100+ Junior Engineer Electrical Interview Questions and Answers

Transformers work on the principle of electromagnetic induction. Mineral oil is commonly used in transformers. If oil is not added, the transformer may overheat and fail.

• Transformers work on the principle of electromagnetic induction

• Mineral oil is commonly used in transformers to provide insulation and cooling

• If oil is not added, the transformer may overheat and fail

Different types of cables used for transmissions include coaxial, twisted pair, fiber optic, and ribbon cables.

• Coaxial cables are used for high-frequency transmissions and have a copper core surrounded by insulation and a braided shield.

• Twisted pair cables are used for low-frequency transmissions and have two insulated copper wires twisted together.

• Fiber optic cables use light to transmit data and are made of glass or plastic fibers.

• Ribbon cables are used for internal connect...read more

Generator produces direct current while alternator produces alternating current. Different cables used for transmission include coaxial, twisted pair, and fiber optic cables.

• Generator produces direct current (DC) while alternator produces alternating current (AC)

• Generator uses slip rings and brushes for transmission while alternator uses a commutator

• Different cables used for transmission include coaxial, twisted pair, and fiber optic cables

Ideal transformer is theoretical with no losses, while practical transformer has losses due to resistance, leakage flux, etc.

• Ideal transformer has no losses, while practical transformer has losses due to resistance, leakage flux, hysteresis, and eddy currents

• Ideal transformer has infinite efficiency, while practical transformer has efficiency less than 100%

• Ideal transformer has no voltage drop, while practical transformer has voltage drop due to resistance

• Ideal transformer ha...read more

I have experience in building power transmission systems.

• I have built power transmission systems in my previous job.

• I have worked on projects involving power transmission systems.

• I am familiar with the process of building power transmission systems.

• I have knowledge of the equipment and materials required for power transmission systems.

• I have experience in designing power transmission systems for different environments.

Basics of electrical include understanding circuits, components, and power sources. Foundations of production and maintenance work involve safety, planning, and troubleshooting.

• Basics of electrical include understanding circuits, components, and power sources

• Foundations of production work involve safety, planning, and quality control

• Foundations of maintenance work involve safety, planning, and troubleshooting

• Examples of production work include designing and building electrica...read more

Compressor, fire hydrant system, RO system, cooling towers, lights, VFD and motors output powers are all related to electrical engineering.

• Compressor is a mechanical device that increases the pressure of a gas.

• Fire hydrant system is a network of pipes and valves designed to provide water to firefighters.

• RO system is a water purification technology that uses a semipermeable membrane to remove ions, molecules, and larger particles from drinking water.

• Cooling towers are used to ...read more

The type of electrical machine used in wind turbines for power generation is the induction generator.

• Induction generator is commonly used in wind turbines due to its simplicity, reliability, and low maintenance requirements.

• It operates on the principle of electromagnetic induction to convert mechanical energy from the wind into electrical power.

• Induction generators do not require a separate power source for excitation, making them suitable for variable speed wind turbines.

• Exa...read more

Current transformer is used to measure current while potential transformer is used to measure voltage.

• Current transformer is connected in series with the circuit being measured, while potential transformer is connected in parallel.

• Current transformer steps down the current to a measurable level, while potential transformer steps down the voltage.

• Current transformer is used for protection and metering purposes, while potential transformer is mainly used for metering and contro...read more

Transformers are rated in kVA because it takes into account both active power (KW) and reactive power (KVAR). Transformer losses include copper losses and iron losses.

• Transformers are rated in kVA because they handle both active power (KW) and reactive power (KVAR).

• kVA rating considers the total power (apparent power) that the transformer can handle, including the power needed for magnetizing the core.

• Transformer losses include copper losses (I²R losses) and iron losses (eddy...read more

The emf equation of a transformer relates the induced voltage to the number of turns in the primary and secondary coils.

• The emf equation of a transformer is given by: E = N*dΦ/dt, where E is the induced voltage, N is the number of turns, and dΦ/dt is the rate of change of magnetic flux.

• This equation shows that the induced voltage in a transformer is directly proportional to the number of turns in the coils and the rate of change of magnetic flux.

• The emf equation is important ...read more

Power transformers are used in high voltage transmission systems, while distribution transformers are used in low voltage distribution networks.

