90+ Assistant Electrical Engineer Interview Questions and Answers

Planning and executing a 1 KM 11KV transmission line requires careful consideration of various factors.

• Conduct a site survey to determine the route and identify any obstacles

• Design the transmission line based on the load requirements and voltage drop calculations

• Obtain necessary permits and approvals from local authorities

• Procure materials and equipment required for construction

• Ensure safety measures are in place during construction

• Test and commission the transmission line be...read more

To communicate between multiple Mitsubishi PLCs, use the ladder programming language and establish a network connection.

• Use the GX Works2 software to program the Mitsubishi PLCs

• Configure the network settings on each PLC to establish a network connection

• Assign unique IP addresses to each PLC

• Use the Ethernet communication protocol to exchange data between PLCs

• Implement ladder logic instructions to send and receive data between PLCs

• Use communication modules or special function b...read more

IMCC panels are used for motor control and automation. 800A MCC panel requires specific switchgear and has a fault level in the busbars.

• IMCC panels are used for motor control and automation in industrial settings

• 800A MCC panel requires specific switchgear such as circuit breakers and fuses

• The fault level for 800A MCC panel in the busbars depends on the system voltage and impedance

• PLC and automation systems are used to control and monitor the IMCC panels

• PLC programming involve...read more

The installation process for a 100 KVA DTR involves site preparation, foundation construction, equipment placement, wiring, and testing.

• Prepare the site by clearing the area and ensuring proper drainage

• Construct a foundation that is level and able to support the weight of the DTR

• Place the DTR on the foundation and secure it in place

• Connect the wiring according to the manufacturer's instructions

• Test the DTR to ensure it is functioning properly

The Megger value of unsatisfactory insulation can be improved by drying out the insulation, repairing any damaged areas, and retesting.

• Dry out the insulation using heaters or fans to remove moisture

• Repair any damaged areas by replacing or patching up the insulation

• Retest the insulation using the Megger to ensure the value has improved

• Consider using insulation coatings or sealants to improve the insulation resistance

Common malfunctions and troubleshooting methods for electrical feeders

• Common malfunctions include short circuits, overloads, and open circuits

• Troubleshooting methods involve checking for loose connections, using a multimeter to test for continuity, and inspecting for physical damage

• In case of a short circuit, isolate the fault by disconnecting sections of the feeder until the fault is located

• For overloads, check the load distribution and consider redistributing the load or up...read more

Safety devices used in conveyor belts include pull cord switches, belt sway switches, and emergency stop switches.

• Pull cord switches are used to stop the conveyor belt in case of emergency by pulling the cord.

• Belt sway switches are used to detect any misalignment or deviation of the belt and trigger an alarm or stop the conveyor.

• Emergency stop switches are placed at regular intervals along the conveyor belt to quickly stop the operation in case of emergency.

The minimum megger value required for high tension (HT) and low tension (LT) motors is typically 500V for HT motors and 250V for LT motors.

• Minimum megger value for HT motors is usually 500V

• Minimum megger value for LT motors is typically 250V

• Megger testing is essential to ensure insulation resistance in motors

Steps to be taken if a transformer trips due to Buchholz relay acting

• Immediately isolate the transformer from the system to prevent further damage

• Inspect the transformer and Buchholz relay for any faults or leaks

• Reset the Buchholz relay and check for proper functioning

• Investigate the cause of the trip such as internal faults or oil contamination

• Repair or replace any faulty components before re-energizing the transformer

Variable frequency drives (VFDs) are used in ID fan motor and cooler motor.

• VFDs are used to control the speed of the motor and save energy.

• ID fan motor and cooler motor require different speeds at different times, which can be achieved through VFDs.

• VFDs can also protect the motor from damage due to overvoltage or undervoltage.

• Examples of VFDs include ABB ACS880, Siemens Sinamics G120, and Schneider Electric Altivar Process ATV600.

Operation and maintenance procedures for transformer feeders and motor feeders involve regular inspections, testing, and preventive maintenance to ensure optimal performance and safety.

• Regularly inspect transformer and motor feeders for signs of wear, damage, or overheating.

• Perform routine testing to check for proper voltage levels, insulation resistance, and overall functionality.

• Conduct preventive maintenance such as cleaning, tightening connections, and replacing worn-out ...read more

Earthing procedure for a distributor transformer involves connecting the transformer to a grounding system.

• The transformer should be connected to a grounding system using a grounding electrode.

• The grounding electrode should be buried in the earth at a depth of at least 2.5 meters.

