100+ Electrical Design Engineer Interview Questions and Answers

Unbalanced protection in electrical systems is a type of protection that detects and responds to imbalances in current or voltage levels.

• Unbalanced protection is used to detect faults such as phase-to-phase or phase-to-ground faults in electrical systems.

• It helps prevent damage to equipment and ensures the safety of personnel by quickly isolating the faulty section of the system.

• Examples of unbalanced protection devices include ground fault relays and differential relays.

• Thes...read more

Designing an electrical system involves determining power requirements, selecting components, creating schematics, and ensuring safety.

• Determine power requirements based on the load and usage

• Select appropriate components such as transformers, circuit breakers, and wires

• Create schematics and diagrams to illustrate the system

• Ensure safety by following codes and regulations

• Consider maintenance and future expansion needs

The IP rating of a panel refers to its level of protection against solids and liquids. Panels can be separated by physical barriers or electrical insulation.

• IP rating indicates the degree of protection provided by a panel against dust and water. Higher IP ratings offer better protection.

• Separation of panels can be achieved through physical barriers such as walls, partitions, or enclosures.

• Electrical insulation is another form of separation, where panels are isolated from each...read more

NEC codes dictate wire sizing, load calculation, breaker sizing, and disconnect sizing for electrical design.

• NEC 310-16 provides guidelines for wire sizing based on ampacity and temperature rating

• NEC 220 provides guidelines for load calculation based on the type of building and its intended use

• NEC 240 provides guidelines for breaker sizing based on the wire size and load calculation

• NEC 430 provides guidelines for disconnect sizing based on the motor's full load current

• Complia...read more

Circuit breakers are of different types based on their voltage levels, construction, and applications.

• Based on voltage levels: low voltage, medium voltage, and high voltage circuit breakers

• Based on construction: air circuit breakers, oil circuit breakers, vacuum circuit breakers, and SF6 circuit breakers

• Based on applications: residential, commercial, and industrial circuit breakers

• Other types: molded case circuit breakers, miniature circuit breakers, ground fault circuit inte...read more

The Power & Control Circuit of Star Delta Feeder is a common circuit used in electrical engineering.

• The circuit consists of a power circuit and a control circuit.

• The power circuit includes a three-phase AC motor, a contactor, and overload relays.

• The control circuit includes a timer, a contactor, and a push button station.

• The circuit is used to reduce the starting current of the motor.

• During starting, the motor is connected in star configuration, and then switched to delta con...read more

Power and control wiring of star delta starter involves connecting the motor to the power supply and control circuit using a specific wiring diagram.

• Power wiring involves connecting the three-phase power supply to the motor through the main contactor.

• Control wiring involves connecting the control circuit to the motor through the timer and the star-delta contactor.

• During starting, the motor is connected in star configuration to reduce the starting current and then switched to ...read more

I have experience with Siemens S7-1200 PLC, Wonderware InTouch SCADA, and ABB ACS550 VFD.

• Siemens S7-1200 PLC

• Wonderware InTouch SCADA

• ABB ACS550 VFD

Transformer sizing involves calculating the required power capacity based on load demands and application requirements.

• Determine the total load in kilowatts (kW) or kilovolt-amperes (kVA) that the transformer will serve.

• Consider the load diversity factor, which accounts for the fact that not all loads will be at maximum simultaneously.

• Calculate the transformer capacity using the formula: Transformer Size (kVA) = Total Load (kW) / Power Factor.

• Include future expansion needs by...read more

The recommended distance between two cable trays varies based on installation and safety standards.

• Typically, a distance of 300 mm (12 inches) is recommended for proper airflow and maintenance access.

• For larger cables, a distance of 450 mm (18 inches) may be necessary to prevent overheating.

• Local codes and standards, such as NEC or IEC, should always be consulted for specific requirements.

• Consider the type of cables being used; power cables may require more spacing than commu...read more

Maintenance factor is a multiplier used in lighting design to account for the decrease in light output over time due to dirt, aging, and other factors.

• Maintenance factor is typically a value between 0 and 1, with 1 indicating no decrease in light output over time.

• It is used to adjust the initial illuminance level calculated for a space to account for the decrease in light output over the life of the lighting system.

• Factors that can affect maintenance factor include dirt accum...read more

Uniformity factor is a measure of how evenly distributed light is in a given space.

• Uniformity factor is calculated by dividing the minimum illuminance level by the average illuminance level in a space.

