900+ Electrical Engineer Interview Questions and Answers

Transformer ratings are usually expressed in terms of voltage, current, and power.

• Voltage rating

• Current rating

• Power rating

• kVA rating

• Frequency rating

A 3-phase 4 wire system is a type of electrical system commonly used for power distribution.

• Consists of three conductors carrying alternating current at the same frequency, with a fourth neutral conductor

• Provides a more balanced and efficient power distribution compared to single-phase systems

• Commonly used in industrial and commercial applications for higher power requirements

• Example: Used in large factories, office buildings, and data centers

Current is the flow of electric charge in a circuit, while voltage is the force that drives this flow.

• Current is measured in amperes (A) and represents the rate of flow of electric charge.

• Voltage is measured in volts (V) and represents the electric potential difference between two points in a circuit.

• Current is analogous to the flow of water in a pipe, while voltage is analogous to the pressure that pushes the water through the pipe.

• In a simple circuit, current flows from the...read more

High voltage transmission lines typically use ACSR conductors for 220 kV and 400 kV systems.

• ACSR (Aluminum Conductor Steel Reinforced) conductors are commonly used for high voltage transmission lines

• ACSR conductors consist of a central steel core surrounded by aluminum strands

• The steel core provides strength and support, while the aluminum strands conduct electricity

• ACSR conductors are lightweight, strong, and have good conductivity, making them ideal for high voltage applica...read more

The protection system of a power transformer ensures its safe operation by detecting and mitigating faults.

• Protection systems monitor various parameters of the transformer such as temperature, oil level, and winding currents.

• Differential protection is commonly used to detect internal faults by comparing the currents entering and leaving the transformer.

• Buchholz relay is used to detect and isolate faults in the oil-filled transformer by sensing gas accumulation.

• Overcurrent pro...read more

The phase to phase clearance in a 33kV line is typically around 1 meter.

• Phase to phase clearance in a 33kV line is usually around 1 meter to ensure safety and prevent electrical arcing.

• The clearance distance may vary based on specific regulations and standards in different regions.

• Proper clearance is important to prevent short circuits and ensure reliable power transmission.

• Clearance distances are determined based on factors such as voltage level, environmental conditions, an...read more

Distribution lines are electrical power lines that carry electricity from a substation to consumers.

• Distribution lines are part of the electrical grid infrastructure.

• They transmit electricity at lower voltages compared to transmission lines.

• Distribution lines deliver power to homes, businesses, and other end-users.

• They can be overhead lines or underground cables.

• Distribution lines often have transformers to step down the voltage for consumer use.

A transformer is a device that transfers electrical energy between two or more circuits through electromagnetic induction. A stabilizer is a device that maintains a constant voltage output despite fluctuations in the input voltage.

• Transformers transfer electrical energy between circuits through electromagnetic induction.

• Stabilizers maintain a constant voltage output despite fluctuations in the input voltage.

• Transformers are commonly used in power distribution systems to step ...read more

DOL starter is a direct online starter used to start and stop motors. VFD is a variable frequency drive used to control motor speed.

• DOL starter is a simple and cost-effective method of starting motors

• It provides full voltage to the motor during starting

• VFD is used to control the speed of the motor by varying the frequency of the power supplied to the motor

• It is more efficient than other methods of speed control

• VFDs are commonly used in HVAC systems, pumps, and conveyor belts

Uniformity factor is the ratio of the minimum illuminance to the average illuminance on a surface. Maintenance factor is the ratio of the illuminance after a period of time to the initial illuminance.

• Uniformity factor is important in lighting design to ensure consistent lighting levels across a space.

• A higher uniformity factor indicates more even lighting distribution.

• Maintenance factor accounts for factors like dirt accumulation and lamp depreciation over time.

• It is used to ...read more

To protect a transformer, measures such as overcurrent protection, temperature monitoring, and proper grounding should be implemented. VFD stands for Variable Frequency Drive, a device used to control the speed of an electric motor.

• Implement overcurrent protection to prevent excessive current flow through the transformer.

• Monitor the temperature of the transformer using temperature sensors to prevent overheating.

• Ensure proper grounding of the transformer to protect against ele...read more

Transformers work on the principle of electromagnetic induction to transfer electrical energy between two or more circuits.

• Transformers have two coils of wire, known as the primary and secondary coils.

• When an alternating current flows through the primary coil, it creates a changing magnetic field.

