Marine Electrical engineering free professional question and answers you may come across during interview, examinations, and/or while working onboard ship.

Marine electrical engineering exam questions and answers:

As Marine electrical engineering below are questions which will guide you while prepare for job interviews and course exams. We will answer some of the questions, we want our audience to make a research and answer others via our comment box.

Electrical engineering basic Questions

1. Explain the principle of operation of the unified motor overload protection device?
2. Explain the principle of operation of the automatic power switching device UPP-1?
3. Explain the need for motor overload protection?
4. Explain how the motor is protected against overload by the traditional method. What are the disadvantages of such protection?
5. Explain the principles laid down in modern systems for protecting motors against overload?
6. Explain the concepts of motor protection against overload with direct temperature control.
7. Explain the principle of operation of the ship insulation resistance monitoring devices (electron).
8. Explain the principle of the organization of the operation of the ship insulation resistance monitoring devices?
9. Explain the operation of the light signaling device?
10. What is the need to protect the motors from unacceptable voltage reduction, how ?
11. Explain how electric motors are protected against unacceptable voltage reduction with a voltage relay. At what parameters of the contactors is this protection assigned to the voltage relay?
12. what are the principles laid down in modern systems for protecting electric motors against over-current
13. Explain how electric motors are protected against unacceptable voltage reduction by means of contactors. What parameters should a contactor have to be able to realize this protection??
14. Explain how protection against unacceptable reduction of electric motors of responsible consumers is implemented?
15. Explain how electric motors are protected from external short circuit, how are they organized?
16. Explain how generator overload protection is organized?
17. Explain how the protection of generators against reverse power is organized?
18. Explain how protection of generators against unacceptable voltage reduction is organized?
19. Explain how the current settings of the circuit breakers are organized when organizing selective protection.
20. Explain how the testing of circuit breakers is perform according to the maximum switching capacity.
21. Explain how is the (detuning) of the protection relay against unacceptable undervoltage reduction due to a short circuit?
22. Draw the protective characteristics of the installation machines and selective machines with a fixed time delay
23. Draw the protective characteristics of the generator machines with adjustable time delay.
24. Explain the principle of operation of the multivibrator of the light signaling device.
25. Explain the principle of operation of the magnetic amplifiers of the light signaling device and the device protecting the electric motor against overloads.

Answers to some of the above question:

Since we will like you to carry out more research regarding the above questions, lets start by giving you little summary answers.

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Talking about motor overload protection, contactors and relays are use to regulate the current flow/temperature. probably you might know the working principle of the simplest relay. incase you dont know, i will share that in few words

The simplest relay is activated by heat cause by high current flowing through the overload and over a bimetallic strip.  A bimetallic strip is a band of two different metals attach to each other where each metal has a different coefficient of thermal expansion.

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As this bimetallic strip heats up, one metal will expand faster than the other and cause the assembly to curve. When it gets hot enough the curvature will be enough for the contacts in the overload to become separated. Since the overload has a contact wired into the control circuit of the contactor, this effectively breaks the circuit and de-energizes the system. Once the bimetallic strip cools, it will straighten out and allow the circuit to close again.

Differents between Electrical Relay and contactor ?

When a relay is used to switch a large amount of electrical power through its contacts, it is designated by a special name: contactor. A contactor is typically control by a circuit which has a much lower power level than the switched circuit, such as a 24-volt coil electromagnet controlling a 230-volt motor switch

Contactors typically have multiple contacts, and those contacts are normally-open, so that power to the load is shut off when the coil is de-energized. Perhaps the most common industrial use for contactors is the control of electric motors.

Now over to you, lets hear from you, share answers on the comment box.

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