• A higher uniformity factor indicates more even lighting distribution.

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

• For example, in an office setting, a uniformity factor of 0.7 or higher is typically desired.

SCCR stands for Short-Circuit Current Rating.

• SCCR is a measure of the maximum amount of current that a device or system can safely withstand during a short circuit.

• It is an important consideration in electrical design to ensure the protection of equipment and personnel.

• SCCR is typically expressed in amperes (A) and is determined through testing or calculations.

• It helps in selecting appropriate protective devices such as fuses, circuit breakers, or disconnect switches.

• For exam...read more

The process for calculating power load involves determining the electrical demand of a system or device.

• Identify all electrical devices and their power ratings in the system.

• Calculate the power consumption of each device by multiplying its voltage and current.

• Sum up the power consumption of all devices to get the total power load.

• Consider factors like power factor and diversity to account for variations in power usage.

• Ensure the power supply can handle the calculated power lo...read more

Cable size calculation is based on current carrying capacity, voltage drop, and length of the cable.

• Determine the maximum current that the cable will carry

• Calculate the voltage drop based on the length of the cable and the current

• Select a cable size that can handle the current and voltage drop requirements

• Consider factors such as ambient temperature and installation method

• Use cable sizing charts or software for accurate calculations

Single line diagram shows the electrical system in a simplified form, while a schematic diagram shows the detailed electrical connections and components.

• Single line diagram is used for overall system understanding and planning.

• Schematic diagram is used for detailed design and troubleshooting.

• Single line diagram shows only the main components and connections, while schematic diagram shows all components and connections.

• Single line diagram is easier to read and understand, whil...read more

HRC fuse stands for High Rupturing Capacity fuse. It is a type of fuse that is designed to safely interrupt high fault currents.

• HRC fuse is used in electrical systems to protect against overcurrents and short circuits.

• It has a high breaking capacity, which means it can safely interrupt high fault currents without causing damage.

• The fuse contains a fuse element made of a material that can withstand high temperatures and currents.

• When a fault occurs, the fuse element melts and ...read more

A headlight circuit with a relay and switch is used to control the headlights of a vehicle.

• The switch is used to turn the headlights on and off.

• The relay is used to control the high and low beams of the headlights.

• When the switch is turned on, power is sent to the relay, which then switches between the high and low beams.

• The relay also protects the switch from high current.

• The circuit should include fuses to protect against short circuits and overloads.

Integrating an electrical system involves designing, testing, and implementing a cohesive system that meets the required specifications.

• Identify the components and subsystems that need to be integrated

• Design a schematic diagram to show how the components will be connected

• Test the system to ensure it meets the required specifications

• Implement the system and ensure it is properly installed and commissioned

• Provide documentation and training to users

Various software tools are used for electrical design engineering.

• CAD software like AutoCAD, SolidWorks, and CATIA for creating 2D and 3D models

• Simulation software like MATLAB, PSCAD, and ETAP for analyzing and testing designs

• Programming software like LabVIEW and C++ for developing control systems

• Project management software like MS Project for scheduling and tracking progress

Calculation of cable size and busbar size is crucial for electrical design engineers.

• Cable size calculation involves determining the current carrying capacity of the cable and selecting the appropriate size based on the load requirements.

• Busbar size calculation involves determining the current carrying capacity of the busbar and selecting the appropriate size based on the load requirements.

• Factors to consider when calculating cable and busbar size include voltage drop, ambien...read more

AutoCAD has various tools for different purposes such as drawing, editing, and annotation.

• Drawing tools: line, circle, arc, rectangle, polygon, etc.

• Editing tools: move, copy, rotate, scale, mirror, etc.

• Annotation tools: text, dimension, hatch, leader, etc.

• Miscellaneous tools: layer, block, attribute, inquiry, etc.

Pragati Electricals is a company that specializes in electrical design and engineering services.

• Provides electrical design and engineering services

• Offers solutions for power distribution, lighting, and control systems

• Works with clients in various industries such as commercial, industrial, and residential

• Has a team of experienced electrical engineers and designers

• Uses advanced software and technology to ensure high-quality designs and efficient project management

EPC stands for Engineering, Procurement, and Construction. EPCIC stands for Engineering, Procurement, Construction, Installation, and Commissioning. FEED stands for Front End Engineering Design.

• EPC projects involve the design, procurement, and construction of a project by a single contractor.