• This changing magnetic field induces a voltage in the secondary coil, transferring electrical energy between the two coils.

• The ratio of the number of turns in the primary and seconda...read more

The major parts in a power transformer include the core, windings, insulation, cooling system, and tap changer.

• Core: Provides a path for magnetic flux and is usually made of laminated steel sheets.

• Windings: Consist of primary and secondary coils that transfer electrical energy.

• Insulation: Prevents electrical leakage and ensures safety.

• Cooling System: Keeps the transformer within operating temperature limits, commonly using oil or air.

• Tap Changer: Allows adjustment of the tran...read more

Lenz's law states that the direction of an induced current in a conductor is always such that it opposes the change in magnetic field that produced it.

• Lenz's law is a fundamental law of electromagnetism.

• It is named after Heinrich Lenz, a Russian physicist.

• It is used to determine the direction of induced current in a conductor.

• The law is based on the principle of conservation of energy.

• It is used in many applications, including electric motors and generators.

Yes, OLTC is always connected in the HT voltage side.

• OLTC stands for On-Load Tap Changer.

• It is a device used in electrical power transformers to regulate the voltage level.

• OLTC is typically connected on the high voltage (HT) side of the transformer.

• It allows for tap changing while the transformer is energized and under load.

• By changing the tap position, the OLTC can adjust the transformer's output voltage.

• This helps to compensate for variations in the input voltage or load co...read more

The pressure in a VCB in vacuum interrupter remains around 10^-6 to 10^-7 torr.

• The pressure in a VCB in vacuum interrupter is typically maintained at around 10^-6 to 10^-7 torr.

• This low pressure helps in preventing arcing and ensures efficient interruption of the circuit.

• Maintaining a vacuum in the interrupter chamber helps in improving the dielectric strength of the medium.

• Examples of VCBs with vacuum interrupters include Siemens 3AH4 and ABB VD4.

Single mode fiber optic cable has a smaller core size and allows only one mode of light to propagate, while multimode fiber optic cable has a larger core size and allows multiple modes of light to propagate.

• Single mode fiber optic cable has a core size of 8-10 microns, while multimode fiber optic cable has a core size of 50-62.5 microns.

• Single mode fiber optic cable provides higher bandwidth and longer transmission distances compared to multimode fiber optic cable.

• Single mode...read more

ELCB stands for Earth Leakage Circuit Breaker. It is a safety device used to protect electrical circuits from electric shock.

• ELCB is designed to detect small leakage currents that may occur due to insulation failure or faulty wiring.

• When an ELCB detects a leakage current, it quickly cuts off the power supply to prevent electric shock.

• ELCBs are commonly used in homes, offices, and industries to ensure electrical safety.

• There are two types of ELCBs: voltage-operated ELCB and cu...read more

DG sets have various protection mechanisms to ensure safe and efficient operation.

• Overload protection

• Short circuit protection

• Under/over voltage protection

• Over/under frequency protection

• Reverse power protection

• Earth fault protection

• Cooling system protection

• Fuel system protection

Alternator and transformer protection systems are essential for preventing damage and ensuring safe operation.

• Alternator protection systems typically include overcurrent, overvoltage, and reverse power protection to safeguard the alternator from damage.

• Transformer protection systems often involve differential protection, overcurrent protection, and temperature monitoring to prevent overheating and insulation breakdown.

• Both systems may also incorporate alarm systems and automa...read more

Transformer protection includes overcurrent, overvoltage, differential, earth fault, and thermal protection.

• Overcurrent protection prevents damage due to excessive current flow.

• Overvoltage protection prevents damage due to excessive voltage.

• Differential protection detects internal faults and isolates the transformer from the system.

• Earth fault protection detects faults between the transformer winding and earth.

• Thermal protection prevents damage due to excessive temperature.

• Ex...read more

DP in Siemens communication stands for Distributed Peripherals.

• DP is a communication protocol used by Siemens for connecting distributed peripherals to a central control system.

• It allows for real-time data exchange between the peripherals and the control system.

• DP is commonly used in industrial automation applications.

• Examples of DP communication modules include DP/DP couplers and DP slaves.

An electric motor is a device that converts electrical energy into mechanical energy to produce motion.

• Electric motors use electromagnetic fields to generate force and motion.

• They are commonly used in various applications such as industrial machinery, household appliances, and electric vehicles.

