100+ Junior Engineer Electrical Interview Questions and Answers

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

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

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

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

Thyristor speed control offers precise control, energy efficiency, and reduced maintenance costs.

• Precise control of motor speed

• Improved energy efficiency by reducing power wastage

• Reduced maintenance costs due to less wear and tear on motor components

• Smooth acceleration and deceleration of motors

• Ability to control large motors with ease

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.

Yes, I can draw the control diagram of Star Delta Starter.

• The diagram consists of three contactors, a timer, and an overload relay.

• In the starting position, the contactors are in the open position.

• When the start button is pressed, the timer starts and the contactors close in a specific sequence.

• After a set time, the contactors switch to the delta position.

• The overload relay protects the motor from overloading.

• The control circuit is wired separately from the power circuit.

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

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

Parameters for setting Variable Voltage and Frequency Drives (VVFD) include voltage, frequency, acceleration time, deceleration time, and motor overload protection.

• Voltage setting determines the output voltage supplied to the motor.

• Frequency setting controls the speed of the motor.

• Acceleration time sets the time taken for the motor to reach full speed from standstill.

• Deceleration time determines how quickly the motor slows down.

• Motor overload protection is important to preven...read more

Setting up a multiple function relay involves configuring the relay settings, connecting it to the power source and load, and testing its functionality.

• Configure the relay settings based on the specific functions required, such as overcurrent protection, voltage monitoring, or phase sequence detection.

• Connect the relay to the power source and load using appropriate wiring and terminals.

• Test the relay's functionality by simulating different fault conditions and verifying that ...read more

I have worked with Allen-Bradley PLCs and have experience with inter-node communication.

• I have experience working with Allen-Bradley PLCs, specifically the ControlLogix series.

• Inter-node communication refers to the exchange of data between different nodes or devices within a PLC network.

• This communication can be achieved using various protocols such as Ethernet/IP, DeviceNet, or ControlNet.

• Examples of inter-node communication include sending data between PLCs in a production ...read more

I believe integrating new technologies like energy storage systems and smart inverters into solar installations is crucial for maximizing efficiency and sustainability.

• Energy storage systems can help store excess energy generated by solar panels for use during periods of low sunlight or high demand.

• Smart inverters can optimize the performance of solar installations by adjusting voltage and frequency levels to match grid requirements.

• Experience with these technologies can incl...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

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

Questions asked in a Junior Engineer Electrical interview

• Types of sensors include temperature, pressure, proximity, and motion sensors

• Types of drives include AC drives, DC drives, and servo drives

• DOL, STAR-DELTA, and FORWARD-REVERSE are types of motor starters

• Other types of starters include soft starters and auto-transformer starters

• Critical situation faced in previous company: power outage during a major production run

• Maximum questions asked from resume

Regular maintenance of electrical equipment ensures safety, efficiency, and longevity through systematic inspections and repairs.

• Conduct regular inspections to identify wear and tear, e.g., checking for frayed wires.

• Clean equipment to prevent dust accumulation, which can cause overheating.

• Test and calibrate equipment periodically, such as measuring voltage and current levels.

• Replace worn-out parts promptly, like circuit breakers or fuses.

• Document maintenance activities for fu...read more

Maintenance procedures for an OLTC transformer involve regular inspection, cleaning, lubrication, and testing.

• Regularly inspect the OLTC for any signs of wear, damage, or overheating.

• Clean the OLTC contacts and components to ensure proper functioning.

• Lubricate moving parts to prevent friction and wear.

• Perform routine testing to check the OLTC's operation and efficiency.

• Keep detailed records of maintenance activities and any issues encountered.

• Consult manufacturer guidelines f...read more

A Buchholz relay detects gas and oil flow changes in transformers, providing protection against faults.

• Monitors gas accumulation due to insulation failure or overheating.

• Detects sudden oil movement caused by internal faults.

• Provides alarm signals for maintenance or immediate action.

• Commonly used in oil-immersed transformers.

• Example: If a transformer overheats, gas is produced, triggering the relay.

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.

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

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