• EPCIC projects include installation and commissioning in addition to the EPC scope.

• FEED projects focus on the initial engineering and design phase before detailed design and construction ...read more

Reflection index in rooms refers to the amount of sound reflected off surfaces within a room.

• Reflection index is important in determining the acoustics of a room.

• High reflection index can lead to echoes and reverberation.

• Materials like concrete and glass have high reflection index, while soft materials like carpets and curtains have low reflection index.

Clearance from signals in front and back side is important for safety and efficient operation.

• Clearance refers to the minimum distance required between the signals and any surrounding objects or structures.

• It ensures that there is no interference or obstruction to the signals' visibility or functionality.

• Clearance requirements may vary depending on the specific signal type and its intended purpose.

• For example, in traffic signal design, clearance is crucial to ensure proper vi...read more

Yes, I have experience using flow meters in various projects.

• I have used flow meters to measure the flow rate of liquids or gases in different systems.

• I am familiar with different types of flow meters such as electromagnetic, ultrasonic, and turbine.

• I have calibrated and maintained flow meters to ensure accurate measurements.

• I have integrated flow meters into control systems for process automation.

• I have troubleshooted flow meter issues to ensure proper functionality.

Circuit breakers are selected based on voltage, current rating, interrupting capacity, and application.

• Voltage rating should be equal to or greater than the system voltage

• Current rating should be selected based on the maximum current expected in the circuit

• Interrupting capacity should be sufficient to interrupt the maximum fault current

• Application-specific requirements such as environmental conditions and type of load should also be considered

• Examples of circuit breaker types...read more

Designing a transformer room involves considering safety, space requirements, ventilation, and electrical codes.

• Ensure proper ventilation to prevent overheating of transformers

• Follow electrical codes and regulations for clearances and access

• Provide adequate space for maintenance and operation of transformers

• Consider safety measures such as fire protection and emergency shutdown systems

The single and three phase power equations are fundamental formulas used in electrical engineering.

• Single phase power equation: P = V * I * cos(theta)

• Three phase power equation: P = sqrt(3) * V * I * cos(theta)

• Where P is power in watts, V is voltage in volts, I is current in amps, and cos(theta) is the power factor

• The square root of 3 in the three phase equation accounts for the phase shift between the three phases

Type 2 coordination is a method used in electrical engineering to ensure that a downstream circuit breaker will trip before an upstream breaker in the event of a fault.

• Type 2 coordination involves selecting circuit breakers with specific characteristics to prevent cascading trips during a fault.

• It ensures that the downstream breaker will trip first to isolate the fault, protecting the upstream breaker and preventing unnecessary downtime.

• Examples of devices used in type 2 coor...read more

To start the design of a motor, one must first determine the requirements, select the appropriate motor type, and then proceed with the design process.

• Determine the requirements of the motor, such as power output, speed, torque, and operating conditions.

• Select the appropriate motor type based on the requirements, such as DC motor, AC motor, stepper motor, or servo motor.

• Consider factors like efficiency, size, cost, and control requirements when choosing the motor type.

• Design ...read more

Relay protections are devices used to detect abnormal conditions in electrical systems and isolate them to prevent damage.

• Relay protections are used to monitor electrical parameters such as voltage, current, frequency, and phase angle.

• They are designed to trip a circuit breaker or disconnect a faulty part of the system when abnormal conditions are detected.

• Examples of relay protections include overcurrent relays, differential relays, distance relays, and frequency relays.

DOL starter directly connects the motor to the power supply, while Star-Delta starter initially connects the motor in star configuration before switching to delta configuration.

• DOL starter provides full voltage to the motor from the start, causing high starting current and torque.

• Star-Delta starter reduces the starting current and torque by initially connecting the motor in star configuration, then switching to delta configuration.

• DOL starter is simpler and cheaper compared t...read more

Microgrid is a localized group of electricity sources and loads that normally operates connected to and synchronous with the traditional centralized grid.

• Microgrid is a small-scale power grid that can operate independently or in conjunction with the main power grid.

• It can include distributed energy resources like solar panels, wind turbines, and batteries.

• Microgrids are often used to increase energy reliability, reduce costs, and integrate renewable energy sources.

• As an elect...read more

Design calculations for transformer, cable, and DG involve determining appropriate sizing based on load requirements and safety factors.

