Most Important Electrical Engineer Interview Question and answer

Most Important Electrical Engineer Interview Question and answer

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Prepare By Eng. Syed Muhammad Afreen Ali (MSc . BSc - Engineering)

1.What are the three most common types of cable for transmitting power?

• An understanding of voltage capacities

• An understanding of cable sizes

• An understanding of the voltage volumes that differentiate high from low

• Multiple versus solitary power sources

• Systems with one versus multiple cables

• The effects of multiple cable systems on voltage

2. Could you explain about reverse power relay?

Example: "Cable types are typically categorized by either size or capacity. With respect to capacity, there are three types: low, high and super tension cables. Cable that carries less than 1,000 volts is low tension; between 1,000 and 23,000 volts is high tension; and anything between 66 kV to 132 kV is super tension."

3.What type of cables are used for transmissions?

Types of Data Transmission Cables

·         Twisted-Pair Cable. A twisted pair cable consists of two copper conductors, each one with its own plastic insulation and twisted together. ...

·         Coaxial Cable. Coaxial cable (coax) carries high frequency signals than twisted-pair cables. ...

·         Fiber-Optic Cable. A fiber optic cable transmits signals in the form of light.

 Why is AC systems preferred to DC systems?

Due to following reasons, AC systems are preferred over DC systems: a. It is easy to maintain and change the voltage of AC electricity for transmission and distribution. ... Primarily, for distribution/transmission reasons - It has lower losses because it can be stepped up and down easily

4. What is the difference between generator and alternator?

An alternator can be called a type of generator. ... Both alternators and generators convert mechanical energy into electrical energy. The main difference between them is in regard to what spins and what is fixed. In an alternator, electricity is produced when a magnetic field spins inside the stator (windings of wire).

5. What is the basic loading condition Transformer?

Transformer Voltage Regulation. The voltage regulation of a transformer is defined as the change in secondary terminal voltage when the transformer loading is at its maximum, i.e. full-load applied while the primary supply voltage is held constant.

6. What are the possible causes for low power factor?

Causes of low Power Factor. The main cause of low Power factor is Inductive Load. As in pure inductive circuit, Current lags 90° from Voltage, this large difference of phase angle between current and voltage causes zero power factor

6. Why motor are rated as KW while transformer rated in kVA?

Copper losses ( I²R)depends on Current which passing through transformerwinding while Iron Losses or Core Losses or Insulation Losses depends on Voltage. So the Cu Losses depend on the rating current of the load so the load type will determine the powerfactor P.F ,Thats why the rating of Transformer in kVA,Not inkW.

7. Say there is air conditioner of 1Ton, what does that mean?:

1 Ton AC covers 80 to 120 sq.ft area. The 144 sq ft is on border range. If you have many windows or if your room sun facing then buying 1.5 Ton AC is good choice.

8. If I have a 25kVA generator, how many 1.5 Ton Air conditioner can be used?

EER(Energy Efficiency Ratio)=cooling capacity of ac/power consumed by ac. cooling capacity of 1 ton is equal to 3.517 kW of power. AC consists of two units, Indoor unit which is called the evaporator and the Outdoor Unit which called the Compressor.

9. You would be aware that transformer has an insulating oil, which oil is that?

Transformer oil or insulating oil is an oil that is stable at high temperatures and has excellent electrical insulating properties. It is used in oil-filled transformers, some types of high-voltage capacitors, fluorescent lamp ballasts, and some types of high-voltage switches and circuit breakers.

10. You may have noticed there are fuse and circuit breakers. What is the difference between the both?

A fuse is a small, thin conductor designed to melt and separate into two pieces for the purpose of breaking acircuit in the event of excessive current. A circuit breaker is a specially designed switch that automatically opens to interrupt circuit current in the event of an overcurrent condition.

11.Can you explain Norton's Theorem in a single sentence?

Example: "One power source and one resistor is equal of multiple power sources and resistors on a linear circuit."

