High Voltage System - Reason for having High Voltage System On board ships

As we already know about the voltages used onboard a ship. It is usually a 3phase, 60Hz, 440 Volts supply being generated and distributed onboard ship.

1. Higher power requirement on board ship is the foremost reason for the evolution of HV in ships.
2. Higher power requirement has been necessitated by development of larger vessel required for containers transport particularly reefers containers and cruise vessels.
3. Gas carriers needing extensive cargo cooling electric propulsion.
4. For a ship with large electrical power demand, it is necessary to utilize the benefits of a high voltage installation.

The design benefits relate to the simple ohms laws relationship that current (for a given power) is reduced as the voltage is increased. Working at high voltage onboard ship significantly reduces the relative overall size and weight of electrical power equipment.

When Heavy loads are connected to the Low voltage system the magnitude of current flow becomes too large resulting in overheating due to high iron and copper losses.

P = V * I * COS(Φ)

Copper losses = I^2 * R (KW)

Already High Voltage levels of 3.3 KV, 6.6 KV and 11 KV are regularly employed ashore for regional power distribution and industrial motor drives.

For example, a motor (let us assume a bow thruster), maybe a smaller size if it designed to operate on 6600 Volts. For the same power, the motor would be of a smaller size if is designed for 6600 Volts when compared to 440 Volts.

Thus these are the major reasons why recent ships have shifted towards the high voltage systems. The main disadvantage Highlighted by the owner, when working in an HV installation, is the very necessary adherence to stringent safety procedures.

Advantages:

1. For a given power, higher Voltage means Lower current, resulting in:
2. Reduction in size of generators, motors, cables, etc.
3. Saving of space and weight.
4. Ease of Installation.
5. Reduction in cost of Installation.
6. Lower losses- more efficient utilization of generated power.
7. Reduction in short circuit levels in the system which decides the design and application of the electrical equipment used in the power system.

Disadvantages:

1. Higher Insulation Requirements for cables and equipment used in the system.
2. Higher risk factor and the necessity for strictly adherence to stringent safety procedures.

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Electro Technical Officer(ETO) Exam Questions

Examination of Electrical Technical Officer

(Marine Electrotechnology and SSEP)

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

2. State the application of the synchronous motors. Discuss how a synchronous motor can function as a synchronous capacitor. Compare synchronous motors with induction motors drives?

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

4. With Reference to 3-phase transformers

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

b. What are the advantages of transformers bank of three 1-phase transformers over a unit three-phase transformers of the same KVA rating?

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

6. With respect to alternator onboard:

a. Briefly explain true power, Apparent power, and power factor?

b. The alternator is rated for 750 KVA at 0.85 PF, what is the maximum load (KW) that can be put on it? Would you be overloading the alternator if the KW reading were now 620 KW and the PF 0.80?

7. Write a short note on “electric shock”?

8. 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?

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Electromagnetic Theory Multiple Choice Questions

Electronics and communication Multiple Choice Questions

1. The electric field intensity magnitude at a point (1,2,3) m, in Cartesian coordinates due to a charge(1/9) nC located at the origin is equal

a. 3.3 V/m

b. 0.33 V/m

c. 0.033 V/m

d. zero

2. The divergence theorem applies to?

a. static fields only

b. time-varying fields only

c. both static as well as time-varying fields

d. magnetic fields only

3. For a plane electromagnetic wave traveling in a linear, isotropic, homogeneous stationary medium?

a. E and H lie in the same plane

b. E * H = 0

c. E and H are mutually perpendicular

d. None of these

4. An electromagnetic wave propagates from a dielectric medium to the interface with free space. If the angle incidence is the critical angle of 30 degrees, the relative permittivity of the dielectric medium is?

a. 8

b. 4.5

c. 6.8

d. 4

5. When an electromagnetic wave traveling in one medium strike upon a second medium having a different conductivity the wave will be?

a. neither transmitted and partially reflected

b. totally reflected

c. partially transmitted and partially reflected

d. totally transmitted

6. In the perfect conductor, the incident and the reflected waves combine to produce?

a. linearly polarized

b. circularly polarized

c. elliptically polarized

d. horizontal polarized

7. The polarization of dielectric materials results in?

a. absorption of electrons

b. the release of high-velocity protons

c. creation of electric dipoles

d. production of eddy currents

8. The absorption of radio waves by the atmosphere depends on?

a. the polarization of atmosphere

b. the polarization of the waves

c. their frequency

d. their distance from the emitter

9. As an electromagnetic wave travels in free space the only one of the following can happen to them?

a. reflection

b. absorption

c. attenuation

d. refraction

10. When a current carrying conductor is brought into the magnetic field the force that moves the conductor depends upon which of the following?

a. The value of current

b. The weight of conductor

c. The direction of the conductor

d.  None of these

Answers:

1.  b

2. c

3. c

4. d

5. c

6. c

7. c

8. c

9. c

10. a

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Different type of Controllers Onboard

1.  Small-scale controller

-These type of controller are mostly of microcontroller type or of based on other active elements like OP-AMP based.