• Calculate transformer size based on load requirements and efficiency ratings

• Determine cable size based on current carrying capacity and voltage drop considerations

• Size DG based on total load demand and backup power requirements

• Consider safety factors such as short circuit protection and overload capacity

• Ensure proper coordination between tran...read more

A diode is a semiconductor device that allows current to flow in one direction only. It is used in circuits to control the direction of current flow and to rectify AC to DC.

• Diodes are used to protect circuits from reverse polarity, preventing damage to sensitive components.

• They are used in rectifier circuits to convert AC voltage to DC voltage, such as in power supplies.

• Diodes are also used in signal processing circuits, such as in radio frequency detectors.

• They can be used i...read more

Emergency services are designed by considering various factors such as response time, communication systems, equipment, and training.

• Consider response time as a crucial factor in designing emergency services.

• Develop effective communication systems to ensure quick and accurate information exchange.

• Equip emergency services with necessary tools and equipment for efficient operations.

• Provide comprehensive training to emergency service personnel to handle various situations effect...read more

Tertiary winding in Auto Transformer is used to provide a third output voltage level.

• Tertiary winding allows for three different output voltage levels to be obtained from the transformer.

• It can be used for applications where multiple voltage levels are required, such as in power distribution systems.

• The tertiary winding is connected in series with the primary and secondary windings to create a three-winding transformer.

• It helps in reducing voltage fluctuations and improving v...read more

Transformers are rated in kVA because it indicates the maximum amount of power that can be safely handled by the transformer.

• kVA rating is used to determine the maximum load that a transformer can handle without overheating.

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

• kVA rating helps in selecting the right size of transformer for a specific application.

• For example, a 100 kVA transformer can handle a maximum load of 100,000 volt-amperes.

• kVA ra...read more

Various protection methods are used for transformers to ensure safe operation and prevent damage.

• Overcurrent protection: Protects against excessive current flow through the transformer.

• Overload protection: Prevents the transformer from overheating due to prolonged high current.

• Differential protection: Compares the current entering and leaving the transformer to detect internal faults.

• Buchholz relay: Detects and signals the presence of gas or oil in the transformer, indicating...read more

PLC and card selection depends on the application requirements and budget.

• Identify the required inputs and outputs

• Consider the communication protocols needed

• Evaluate the processing power and memory requirements

• Determine the budget and cost of ownership

• Research and compare different brands and models

• Consider the availability of technical support and spare parts

• Ensure compatibility with existing systems

• Consider the environmental conditions of the installation site

VFD stands for Variable Frequency Drive. It is a type of motor controller that drives an electric motor by varying the frequency and voltage supplied to the motor.

• VFDs are used to control the speed and torque of AC motors in various applications.

• They work by converting fixed frequency and voltage AC power to variable frequency and voltage output.

• VFDs can improve energy efficiency, reduce wear and tear on motors, and provide precise control over motor speed.

• Example: VFDs are c...read more

Earthing design involves creating a low-resistance path for fault currents to safely dissipate into the ground.

• Determine the type of earthing system needed based on the specific requirements of the electrical installation.

• Calculate the required size of the earthing conductors based on the fault current levels and soil resistivity.

• Ensure proper bonding of all metallic structures and equipment to the earthing system to prevent dangerous potential differences.

• Regularly test and ...read more

Cable tray sizing involves considering the current carrying capacity, voltage drop, and environmental factors.

• Calculate the total current carrying capacity required for the cables in the tray.

• Consider the voltage drop limitations based on the distance and load.

• Take into account the environmental factors such as temperature, humidity, and corrosive elements.

• Select the appropriate size and material of the cable tray based on the above calculations.

• Ensure proper spacing and supp...read more

Earth loop impedance is the total impedance of the earth fault current path in an electrical circuit.

• Earth loop impedance is important for ensuring the safety of electrical installations.

• It is measured in ohms and is used to calculate the maximum fault current that could flow in the event of a fault.

• Low earth loop impedance is desirable as it helps to quickly trip circuit breakers in case of a fault.

• It is influenced by factors such as the resistance of the earth path, the imp...read more

CRI stands for Color Rendering Index, a measure of how accurately a light source illuminates colors compared to natural light.

• CRI is a scale from 0 to 100, with higher values indicating better color rendering.

• It is important in lighting design to ensure colors appear true and vibrant.

• LED lights typically have high CRI values, making them popular for applications where color accuracy is crucial.