• The grounding electrode should be made of copper or galvanized iron.

• The grounding system should have a resistance of less than 1 ohm.

• The earthing procedure should be carried out by a qualified electr...read more

PPE stands for Personal Protective Equipment. Building a safety work culture involves training, communication, enforcement, and leading by example.

• PPE includes items like helmets, gloves, goggles, and safety shoes to protect workers from hazards.

• Conduct regular safety training sessions to educate employees on the importance of using PPE.

• Communicate safety protocols clearly and consistently to all employees.

• Enforce safety policies and procedures to ensure compliance.

• Lead by ex...read more

Transformers breathe through cooling systems and use materials like oil or air for insulation.

• Transformers have cooling systems to dissipate heat generated during operation.

• The cooling system can be either oil-based or air-based.

• Oil-filled transformers use oil as a cooling and insulating medium.

• Air-cooled transformers use fans or radiators to cool the windings.

• The cooling system ensures the transformer operates within safe temperature limits.

PF is power factor, a measure of how efficiently electrical power is being used. A capacitor is an electrical component that stores energy. A capacitor bank is a group of capacitors connected together to improve power factor.

• Power factor (PF) is the ratio of real power to apparent power in an AC circuit.

• A capacitor is an electrical component that stores energy in an electric field.

• A capacitor bank is a group of capacitors connected together to improve power factor by reducing...read more

Electrical preventive maintenance activities include inspection, testing, cleaning, and replacement of components to prevent breakdowns.

• Regular inspection of electrical systems

• Testing of equipment for proper functioning

• Cleaning of electrical components to prevent dust buildup

• Replacement of worn out or damaged parts

• Tightening of connections to prevent loose connections

• Checking for overheating issues

• Updating software/firmware as needed

• Implementing safety measures to prevent acc...read more

Maintenance practices for transformers include regular inspections, testing, cleaning, and oil analysis.

• Regularly inspecting for signs of overheating, leaks, or damage

• Performing routine testing such as insulation resistance and turns ratio tests

• Keeping the transformer and surrounding area clean and free of debris

• Conducting oil analysis to monitor the condition of the transformer oil

• Ensuring proper ventilation and cooling of the transformer

• Checking and tightening connections a...read more

Protective measures for a transformer include overcurrent protection, temperature monitoring, and regular maintenance.

• Overcurrent protection: Use fuses or circuit breakers to protect against excessive current flow.

• Temperature monitoring: Install temperature sensors to prevent overheating.

• Regular maintenance: Inspect and test the transformer regularly to ensure proper functioning.

• Grounding: Properly ground the transformer to prevent electrical shocks and damage.

• Oil level monit...read more

The control circuit of a star-delta starter involves two contactors and a timer for smooth transition from star to delta connection.

• The control circuit includes a main contactor for connecting the motor in star during starting.

• A timer is used to delay the transition from star to delta connection to prevent sudden voltage spikes.

• Once the timer elapses, a delta contactor is energized to switch the motor windings from star to delta configuration.

• This control circuit ensures a sm...read more

Motors convert electrical energy into mechanical energy, while generators convert mechanical energy into electrical energy.

• Motors work on the principle of electromagnetic induction, where a current-carrying conductor experiences a force in a magnetic field.

• Generators work on the principle of Faraday's law of electromagnetic induction, where a changing magnetic field induces an electromotive force in a conductor.

• Motors and generators both involve the interaction between magnet...read more

Voltage regulation is the process of maintaining a stable voltage level at the distribution level.

• Voltage regulation is achieved by using transformers and voltage regulators to adjust the voltage as needed.

• Voltage regulators can be either tap-changing transformers or electronic devices that adjust the voltage automatically.

• By monitoring the voltage levels and making adjustments as necessary, the desired voltage is maintained at the distribution level.

• Voltage regulation is imp...read more

A transformer is an electrical device that transfers electrical energy from one circuit to another through electromagnetic induction.

• Transformers work on the principle of electromagnetic induction

• They have two coils, primary and secondary, wound around a common magnetic core

• When an alternating current flows through the primary coil, it creates a magnetic field which induces a voltage in the secondary coil

• The voltage in the secondary coil is proportional to the number of turns...read more

Power factor (Pf) is a measure of how effectively electrical power is being used. It can be controlled using various methods.

• Power factor (Pf) is the ratio of real power (kW) to apparent power (kVA) in an electrical system.

• A low power factor indicates inefficient use of electrical power, leading to increased energy costs and potential equipment damage.

