Electrical Design Engineer Interview Questions

1). What is the relevance of the Power Factor in electric systems?

Power factor is a measurement of how efficiently electrical power is used. 

It is the ratio of actual power to apparent power. 

A high power factor suggests efficient use of electrical power, whereas a low power factor shows poor usage, resulting in larger energy losses and higher expenditures.

2). Describe the difference between a Fuse & a Circuit Breaker

Fuse	Circuit Breaker
A fuse is a one-time protection device that melts and destroys the circuit when too much current goes through it.	A circuit breaker is a reusable protective device that immediately disconnects the circuit in the event of an overload or short circuit and may be reset.

3). What is an RCD, & how does it work?

When an RCD (Residual Current Device) detects an imbalance between live & neutral currents, it disconnects the circuit to prevent electric shocks.

4). What are the different types of Earthing Systems?

Earthing systems are classified as 

• TT (Terra-Terra), 
• TN-S (Terra Neutral-Separate), 
• TN-C (Terra Neutral-Combined), 
• TN-C-S (Terra Neutral-Combined-Separate), and 
• IT (Isolated Terra).

5). How does one size a cable for a specific load?

Cable sizing is determined by several parameters, including 

• Current carrying capability, 
• Voltage drop, 
• Short-circuit rating, & 
• Environmental conditions. 

The process entails estimating the load current, selecting an appropriate cable type, and assuring compliance with applicable standards.

6). What is the role of a Transformer in an electrical system?

A transformer is used to modify the voltage levels in an electrical system, either increasing (stepping up) or decreasing (stepping down) the voltage to fit the needs of various system components.

7). What is the difference between Star & Delta connection?

Star Connection	Delta Connection
A star connection connects each phase to a common neutral point, resulting in a phase voltage equal to the line voltage divided by √3.	A delta connection connects the phases end-to-end in a loop, resulting in line voltage equal to phase voltage.

8). Define “Harmonics” in an electrical systems

Harmonics are voltage (or) current waveforms with multiples of the fundamental frequency. 

They are created by non-linear loads and can result in power quality issues such as overheating, equipment failure, and increased losses.

9). What are the benefits of adopting LED lighting over conventional lighting?

LED lighting has several advantages over traditional incandescent (or) fluorescent lighting, including higher energy efficiency, a longer lifespan, cheaper maintenance costs, rapid on/off capabilities, and superior environmental performance.

10). What is the function of a Capacitor Bank in a power system?

Capacitor banks are used to increase power factor, minimize reactive power demand, stabilize voltage levels, & reduce power system losses through reactive power compensation.

11). How do Uninterruptible Power Supply (UPS) work?

A UPS supplies backup power to crucial loads during a power loss. It consists of a battery, an inverter, and a rectifier. 

During regular operation, it charges the battery & regulates power. 

During an outage, it shifts to battery power, converting DC to AC and supplying the load.

12). What is the difference between AC & DC motors?

AC  Motor	DC Motor
AC motors are powered by alternating current & are widely utilized in applications that require continuous speed.	DC motors are powered by direct current & provide fine speed and torque control, making them ideal for applications that require variable speed.

13). What are the typical components of an electrical substation?

A typical electrical substation consists of 

• Transformers, 
• Circuit Breakers, 
• Isolators, 
• Busbars, 
• Protection Relays, 
• Instrument Transformers (CTs And VTs), and 
• Grounding Systems.

14). What is the function of a Relay in an electric circuit?

• A relay is an electrically controlled switch that controls a circuit using a low-power signal or several circuits with a single signal. 
• It isolates and protects the control circuit from the high-power load circuit.

15). Describe the difference between a single-line diagram (SLD) & a schematic diagram.

Single-Line Diagram (SLD)	Schematic Diagram
An SLD is a simplified diagram of an electrical system that depicts the major components & their connections using single lines & symbols.	A schematic diagram is a thorough representation of all connections, components, & wiring.

16). How does one do a load flow analysis in a power system?

Load flow analysis computes the voltage, current, real, & reactive power flows in a power system under steady-state conditions. 

This is accomplished utilizing approaches such as 

• Gauss-Seidel, 
• Newton-Raphson, and 
• Fast Decoupled Load Flow.

17). What is a Short Circuit Analysis, & why is it significant?

A short-circuit analysis determines the fault currents that can flow through an electrical system during a short circuit. 

It is critical to select appropriate protection measures, ensure system stability, & design equipment that can endure fault conditions.

18). What are the safety precautions to follow when working with high-voltage systems?

Safety precautions include wearing the appropriate 

• Personal Protective Equipment (PPE), 
• Lockout/Tagout Procedures, 
• Safe distances, 
• Utilizing insulated tools, and adhering to safety rules and standards.

19). What is the function of a Variable Frequency Drive (VFD) in motor control?

A VFD regulates the frequency and voltage of the electricity supplied to an AC motor, hence controlling its speed and torque. 

It enables precise motor control, energy savings, and enhanced process control.

20). How does one determine the fault level of an electrical system?

The fault level is established by calculating the potential short-circuit current at various places in the system using methods such as the impedance approach, taking into account the contributions of generators, transformers, & the network.

21). What is the function of an isolator in an electrical circuit?

An isolator is a mechanical switch that disconnects a portion of the circuit for maintenance or safety reasons. It provides physical separation, ensuring that the circuit is entirely de-energized before the work starts.

22). How do you calculate the load on a building?

To do a load calculation:

• Identify all of the building’s electrical loads, including lighting, appliances, HVAC systems, & outlets.
• Determine each load’s power rating (wattage or kilowatts).
• Sum the individual loads to determine the total power requirement.
• Use appropriate criteria for variety and safety margins.
• Ensure that the electrical supply & distribution system’s capacity equals or exceeds the entire calculated load.

23). What are the various categories of circuit protection devices?

Circuit protection devices include 

• Fuses, 
• Circuit Breakers, 
• Residual Current Devices (RCDs), 
• Ground Fault Circuit Interrupters (GFCIs), and 
• Surge Protectors. 

They prevent 

• Overcurrent, 
• Short Circuits, 
• Earth Faults, and 
• Transient Overvoltages.

24). What is the difference between Static and Dynamic Loads?

Static Loads	Dynamic Loads
A static load, such as a resistive heater, maintains its value throughout time.	A dynamic load is one that changes over time, such as motors or variable-speed drives, with varying current and power requirements.

25). What is the difference between a Breadboard and a Printed Circuit Board (PCB)

Breadboard	Printed Circuit Board (PCB)
A breadboard is a temporary prototyping platform for creating and testing electronic circuits.	A printed circuit board (PCB) is a permanent, inflexible board that has electrical channels etched into it.
It is made out of a perforated board with holes joined by metal strips, which allows for easy component insertion and removal.	Components are soldered on the PCB, making it ready for final product design & mass manufacturing.