• Power transformers are designed for high voltage transmission systems, typically above 33 kV.

• Distribution transformers are used in low voltage distribution networks, typically below 33 kV.

• Power transformers are larger in size and have higher power ratings compared to distribution transformers.

• Power transformers are used to step up or ...read more

Industries use various types of motors depending on their requirements.

• AC motors are commonly used in industries for their efficiency and reliability.

• DC motors are used for applications that require variable speed control.

• Servo motors are used for precise control in robotics and automation.

• Stepper motors are used for precise positioning in CNC machines and robotics.

• Brushless DC motors are used in applications that require high power and efficiency.

• Examples of industries that ...read more

To erect an 8MVA power transformer, follow these steps:

• Prepare the site by leveling the ground and ensuring proper drainage

• Install the transformer foundation and anchor bolts

• Position the transformer on the foundation using a crane

• Connect the transformer to the high voltage and low voltage cables

• Perform insulation resistance tests and verify connections

• Fill the transformer with insulating oil and perform oil tests

• Energize the transformer and monitor its performance

CT Secondary site is shorted to prevent damage to the CT and connected equipment.

• Shorting CT Secondary site prevents high voltage from being induced in the secondary winding.

• It also prevents damage to the CT and connected equipment due to high voltage.

• Shorting is done during CT testing or maintenance.

• Shorting can be done using a shorting link or a shorting switch.

Communications through power lines occur using a technology called Power Line Communication (PLC).

• Power Line Communication (PLC) is a technology that allows data to be transmitted over existing power lines.

• PLC uses the frequency range of the power lines to carry data signals.

• Modulation techniques are used to encode the data onto the power line signals.

• PLC can be used for various applications such as smart grid systems, home automation, and broadband internet access.

• Examples o...read more

Overhead distribution system is a network of electrical lines and equipment used to distribute power from substations to consumers.

• Overhead distribution systems consist of poles, wires, transformers, and insulators.

• They are commonly used in rural areas and older urban areas.

• Maintenance of overhead distribution systems includes regular inspections for damage and vegetation management.

• Examples of overhead distribution systems include power lines running along streets and throug...read more

Power flows from generation to end consumer through a series of interconnected transmission and distribution systems.

• Power is generated at power plants using various sources such as coal, natural gas, nuclear, hydro, wind, or solar energy.

• The generated power is then transmitted over long distances through high-voltage transmission lines to substations.

• At substations, the voltage is reduced and the power is distributed through lower-voltage distribution lines to homes, busines...read more

Transformers are rated in KVA because it indicates the maximum amount of power that can be transferred through the transformer.

• KVA rating is used to determine the maximum amount of power that can be transferred through the transformer

• It takes into account both the voltage and current ratings of the transformer

• KVA rating is important for selecting the appropriate transformer for a given application

• For example, a 100 KVA transformer can handle a maximum power of 100,000 watts

No, magnetic flow meters are not suitable for oil flow measurement due to the lack of conductivity in oil.

• Magnetic flow meters rely on the conductive properties of the fluid to measure flow rate

• Oil is not conductive enough for accurate measurement with a magnetic flow meter

• Alternative flow measurement technologies like ultrasonic or turbine meters are more suitable for oil flow measurement

LT line refers to Low Tension line while HT line refers to High Tension line.

• LT line carries low voltage and is used for domestic and small-scale commercial purposes.

• HT line carries high voltage and is used for industrial and large-scale commercial purposes.

• LT line voltage is typically up to 440 volts, while HT line voltage is above 440 volts.

• LT lines are usually overhead lines, while HT lines can be both overhead and underground.

• Examples of LT lines include household electri...read more

We used different types of circuit breakers at the site depending on the specific requirements.

• We used air circuit breakers (ACBs) for low voltage applications.

• For medium voltage applications, we used vacuum circuit breakers (VCBs) or oil circuit breakers (OCBs).

• In high voltage installations, we used sulfur hexafluoride (SF6) circuit breakers.

• For specialized applications like generator protection, we used differential circuit breakers.

• We also employed electronic circuit break...read more

A transformer is a device that transfers electrical energy between two or more circuits through electromagnetic induction.

• Transformers are used to increase or decrease voltage levels in electrical circuits.

• There are two main types of transformers: step-up transformers and step-down transformers.