-They are deployed to control and monitor very small task in a system.eg:- oxygen analyzer, pH monitoring, and alarm system.

-Specifically, these type of system give out the Digital alarms but with one more OP-AMP integrated into the system it gives out the analog signals.

-configuring and changing the signal to these devices is very difficult with limited instruments available onboard.

-make sure connection and solder point are not getting loosen due to vibrations.

-Ensure proper shock absorber/cushion is maintained.

-Ensure earthing point is not loosed.

-Ensure Potentiometer setting are not changed due to vibration.

2.   PID Controllers(-ve feedback closed loop controller)

-They are process controllers designed to monitor the analog signals and controls the actuators via analog or digital signals onboard they are used for temperature, flow, level.

They come in standard industrial grade hard plastic package of fix number of screw connecting pins.

-These controllers can be reconfigured but caution must be taken with the parameters. If not done as per process then it can cause damage to the machine as well as to the operator.

      

-Parameters of the PID comes in its operation manual.

This controller can be connected in many configurations as master-slave, +ve feedforward, -ve feed forward system. Not much repairing can be done onboard on PID, they can only be reconfigured and these controllers don't decalibrate on there own.

-Before reconfiguration ensure good input and the output signal from PID because changing parameters mostly takes the expertise level and knowledge.

-Insufficient power.

-I/O terminals damage.

-The controller might be in manual/maintainance mode 

3.    PLC Controllers

These are programmable controllers for digital and analog actuation of actuators. They provide an open architecture and flexibility again PLC comes in size and variety, once they are programmed then only wiring and instrumentaion work resides.

Types of PLC Onboard

a. MICRO PLC-(programmable relays)

-These are programmable relays with less number of I/O terminals with onboard programming facility on them.

eg:-

Schneider electric Zelio

seimens LOGO

b. Compact PLC

-They are relevant to medium scale automation with the limited number of IO terminals, but can be added with I/O modules upto 10 in Nos. They have 2 or 3 communication ports

c. Modular PLC

-These are very varsatile PLC controller for high scale automation with I/O terminals in range of thousands. 

-There I/O module comes in standard addon block with easy installation and 2 or more inbuilt communication ports.

-PLC comes in many brands(Allen Bradely, schneider electric, siemens, ABB, mitshubishi, delta automation, Omron and many more) with their different software  of different version

-Although many of us know the PLC ladder programming but never try to program the PLC onboard as it will void the manufacturer or programmers warranty.

-PLC indications give out the health of it, still, problems in PLC is very limited

   -battery drained or damaged

   -unregulated power supply

   -PLC in error/fault mode due to memory or hardware reason.  

4.    DCS(Distributed Controller system)

-These are very powerful controllers with many controllers connected to it which are distributed throughout the system.

-It has its own SCADA integrated to it which can control and aquize the data on different systems and communicate to one redundant server.

-DCS is a tailor made automation syatem for a specific process. Nowdays many brands started to manufacture DCS.

In marine sector, it is used on fully automated ships like of NYK.

-They are very reduant and expensive controll system that is placed on board, nowadays company started to interface neural logic along with PLC and HLL language.

eg:-

honeywell dcs system 

yokogawa dcs system

ABB DCS system

Now a days companys like siemens are trying to make DCS more compact with the there PCS7 system and more is on the way.

-These controllers no matter which type or brand they work very efficiently without failing.

-There is very less probability of Controller Damage but a very high probability of input failure due to a faulty sensor or faulty input line.Still, in case of any replacement, make sure connection are connected in the same way as they were previously.

ABOUT THE AUTHOR

JOGINDER SINGH is an Automation Engineer and currently working in GE Shipping as an Electro Techno Officer.

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Electro Technical Officer(ETO) Exam Questions and Answers

Selective Questions and answers for Electro technical officer - ETO. Multiple choice Questions and answer for ETO COC (Certificate for Competency) exam.