• Power factor can be improved by adding power factor correction capacitors to the electrical system.

• Other methods to control po...read more

Different types of Earthings include: protective earthing, functional earthing, system earthing, and lightning earthing.

• Protective earthing is used to prevent electric shock and ensure safety.

• Functional earthing is used to provide a reference potential for electrical equipment.

• System earthing is used to stabilize voltage levels and protect against faults.

• Lightning earthing is used to protect structures from lightning strikes.

• Other types of earthing include signal earthing, in...read more

The size of cable used for a 1 ton AC depends on various factors such as voltage, current, and distance.

• The cable size is determined by the current rating of the AC unit.

• For a 1 ton AC, the current rating is typically around 5-7 amps.

• The cable size can be calculated using the current carrying capacity of the cable and the voltage drop considerations.

• Factors like the distance between the AC unit and the power source also play a role in determining the cable size.

• Consulting ele...read more

A servo motor is a rotary actuator that allows for precise control of angular position.

• Servo motors are commonly used in robotics, automation, and control systems.

• They consist of a DC motor, a position feedback sensor, and a control circuit.

• The control circuit receives a control signal and adjusts the motor's position accordingly.

• Servo motors can rotate between 0 and 180 degrees, or even continuously in some cases.

• They provide high torque and accurate positioning.

• Modes of com...read more

Transformer oil should be tested for dielectric strength, acidity, water content, and dissolved gas analysis. Significant out gases include methane, ethylene, and acetylene.

• Dielectric strength test measures the ability of the oil to withstand electric stress without breaking down.

• Acidity test determines the level of acidic compounds present in the oil, which can degrade insulation.

• Water content test checks for moisture that can reduce the dielectric strength of the oil.

• Dissol...read more

A transformer works 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, which are wound around a core made of ferromagnetic material.

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

• This changing magnetic field induces a voltage in the secondary coil through electromagnetic induction...read more

Low forward power in a generator refers to the situation where the power output of the generator is lower than expected or required.

• Low forward power can be caused by issues such as mechanical problems, fuel supply issues, or electrical faults.

• It can result in reduced efficiency, poor performance, and potential damage to the generator.

• Regular maintenance and monitoring can help prevent and address low forward power issues.

• For example, a generator may experience low forward po...read more

Motor working principles involve the interaction between magnetic fields and electric currents to produce rotational motion.

• Electric current is passed through a coil of wire, creating a magnetic field that interacts with the magnetic field of a permanent magnet to produce rotational force.

• The direction of the current determines the direction of the rotation.

• Motor testing involves measuring the motor's performance characteristics such as speed, torque, and efficiency.

• Testing c...read more

UPS stands for Uninterruptible Power Supply. The maximum capacity of UPS varies depending on the model and brand.

• UPS stands for Uninterruptible Power Supply

• Maximum capacity of UPS varies depending on model and brand

• Common capacities range from 350VA to 10kVA

• Example: APC Smart-UPS 1500VA has a capacity of 1500VA

Distribution transformers are typically installed in rectangular areas near the load centers for efficient power distribution.

• Distribution transformers are installed in rectangular areas near load centers to step down voltage for distribution to consumers.

• They are usually placed outdoors on concrete pads or inside fenced enclosures for safety and accessibility.

• The location should allow for easy maintenance and access for utility workers.

• Examples of where distribution transfor...read more

Machines ratings are in kVA instead of kW due to the presence of reactive power.

• kVA represents the apparent power of a machine, which includes both real power (kW) and reactive power (kVAR).

• Reactive power is required by machines with inductive or capacitive loads to create magnetic fields or store energy.

• kW represents the actual power consumed or produced by a machine, while kVA represents the total power required to perform work.

• Using kVA ratings helps in sizing electrical e...read more

The size of cable is selected based on factors like current carrying capacity, voltage drop, and environmental conditions.

• Consider the current carrying capacity of the cable, which depends on the load and the type of cable.

• Calculate the voltage drop to ensure it is within acceptable limits.

• Take into account the environmental conditions such as temperature, moisture, and chemical exposure.

• Refer to relevant standards and codes for guidance on cable sizing.

• Consider future expans...read more

Sensors include temperature, pressure, proximity, light, and motion sensors. Timers include programmable, countdown, and interval timers.

• Temperature sensors measure the temperature of an object or environment

• Pressure sensors measure the pressure of a fluid or gas

• Proximity sensors detect the presence of nearby objects

• Light sensors measure the intensity of light

• Motion sensors detect movement

• Programmable timers can be set to turn on or off at specific times

• Countdown timers count...read more

A soft starter is a device used to gradually start and control the speed of an electric motor.

