frequent starting and operation in forward and reverse directions; a ________ type of starter will be preferred.

12)     What is a magnetic contactor? Where is it used?

13)     Name the types of starters used in marine applications.

14)     With the help of simple sketches explain the most common types of starters used and why?

15)     What is the significance of starting torque? What is the approximate value while starting a motor with a DOL starter?

16)     Why is the contactor the heart of every motor starter? Explain this with a suitable sketch.

17)     Sketch a simple diagram of a direct on line starter, showing in detail the overload and single phase protection trip.

18)     Sketch a direct on line starter suitable for a three phase a.c. induction motor.

19)     Explain the limitations of the direct on line starter with respect to length of starting time and repeated successive starts.

20)     What is the starting current of an induction motor as compared to the full load current?

21)     Describe the function of thermal overload relay on motors.

22)     A slip ring induction motor is considered to be a high torque induction motor. Why is this so?

23)     What is the meaning of Star winding/ Delta winding?

24)     How does a basic star-delta circuit work? 

25)     List the areas where timers find applications in motor starters.

26)     Draw and explain circuit of a star-delta starter for a main seawater pump.

27)     With the help of a neat diagram explain the operation of a D.O.L. Starter - with automatic level control.

28)     What is the basic circuit behind an engine room crane? Explain its operation with a suitable sketch.

29)     When connected in star what is the voltage as a percentage of full load voltage?

30)     Why are back-up fuses needed for a motor starter?

31)     What is the most common reduced voltage starter?

32)     What are the voltage tappings within an autotransformer? Why are they used?

33)     With autotransformer starters what is used to overcome the transition switching problem?

34)     What is the significance of an auxiliary relay in an autotransformer starter’s circuit?

35)     How is a low voltage situation taken care of in a starter?

36)     Draw and explain the power and control circuits of a starter for a slip-ring induction motor.

37)     How is a starter for a slip-ring induction motor superior to a D.O.L. starter?

38)     With the help of a neat diagram explain the operation of a basic Auto-transformer Starter.

39)     Draw and explain the power and control circuits of an Auto-transformer Starter.

40)     Explain the operation of a soft starter and its advantages.

41)     Write short notes on:

a)       Open Loop Soft Starter

b)       Closed Loop Soft Starter

42)     How are soft starters rated? Give suitable examples to prove your point.

43)     How is the speed control of induction motors achieved?

44)     What are the motors employed for different operations of overhead cranes?

45)     State the basic precautionary measure to protect the generator when switching large capacity machinery connected to the Emergency Switch Board.

Chapter 13 - Fault Protection Devices

1)         Describe the protective devices peculiar to A.C. switchboards.

2)         Under fault conditions what should be the last protection device to operate?

3)         Why is plain overload protection insufficient in the case of a large alternator?

4)         Instantaneous short circuit trips normally operate within ________ sec(s).

5)         Motor fuses are typically rated at ________ times the full load current.

6)         Overload trip relays generally function in about  ________ second(s).

7)         Thermistor-based protection circuits are normally related to _________.

8)         HRC means _________ and is related to a ________.

9)         IDMT relay is the abbreviation for _________ and is used for ________ protection.

10)     The current rating of an overload trip is between _______% & ________ % above the maximum rating.

11)     Preference trips generally operate with time delays of _______, ________ & _______ respectively.

12)     The purpose of a main switchboard circuit breaker's reverse-power trip is to __________.

13)     How does the IDMT Relay work? Explain with a simple diagram.

14)     The current at which a magnetic-type overload relay tends to trip may be decreased by raising the plunger further into the magnetic circuit of the relay. This action____.

a)       reduces magnetic pull on the plunger and requires more current to trip the relay.

b)       reduces magnetic pull on the plunger and requires less current to trip the relay.

c)       increases magnetic pull on the plunger and requires more current to trip the relay.

d)       increases magnetic pull on the plunger and requires less current to trip the relay.

15)     Fuses placed in series with a thermal trip-type circuit breaker are used for __________.

16)     Differential protection of a generator ensures protection against _______.

17)     A circuit breaker and a fuse have a basic similarity in that they both________.

a)       Can be reset to energize the circuit.

b)       Should open the circuit when overloaded, will burn out when an over current flow develops.

18)     Under-voltage trips are frequently installed on switchboard circuit breakers to trip when __________.

19)     An Alternator circuit breaker is protected by _______.

20)     The current rating of an overload trip is rated between _______.

21)     In case of overload, the motor is protected by _______.

22)     Protective devices used for any electrical faults on distribution boards are _______.

23)     The main objective of a preferential tripping arrangement is to _______.

24)     To maintain the preference relay trip settings as originally specified they must be periodically tested by _______.

25)     A 3-phase induction motor is running on balanced supply; suddenly a fuse in one of the phases rupture and the motor continues to operate. This is known as _______.

26)     The function of a thermal overload relay in the case of a motor starter is _______.

27)     A 3-phase delta-connected induction motor continues to run under single-phasing conditions. It is likely to result in _______.

28)     Determine the types of protection devices for DC switchgear and their operation.

29)     What is the meaning of “Overload”? What is the normal setting of overload relays?

30)     State the location, type and operation of a generator circuit breaker OCR (Over Current Relay).

31)     What is a short circuit and how can short-circuit faults develop in a generator and its external circuit?

32)     What is the usual result of a short circuit? How may the occurrence of such a fault be minimized?

33)     What determines the value of the short circuit fault current?

34)     In few sentences and a basic diagram, explain thermistor-based protection.

35)     Where is under-voltage protection used? How does the mechanism function?  

36)     How does the instantaneous short circuit relay function? Explain with a diagram.

37)     State why preferential tripping in a marine electrical distribution system is required.

38)     With the aid of a sketch, describe a typical arrangement to provide three stages of tripping and an instantaneous protection against short circuit.

39)     What do you understand by protection discrimination? 

40)     At what value of voltage drop does the undervoltage trip operate?

41)     Why are motor starters fitted with undervoltage trips?

42)     What kinds of relays are used for undervoltage protection?

43)     With a diagram, briefly explain overload protection in a.c. circuits.

44)     With a diagram, briefly explain overload protection in d.c. circuits.

45)     What course of action needs to be taken when a generator is overloaded?

46)     What apart from overload can initiate preference tripping? Explain this with a suitable flow chart.

47)     How is preference tripping tested?

48)     In alternators above 5000 kVA what is required in the machine windings?

49)     What is surge? Write short notes on surges in d.c. and a.c. circuits.

50)     Why is a steam turbine overspeed trip connected to the circuit breaker trip circuit?

51)     What kind of overcurrent protection is found in MCCB and MCBs?

52)     Describe the protective devices provided on distribution boards against faults and overloads.

53)     Describe the function of thermal overload relay on motors.

54)     How is the overcurrent protection tested?

55)     Why is higher viscosity fluid used in marine dashpots?

56)     How does an electronic overcurrent relay operate?

57)     How is a generator circuit breaker’s OCR (Over Current Relay) set and tested?

58)     What is the common characteristic of all overcurrent relays?

59)     What is the most common form of overload protection? 

60)     A 3-phase short circuit occurs on the main busbars and the short circuit trip of the running generator breaker fails to operate. Explain how the under voltage relay provides a back up.

61)     What is the advantage of a thermal relay over a magnetic relay?