1. According to NAND logic gate has ______.

a. High input and a high output

b. Low input and a low output

c. Low input and a high output

d. None of the above

2. What is the use of silicon controlled rectifier (SCR) is a solid-state device used to change ____?

a. AC to DC and control relatively high load current

b. AC to DC and control relatively low load current

c. DC to AC and control relatively low load current

d. DC to AC and control relatively high load current

3. What is the function of transducer's is to _____?

a. Convert one form of energy to another

b. Prevent current flow

c. Transmit electrical energy

d. Produce mechanical energy

4. A varistor is known as _______?

a. A voltage-dependent diode

b. A current-dependent diode

c. A voltage-dependent resistor

d. A current-dependent resistor

5. A memory device that loses its contents when power is lost is ____?

a. Non Volatile

b. Static

c. Volatile

d. Random

6. The function of the varistor incorporated in the excitation system of the alternator is to 

a. Reduce the winding temperature

b. Stabilize voltage

c. Take care of spikes

d. None of the above

7. Which of the following circuits would require the least amount of filtering?

a. A full wave rectifier

b. A rectifier

c. A half wave rectifier

d. A bridge rectifier

8. What is the reason of  Surge voltage originates in power systems due to _______?

a. Switching operations

b. Lighting

c.Fault

d. Any of the above

9. After isolation, LOTO procedures are performed, which electrical device requires any stored electrical energy to be discharged before any work may safely begin?

a. Capaciotr

b. Choke coil

c. Potential transfomer

d. Resistor bank

Answer:

1. Low input and a high output

2. AC to DC and control relatively high load current

3. Convert one form of energy to another

4. A voltage-dependent resistor

5. Volatile

6. Take care of spikes

7. A bridge rectifier

8. Any of the above

9. Capacitor

Share your answers in the comments box, for authentic rule and regulation of shipping Industry visit DG Shipping website. #cocexam #eto

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Electro Technical Officer(ETO) Exam Questions and Answers

Selective Questions and answers for Electro technical officer - ETO. Multiple choice Questions and answer for ETO COC (Certificate for Competency) exam.

1. The seven segment arrangement for a numerical display on consoles, test meters, and other applications can be either ______ ?

a. A BCD or an OCD

b. An LED or an LCD 

c. A UJT or a BJT

d. A JFET or an LCD

2. When checking a good SCR or TRIAC with an ohmmeter it will ____.

a. Display a low resistance with positive on the anode, -ve probe on the cathode and a high resistance when it is reversed

b. Display a low resistance in both directions

c. Display a high resistance in both directions

d.  Display a high resistance with -ve on the anode, +ve probe on the cathode and a low resistance when it is reversed

3. A microprocessor unit, a memory unit, and an input unit form a/ an _____?

a. Complier

b. ALU

c. CPU

d. Microcomputer

4. Which of these sets of logic gates are designated as universal gates?

a. XOR, NOR NAND

b. NOR, NAND, XNOR

c. NOR, NAND

d. OR, NOT, AND

5. When a step input is given to an op-amp integrator, the output will be ____?

a. A sinusoidal wave

b. A triangular wave with DC bias

c. A ramp

d. A rectangular wave 

6. When transistors are used in digital circuits they usually operate in the _____?

a. Breakdown Region

b. Linear region

c. Active region

d. Saturation and cut off regions

7. What minimum energy level will ignite gases falling in group II c?

a. 69 micro J

b. 400 micro J

c. 280  micro J

d. 29 micro J

Answer:

1. An LED or an LCD

2. Display a high resistance in both directions

3. Microcomputer

4. NOR, NAND

5. A ramp

6. Saturation and cut off regions

7. 29 micro J

Share your answers in the comments box, for authentic rule and regulation of shipping Industry visit DG Shipping website. #cocexam #eto

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Top Best Ways To Stay Healthy and Fit On Board Ship

As said "Health is wealth" and seafarers face challenges on daily basis. So it's important to understand how to stay healthy and fit onboard ship.

1. POSITIVE STATE OF MIND:- 

a) Stay Connected with your loved ones whenever in Network.

b) Find your inner bliss by doing what makes you happy. Like hobbies, playing indoor games etc.

c) Be adaptable. Keep an open mind to change and welcome innovations.

d) While working in a team, be open to ideas.

2. DOING EXERCISE ON DAILY BASIS (AT LEAST 30 – 60 MINS):-

a) Doing regular exercise makes the body pump blood more efficiently.

b) Boosts your mood.

c) Increases stamina in the long run. 

d) Enhances the immune system. 

e) Use GYMNASIUM AVAILABLE On Board.

f) Get ENGAGED In Some Sports: some vessels have extra spaces that can be used for outdoor sports. It is also a good way to bond with your colleagues.