12.What is an induction motor?

Basic working principle of an Induction Motor. In a DC motor, supply is needed to be given for the stator winding as well as the rotor winding. But in aninduction motor only the stator winding is fed with an AC supply. Alternating flux is produced around the stator winding due to AC supply.

13.What is difference between fuse and relay?

So to sum up, a fuse is a one time protection device that interrupts a circuit. A relayis a device controlled by another part of the circuit and operated to connect or interrupt the circuit many times. ... Relay switches current flow on and off when energized/de energized.

14.What are the advantages of fuse?

Advantages of an Electrical Fuse. It is the cheapest form of protection, and it does need any maintenance. Its operation is completely automatic and requires less time as compared to circuit breakers. The smaller sizes of fuse element impose a current limiting effect under short-circuit conditions.

15.What is the difference between relay and switch?

Switches are manually actuated by the user. Relays are controlled by energizing an electro magnet, which in turn causes the contacts to open/close. Usually, at least in the US, the relay is said to “make” (close) or “break” (open). In eaaence, a rely is aswitch, controlled by another device.

16.What is the difference between relay and contactor?

Contactors and Relays perform the same task of switching a circuit. ... Both are electromagnetic switches and operate under similar principles. The differencecomes if we see from the application perspective. Contactors are used for high voltage switching purposes whereas relays are used for low voltage switching.

17.How does an electrical relay work?

A relay is an electromagnetic switch operated by a relatively small electric current that can turn on or off a much larger electric current. The heart of a relay is an electromagnet (a coil of wire that becomes a temporary magnet when electricity flows through it).

18.What is the difference between circuit breaker and isolator?

Difference between Isolator and Circuit Breaker: Isolator is an off-load device while, circuit breaker is an on-load device. Isolator is a switch operated manually, which separate the circuit from the power main and discharges the trapped chargesin the circuit. ... ISOLATOR is a Mechanical device which acts as a switch.

19. What is the use of overload relay?

Thermal overload relays are economic electromechanical protection devices for the main circuit. They offer reliable protection for motors in the event of overload or phase failure. The thermal overload relay can make up a compact starting solution together with contactors.

20. What is protective relay in power system?

In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker when a fault is detected. ... Important transmission lines and generators have cubicles dedicated to protection, with many individual electromechanical devices, or one or two microprocessor relays.

21.What is MHO relay?

A mho Relay is a high-speed relay and is also known as the admittance relay. In this relay operating torque is obtained by the volt-amperes element and the controlling element is developed due to the voltage element. It means a mho relayis a voltage controlled directional relay.

22.What is Translay relay?

TRANSLAY SCHEME FOR FEEDER PROTECTION. This system is similar to voltage balance system except that here balance or opposition is between the voltages induced in the secondary windings wound on the relay magnet and not between the secondary voltages of the line current transformers

23.What is backup protection?

When remote backup is used to provide backup protection for a single ProtectionSystem failure or a failure of a circuit breaker to interrupt current, the relays at the remote station are set sensitive enough that they can detect all faults that should be cleared from the adjacent (local) substation for which backup

24. What is primary protection?

The main protection or primary protection is the first line protection which provides quick-acting and selective clearing of a fault within the boundary of the circuit section or element it protects. The main protection is provided in each section of an electrical installation.

25. What is zone of protection?

“Zones of protection” is one strategy that can be used to provide the level of security demanded today. Protective relay engineers keep utility grids and equipment safe from faults and system unbalances by dividing the grid into zones, each with a unique protection scheme. Overlapping zones provide backupprotection.

Project experience

• Describe your favorite project you’ve worked on.
• What was your role?
• Describe a technical problem you encountered and how you solved it.
• What quality controls did you employ?
• What did you do best while working on this project?
• What could you improve on?
• What did you learn from this project?
• What design tools are you familiar with?
• What is your favorite part of the project lifecycle?
• Do you have any technical writing experience?
• What has been your greatest achievement in engineering so far?