• Step-up transformers increase voltage levels, while step-down transformers decrease voltage levels.

• Examples of transformers include power transformers used in electrical substations an...read more

Capacitance is the ability of a body to store an electric charge. Inductance is the ability of a coil to store energy in a magnetic field.

• Capacitance is measured in Farads (F)

• Capacitors are used to store energy in electronic circuits

• Inductance is measured in Henrys (H)

• Inductors are used in electronic circuits to store energy in a magnetic field

• Both capacitance and inductance are important in AC circuits

PI test is a type of transformer testing that measures the insulation resistance and polarization index.

• PI test is performed to determine the condition of insulation in transformers.

• It involves measuring the insulation resistance and polarization index of the transformer.

• The insulation resistance is measured by applying a DC voltage to the transformer winding and measuring the current.

• The polarization index is the ratio of the insulation resistance at 10 minutes to the insula...read more

Inverter works on the principle of converting DC power to AC power.

• Inverter takes DC power input and converts it into AC power output.

• It uses electronic components like transistors and capacitors to switch the direction of current flow.

• The output waveform can be modified to produce sine wave, square wave, or modified sine wave.

• Common applications include solar power systems, UPS units, and electric vehicles.

Network theorems and types of towers used in transmission and distribution lines are important concepts in electrical engineering.

• Network theorems include Thevenin's theorem, Norton's theorem, and Superposition theorem.

• Types of towers used in transmission and distribution lines include suspension towers, tension towers, and dead-end towers.

• Suspension towers are used for long spans, tension towers for shorter spans, and dead-end towers for the end of a line.

• The choice of tower...read more

To start a DC motor, apply a voltage to the motor terminals.

• Connect the positive terminal of the power supply to the motor's positive terminal.

• Connect the negative terminal of the power supply to the motor's negative terminal.

• Gradually increase the voltage to avoid sudden jerks or damage to the motor.

• Ensure the motor is properly lubricated and free from any mechanical obstructions before starting.

A current transformer is a type of instrument transformer used to measure alternating current.

• Used to step down high currents to a lower, more manageable level for measurement

• Consists of a primary winding and a secondary winding

• Secondary winding is connected to measuring instruments or protective relays

• Provides accurate current measurement without affecting the main circuit

We used a stationary type batching plant at the site.

• We used a stationary type batching plant for our construction project.

• The stationary batching plant had a higher production capacity compared to mobile plants.

• It was equipped with multiple storage bins for different types of aggregates.

• The plant had a conveyor belt system to transfer the aggregates to the mixer.

• We used this type of batching plant because it provided consistent and high-quality concrete.

Electricity is the flow of electrons through a conductor.

• Electricity is a form of energy that powers most of our modern devices.

• It is generated by various sources such as coal, wind, solar, and hydro power.

• Electricity can be stored in batteries and used later.

• It can be dangerous if not handled properly and can cause electric shocks or fires.

• Electricity is measured in units of volts, amps, and watts.

Transformers are tested for various parameters to ensure their proper functioning.

• Measurement of winding resistance

• Measurement of voltage ratio and turns ratio

• Measurement of insulation resistance

• Measurement of no-load current and losses

• Measurement of load losses and impedance voltage

• Measurement of temperature rise

• Dielectric tests

A resistor is an electronic component that limits the flow of electric current, while resistance is the measure of opposition to current flow.

• Resistor is a physical component made of materials like carbon or metal, while resistance is a property of a material to resist the flow of electricity.

• Resistor is measured in ohms (Ω), while resistance is also measured in ohms.

• Resistors are used in electronic circuits to control current flow, while resistance is inherent in all materia...read more

A potential transformer is a type of instrument transformer used to step down high voltage to a lower, safer voltage for measurement or control purposes.

• Used to step down high voltage to a lower voltage for measurement or control purposes

• Provides accurate voltage measurements for meters and relays

• Commonly used in power systems for protection and metering applications

Earthing is the process of connecting electrical equipment or installations to the earth to prevent electric shock and protect against electrical faults.

• Earthing involves creating a connection between the electrical system and the earth.

• It is done by burying a metal conductor, such as a copper rod, in the ground.

• The metal conductor is connected to the electrical system using a wire or cable.