• Examples include AC motors, DC motors, and brushless motors.

Predictive maintenance uses data and analytics to predict when equipment failure may occur, while preventive maintenance involves regularly scheduled maintenance to prevent breakdowns.

• Predictive maintenance uses data and analytics to predict when equipment failure may occur

• Preventive maintenance involves regularly scheduled maintenance to prevent breakdowns

• Predictive maintenance is more cost-effective as it allows for maintenance to be performed only when needed

• Preventive mai...read more

Transformer efficiency is maximum at 50% load. Working principle involves electromagnetic induction.

• Transformer efficiency is highest at 50% load

• Efficiency decreases with increasing or decreasing load

• Working principle involves electromagnetic induction

• Transformers can step up or step down voltage

• Transformers are used in power transmission and distribution

Electrical lightning protection design codes and standards are guidelines that ensure the safety and effectiveness of lightning protection systems.

• National Fire Protection Association (NFPA) 780 is a widely recognized standard for lightning protection design.

• International Electrotechnical Commission (IEC) 62305 is another commonly used standard for lightning protection.

• These codes and standards provide guidelines for the design, installation, inspection, and maintenance of li...read more

Precommissioning tests of transformers are essential to ensure their proper functioning.

• Insulation resistance test

• Turns ratio test

• Vector group test

• Winding resistance test

• Magnetizing current test

• No-load loss and excitation current test

• Load loss and impedance voltage test

A motor is an electrical device that converts electrical energy into mechanical energy. There are various types of motors.

• Motors are used in various applications such as industrial machinery, household appliances, and automobiles.

• The most common types of motors are DC motors, AC motors, and stepper motors.

• DC motors are used in applications that require variable speed control, such as electric vehicles and robotics.

• AC motors are used in applications that require constant speed...read more

Star delta is used in electrical engineering to reduce starting current and protect motors.

• Star delta connection is used for induction motors.

• It reduces the starting current by a factor of √3.

• It helps in reducing voltage drop during motor starting.

• It protects the motor from excessive current and overheating.

• It is commonly used in applications where the motor needs to start with a low current.

SMPS stands for Switched Mode Power Supply, a type of power supply that uses switching devices to convert electrical power.

• SMPS is more efficient than traditional linear power supplies

• It uses high-frequency switching to convert AC to DC power

• It is commonly used in electronic devices such as computers, TVs, and mobile phones

• Examples of SMPS topologies include flyback, forward, and push-pull

• SMPS can be designed for different output voltages and currents

A relay is an electrically operated switch that uses an electromagnet to mechanically control the opening and closing of contacts.

• Relays are commonly used in electrical systems to control high-power devices with low-power signals.

• They can be used to control motors, lights, solenoids, and other electrical components.

• Relays have an input coil that generates a magnetic field when current flows through it, causing the contacts to open or close.

• They provide isolation between the c...read more

Copper or aluminum conductors are used in 132KV transmission lines for their high conductivity and low resistance.

• Copper and aluminum are the most commonly used conductors.

• Copper has higher conductivity but is more expensive than aluminum.

• Aluminum has lower conductivity but is lighter and cheaper than copper.

• The choice of conductor depends on factors such as cost, weight, and transmission distance.

• Other factors such as corrosion resistance and mechanical strength also play a ...read more

Chemical earthing involves the use of chemicals to improve conductivity and reduce soil resistivity.

• Normal earthing involves the use of a metal rod or plate buried in the ground to provide a low resistance path for fault current.

• Chemical earthing involves the use of chemicals such as bentonite, salt, and charcoal to improve conductivity and reduce soil resistivity.

• Chemical earthing is more effective in areas with high soil resistivity or where the soil is rocky or sandy.

• Norma...read more

To calculate the size of a capacitor to improve power factor (PF), you need to determine the reactive power and the desired power factor.

• Calculate the reactive power by multiplying the apparent power by the sine of the angle between the current and voltage waveforms.

• Determine the desired power factor, which is the cosine of the angle between the current and voltage waveforms.

• Use the formula: Capacitance (in Farads) = Reactive Power (in Volt-Amperes Reactive) / (2 * π * Freque...read more

Power factor is the ratio of real power to apparent power in an AC circuit. VFD stands for Variable Frequency Drive. AC motors run on alternating current while DC motors run on direct current.

• Power factor is a measure of how effectively electrical power is being used in a circuit.