• Soft starters are used to reduce the mechanical stress on motors during startup.

• They provide a gradual increase in voltage to the motor, preventing sudden surges.

• Soft starters can also control the acceleration and deceleration of the motor.

• They are commonly used in applications where a smooth and controlled startup is required, such as conveyor belts or pumps.

• Example: A soft starter ...read more

Parameters for synchronisation of DG set to bus bar

• Frequency matching between DG set and bus bar

• Voltage matching between DG set and bus bar

• Phase sequence matching between DG set and bus bar

• Synchronisation panel settings

• Proper earthing and grounding

• Load sharing and load transfer

• Protection and safety measures

RTD and TC are used for temperature measurement in various industries.

• RTD stands for Resistance Temperature Detector and TC stands for Thermocouple.

• RTD measures temperature by sensing the change in resistance of a metal wire as temperature changes.

• TC measures temperature by sensing the voltage generated by the junction of two dissimilar metals.

• RTD is more accurate and stable than TC, but TC is more rugged and can measure higher temperatures.

• RTD is commonly used in industries ...read more

Bus changeover scheme is a system used to transfer power supply from one source to another in case of a fault or maintenance.

• Bus changeover scheme involves the use of automatic transfer switches (ATS) or manual switches to transfer power sources.

• It ensures uninterrupted power supply by quickly switching to an alternate power source when needed.

• Common examples include dual power supply systems in data centers or hospitals.

• The scheme is designed to prevent power outages and min...read more

The generator excitation system is a system that provides the necessary field current to the generator rotor to produce the desired voltage output.

• The excitation system controls the magnetic field strength of the generator to regulate the output voltage.

• It typically consists of an exciter, voltage regulator, and automatic voltage regulator (AVR).

• The exciter produces the field current, the voltage regulator adjusts the excitation level based on load changes, and the AVR mainta...read more

Single phase machines are designed by using a single phase power supply and incorporating specific design elements.

• Single phase machines use a single phase power supply, typically from a residential or commercial electrical system.

• They are designed with specific components such as a single phase winding, a capacitor for starting, and a centrifugal switch for switching between starting and running modes.

• Examples of single phase machines include single phase induction motors, s...read more

HG fuse is a high-grade fuse used in electrical systems to protect against overcurrents.

• HG fuse stands for High-Grade fuse.

• It is used in electrical systems to protect against overcurrents.

• It works by melting a fuse element when excessive current flows through it.

• The melting of the fuse element breaks the circuit and prevents damage to the electrical system.

• HG fuses are commonly used in industrial applications and power distribution systems.

My favorite subject in engineering is power systems.

• I enjoy learning about the generation, transmission, and distribution of electrical power.

• I find it fascinating how power systems are designed to ensure reliable and efficient delivery of electricity.

• I am particularly interested in renewable energy sources and their integration into power systems.

• I have taken courses in power systems analysis, power electronics, and renewable energy systems.

• I have also completed projects rel...read more

Earthing is a process of connecting electrical equipment to the ground to prevent electric shock and protect against electrical faults.

• Earthing is done by connecting the electrical equipment to a conductive material, such as a metal rod, buried in the ground.

• The purpose of earthing is to provide a path for the flow of excess electrical current to the ground, preventing damage to the equipment and ensuring safety.

• Earthing helps in dissipating static electricity and reducing el...read more

Line capacitance in transmission lines provides several advantages.

• Improves power factor by compensating for inductive reactance

• Reduces voltage drop and improves voltage regulation

• Enhances stability and reduces the risk of voltage collapse

• Enables efficient power transfer over long distances

• Helps in reducing electromagnetic interference (EMI)

• Allows for the use of higher transmission voltages

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.

• VFD controls the speed and torque of an AC motor by varying the frequency of the electrical supply to the motor.

• It converts fixed frequency and voltage AC power to variable frequency and voltage output.

• VFDs are commonly used in HVAC systems, pumps, conveyors, and other industrial applications.

• The working principle i...read more

RTD stands for Resistance Temperature Detector, used to measure temperature. Types of motors used in automation machinery include DC motors, AC motors, and stepper motors.

• RTD stands for Resistance Temperature Detector, used to measure temperature accurately

• Types of motors used in automation machinery include DC motors, AC motors, and stepper motors

• DC motors are commonly used for variable speed applications

• AC motors are used for constant speed applications

• Stepper motors are us...read more