“On ships where you have to deal with the same faces every day. Just try to put a smile on your face and the world will unknowingly smile back at you. On ships where you have to deal with the same faces every day.”

3. EARLY MORNING / EVENING JOG:-

a) An early morning or evening brisk walk or jog for 30-40 minutes around the ship in good weather can create wonders. 

b) You will enjoy both the benefits of the fresh ocean breeze for your lungs and can walk to a healthier you.

4. DRINKING MORE WATER (at least 8 GLASSES) ON DAILY BASIS:-

a) Helps in body detoxification.

b) Improves concentration.

c) Gives you energy

d) Good for your heart and blood

e) Strengthens your immune system.

5. HEALTHY  MEAL:-

a) Reduce intake of Sweets as Desert. (prefer Dark Chocolate over if the craving for) And Switch to healthy and Juicy Fruits.

b) Vegetables.

c) Meat- Choose white meat over red meat.

d) Boiled Eggs- Only Egg white and no yolk.

e) Choose Brown Breads over white bread.

f) Never miss Breakfast: Choose Oats meals for Breakfast.

ABOUT THE AUTHOR

Shubham Shivaji Kamble is an Electro Technical Officer at GE shipping. An Electrical engineer by profession, who has worked as an Executive engineer at Oberoi Hotels and resort.

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Electro Technical Officer(ETO) Exam Questions and Answers

Questions and answers for Electro technical officer - ETO. Multiple choice Questions and answer for ETO COC (Certificate for Competency) exam.

1. What happens when a low voltage protection circuit is used in an electric motor's starter to ______ ?

a. Trip the contactor when the motor develops a short circuit due to low voltage

b. Prevent the motor from restarting automatically in case it stops

c. Trip the main contactor when the motor over speeds due to low voltage

d. Allow the motor to restart automatically on the restoration of voltage without manual resetting.

2. What do mean by discoloration of the rotor bars in a squirrel-cage motor is typical evidence of _____ ?

a. Overheating

b. Vibration

c. Moistured

d. All of the above

3. What is the functional name of an electrical device which prevents simultaneous energizing of loads thereby prventing damage or injury?

a. Electrical interlock device

b. Monitoring device

c. Mechanical limit device

d. All of above

4. If a digital multimeter is set up in the resistance mode to test a capacitor, what would the display read if the capacitor is discharged?

a. The ohmic value would initially read very low, but over time the ohmic value would gradually rise to an extremely high value.

b. The ohmic value would read very high.

c. The ohmic value would read very low.

d. The ohmic value would initially very high, but over time it drops to a low value.

5. When an ohmmeter is used to test a semiconductor diode, you find a low resistance in both the forward and reverse bias direction, this indicates that the diode has a/an ____ ?

a. Short

b. Good capacitive quality

c. Open

d. Good resistive quality

6. Which of the listed conditions is an advantage of a PN diode over a vacuum tube?

a. No warm-up time

b. More robust

c. Longer life

d. All of above

7. When troubleshooting most electronic circuits, the loading effects can be minimized by using a voltameter with a/ an _____ ?

a. I/P impedance that is much less than the impedance of the circuit in the voltage is being measured.

b. The sensitivity of more than 1000 V/ohm

c.  I/P impedance that is much greater than the impedance of the circuit in the voltage is being measured.

d. The sensitivity of less than 1000 V/ohm

8. In a Transistor, _______

a. The emitter, Collector, and Base are the basic elements

b. Emitter separates base and Collector

c. PNP and PNP are one the same basic typed

d. Collector separates Base and Emitter

9. An SCR is a solid state device used for what functional purpose?

a. To function like a switching device and control relatively low load current

b. To function as an amplifier and control relatively high load current

c. To function like a switching device and control relatively high load current

d. To function as an amplifier and control relatively low load current

10. Which of the following statement represents an application of an SCR?

a. It is used to sense the flame in an automated burner.

b. It is used to provide DC power for the main propulsion motor.

c. It is used as a voltage reference diode.

d. It is used to eliminate power supply.

Answers:

1. Prevent the motor from restarting automatically in case it stops

2. Overheating

3. Electrical interlock device

4. The ohmic value would initially read very low, but over time the ohmic value would gradually rise to an extremely high value.

5. Short

6. All of above

7. I/P impedance that is much greater than the impedance of the circuit in the voltage is being measured.

8. The emitter, Collector, and Base are the basic elements

9. To function like a switching device and control relatively high load current

10. It is used to provide DC power for the main propulsion motor.

Share your answers in the comments box, for authentic rule and regulation of shipping Industry visit DG Shipping website. #cocexam #eto

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