• It is calculated by dividing the real power (in watts) by the apparent power (in volt-amperes).

• A power factor of 1 indicates that all the power is being used effectively, while a power factor less th...read more

VFD has various control modes like V/F control, vector control, sensorless vector control, torque control, etc.

• V/F control is the most basic control mode

• Vector control provides better speed and torque control

• Sensorless vector control eliminates the need for an encoder

• Torque control is used for applications that require precise torque control

• Other control modes include open-loop control, closed-loop control, etc.

The inputs from site civil members are crucial for executing the final plan as they provide valuable on-ground insights and feedback.

• Site civil members provide information on site conditions, such as terrain, soil type, and existing structures.

• They may also offer suggestions for optimizing the plan based on their expertise and experience.

• Feedback from site civil members can help identify potential challenges or risks that need to be addressed in the final plan.

• Collaboration b...read more

Switchgear is an electrical equipment that controls, protects and isolates electrical circuits. Drive is a mechanism that controls the speed and torque of an electrical motor.

• Switchgear is used to protect electrical equipment from damage caused by short circuits and overloads.

• It is also used to isolate electrical circuits for maintenance purposes.

• Drive is used to control the speed and torque of an electrical motor.

• It is commonly used in industrial applications such as conveyo...read more

Before starting electrical activity, I ensure all safety precautions are in place and equipment is functioning properly.

• Perform a safety check on all equipment and tools

• Verify that all connections are secure and wires are properly insulated

• Double check the circuit design and calculations for accuracy

• Ensure proper grounding is in place to prevent electrical hazards

Different types of protection are used in a substation to ensure safety and reliability.

• Overcurrent protection: Protects against excessive current flow.

• Overvoltage protection: Safeguards against high voltage surges.

• Differential protection: Detects faults by comparing currents entering and leaving the substation.

• Distance protection: Protects transmission lines based on the distance to the fault.

• Ground fault protection: Detects faults to ground and prevents electrical shock haz...read more

Fanuc has different parameters for various functions such as motion control, spindle control, and tool management.

• Fanuc parameters are used to control various functions such as motion control, spindle control, and tool management.

• Parameters can be set to adjust the speed, acceleration, and deceleration of the machine.

• Fanuc parameters can also be used to set up alarms and diagnostic messages.

• Examples of Fanuc parameters include 1000 for motion control, 3000 for spindle control...read more

Load list is a document that lists all the electrical loads in a building or facility.

• It includes details such as the name of the load, its location, power rating, and voltage requirements.

• Load list is used to determine the total power demand of the building and to design the electrical system accordingly.

• It is also used for maintenance and troubleshooting purposes.

• Examples of loads that may be included in a load list are lighting fixtures, HVAC systems, elevators, and motors...read more

Armature voltage control involves changing the voltage applied to the armature of a DC motor to control its speed, while field control involves changing the field current to control the motor's speed.

• Armature voltage control adjusts the voltage applied to the armature winding of a DC motor to control its speed

• Field control adjusts the field current in the motor to control its speed

• Armature voltage control is more common in applications where precise speed control is required,...read more

Transformer parts include core, windings, insulation, tap changer, and cooling system.

• Core: magnetic material that provides a path for the magnetic flux

• Windings: conductors that carry the electrical current

• Insulation: material that separates the windings and core to prevent short circuits

• Tap changer: device that adjusts the number of turns in the windings to regulate voltage

• Cooling system: dissipates heat generated by the transformer

• Examples: bushings, conservator, breather, ...read more

I have experience working on various types of vessels including cargo ships, tankers, and offshore vessels.

• Worked on cargo ships, tankers, and offshore vessels

• Experience in electrical maintenance and repair

• Familiarity with electrical systems on board vessels

• Knowledge of safety regulations and procedures

• Collaborated with other engineers and crew members

The height of a dB location on a wall depends on the specific requirements of the project or application.

• The height of a dB location on a wall is typically determined by the specific needs of the project or application.

• Factors such as the type of equipment being installed, the purpose of the dB location, and the layout of the space will influence the height chosen.

• For example, in a control room setting, dB locations may be placed at eye level for easy access and visibility.

• In...read more

Load flow can be solved using various methods.

• Gauss-Seidel method

• Newton-Raphson method

• Fast decoupled method

• DC load flow method

• AC load flow method

• Continuation power flow method