EXL Service Interview Questions and Answers

Neutral is grounded in star connected transformer for safety and to limit voltage rise.

• Grounding neutral limits voltage rise in case of unbalanced loads.

• It provides a path for fault current to flow, which helps in detecting and isolating faults.

• It reduces the risk of electric shock to personnel and damage to equipment.

• In some countries, it is a legal requirement to ground the neutral in electrical systems.

• Example: In a 3-phase, 4-wire system, the neutral is grounded to limit ...read more

In Star connection, line voltage is equal to the square root of 3 times phase voltage.

• Line voltage is the voltage between any two line conductors in a three-phase system.

• Phase voltage is the voltage between any line conductor and the neutral point in a three-phase system.

• In a Star connection, all three phases are connected to a common neutral point.

• The relationship between line voltage and phase voltage in Star connection is given by the formula: Line voltage = √3 x Phase vol...read more

Transformer losses refer to the energy dissipated in a transformer during its operation.

• Transformer losses include copper losses and iron losses.

• Copper losses occur due to the resistance of the transformer windings.

• Iron losses, also known as core losses, occur due to hysteresis and eddy currents in the transformer core.

• Copper losses can be minimized by using larger conductor sizes and reducing the resistance of windings.

• Iron losses can be reduced by using high-quality magneti...read more

CT and PT are connected in circuit to measure current and voltage respectively.

• CT is connected in series with the load to measure current

• PT is connected in parallel with the load to measure voltage

• CT and PT are used together to measure power in a circuit

• The ratio of CT and PT is important for accurate measurement

Solar PV modules convert sunlight into electricity using photovoltaic effect.

• Solar PV modules consist of multiple solar cells connected in series and parallel.

• Each solar cell is made of semiconductor material, usually silicon.

• When sunlight hits the solar cell, it excites the electrons in the semiconductor material, creating a flow of electricity.

• The electricity generated by the solar cells is direct current (DC), which is then converted to alternating current (AC) using an in...read more

Power is the rate at which energy is transferred, while energy is the ability to do work.

• Power is measured in watts, while energy is measured in joules.

• Power is the rate at which energy is used or transferred, while energy is the capacity to do work.

• A light bulb may have a power rating of 60 watts, but the energy it consumes over time is measured in watt-hours.

• Energy can exist in different forms, such as kinetic, potential, thermal, and chemical energy.

• Power can be calculated...read more

IGBT stands for Insulated Gate Bipolar Transistor, a power semiconductor device used for switching and amplification of electrical power.

• IGBT is a three-terminal device with a collector, emitter, and gate.

• It combines the advantages of MOSFET and BJT transistors.

• It is commonly used in high power applications such as motor drives, power supplies, and renewable energy systems.

• IGBTs have low on-state voltage drop and high switching speed.

• Examples of IGBTs include Mitsubishi IGBT ...read more