• Earthing provides a path for the flow of excess electrical current to the ground, prev...read more

The unit of inductor is Henry (H)

• The unit of inductor is named after American scientist Joseph Henry

• It is represented by the symbol 'H'

• 1 Henry is equal to 1 volt-second per ampere

My weak point is lack of experience in certain areas, but my strong point is my ability to quickly learn and adapt.

• Weak point: Lack of experience in certain areas such as advanced circuit design

• Strong point: Quick learner and adaptable, able to pick up new skills and knowledge easily

• Example: While I may not have experience with a specific software program, I am confident in my ability to quickly learn and become proficient in using it

UPS systems can be connected in parallel for redundancy and increased capacity.

• Ensure that the UPS systems have the same voltage and frequency ratings.

• Connect the output of each UPS system to a common bus bar.

• Use a synchronization module to ensure that the UPS systems are in phase with each other.

• Ensure that the load is evenly distributed between the UPS systems.

• Perform regular maintenance and testing to ensure proper operation.

• Example: Two 10 kVA UPS systems can be connected...read more

Solar energy conversion is the process of converting sunlight into electricity or heat using solar panels or solar thermal systems.

• Solar energy conversion can be achieved through photovoltaic (PV) cells, which directly convert sunlight into electricity.

• Solar thermal systems use mirrors or lenses to concentrate sunlight onto a small area, generating heat that can be used to produce electricity or heat water.

• Solar energy conversion is a sustainable and renewable energy source t...read more

There are two types of single phase motors: AC motors and DC motors.

• Single phase AC motors include split-phase motors, capacitor-start motors, and shaded-pole motors.

• Single phase DC motors include universal motors and series motors.

• AC motors are more commonly used in household appliances, while DC motors are used in power tools and small appliances.

• Single phase motors are generally less efficient than three phase motors and are used for smaller applications.

• Single phase motor...read more

A Single Line Diagram (SLD) is a simplified representation of a 33/11 Kv substation.

• SLD shows the electrical components and connections in a substation

• It includes transformers, circuit breakers, busbars, and other equipment

• Lines are drawn to represent the flow of electricity between components

• Symbols and labels are used to indicate the type and rating of each component

• Example: A 33/11 Kv substation SLD may show a 33 Kv incoming line, a transformer, and multiple 11 Kv outgoing...read more

DC motors and AC motors are two types of electric motors commonly used in various applications.

• DC motors operate using direct current, while AC motors operate using alternating current.

• DC motors are typically used in applications that require high torque at low speeds, such as in electric vehicles and robotics.

• AC motors are commonly used in household appliances, industrial machinery, and HVAC systems.

• DC motors are simpler in construction and easier to control compared to AC m...read more

AIS stands for Air Insulated Substation, while GIS stands for Gas Insulated Substation.

• AIS substations use air as the insulating medium for the switchgear, while GIS substations use sulfur hexafluoride (SF6) gas.

• GIS substations are more compact and require less space compared to AIS substations.

• AIS substations are generally cheaper to build and maintain than GIS substations.

• GIS substations are more reliable and have lower maintenance requirements due to the sealed gas-insulat...read more

The amount of current that the human body can withstand varies depending on various factors.

• The resistance of the human body plays a significant role in determining the amount of current it can withstand.

• Dry skin has higher resistance compared to wet or broken skin, making it more resistant to electric shock.

• The path of the current through the body also affects the severity of the shock.

• The duration of exposure to the current is another important factor.

• The frequency of the c...read more

Yes, as a Junior Engineer Electrical, you should be physically capable of climbing a 92 meter wind turbine.

• Physical fitness is important for climbing such heights

• Proper safety training and equipment are necessary

• Experience in working at heights is beneficial

The size of transformers used at the site varied depending on the specific requirements of the project.

• Transformers used at the site were of different sizes based on the power demand of the electrical system.

• For smaller projects, transformers with a capacity of around 100 kVA were used.

• For medium-sized projects, transformers with a capacity ranging from 250 kVA to 500 kVA were used.

• For larger projects, transformers with a capacity exceeding 1000 kVA were used.

• The size of the ...read more

Current is the flow of electric charge in a circuit.

• Current is measured in Amperes (A).

• It is the rate of flow of electric charge past a point in a circuit.

• Current can be either direct current (DC) or alternating current (AC).

• Examples: A light bulb draws current from a power source to produce light. A fan motor requires current to spin.