JLL Interview Questions and Answers

Electromechanical relays are commonly used in transformers for protection and control purposes.

• Electromechanical relays are commonly used in transformer protection schemes to detect faults and isolate the transformer from the system.

• Different types of relays used in transformers include overcurrent relays, differential relays, and distance relays.

• Solid-state relays are also gaining popularity due to their faster response times and higher reliability.

• Examples of relay manufact...read more

Transformer rating in kVA is used instead of kW due to the presence of reactive power.

• kVA takes into account both active power (kW) and reactive power, providing a more accurate representation of the transformer's capacity.

• Reactive power is necessary for the magnetic field in transformers and does not perform useful work like active power.

• Using kVA allows for better sizing and selection of transformers to handle both active and reactive power components.

• For example, a transfo...read more

Selection of components involves considering factors like functionality, durability, cost, and compatibility.

• Identify the specific requirements of the system or equipment

• Research and compare different options based on factors like quality, price, and availability

• Consider the compatibility of components with existing systems

• Evaluate the durability and maintenance requirements of each component

• Ensure that the selected components meet safety and regulatory standards

PLC stands for Programmable Logic Controller, which is a digital computer used for automation of electromechanical processes.

• PLC is used to control machinery in manufacturing processes.

• It uses a programmable memory to store instructions and specific functions.

• PLCs are commonly used in industries like automotive, food processing, and packaging.

• They can be programmed using ladder logic, function block diagrams, or structured text.

• PLCs help in improving efficiency, reducing down...read more

The amperage of a 10 hp motor depends on the voltage it operates at.

• The amperage can be calculated using the formula: Amps = (Horsepower x 746) / Voltage

• For example, if the voltage is 220V, the amperage would be (10 x 746) / 220 = 33.8 Amps

• The amperage may vary depending on the efficiency and power factor of the motor

Power calculation involves converting between different units of power.

• Power can be calculated using the formula P = IV, where P is power, I is current, and V is voltage.

• Common units of power include watts (W), kilowatts (kW), and horsepower (hp).

• To convert between units, use conversion factors. For example, 1 horsepower is equal to approximately 0.7457 kilowatts.

• Power calculations are important in various fields such as electrical engineering, physics, and mechanical enginee...read more

Star delta starter is used to reduce the starting current of induction motors.

• Reduces the starting current of induction motors

• Prevents excessive voltage drop in the power supply

• Protects the motor from overheating

• Increases the lifespan of the motor

• Commonly used in applications where the motor needs to start under load

• Example: Used in industries for large motors like pumps, compressors, and fans

Material properties refer to the characteristics of a material that determine how it will behave under certain conditions.

• Material properties include strength, hardness, elasticity, density, and thermal conductivity.

• Different materials have different properties that make them suitable for specific applications. For example, steel is known for its high strength and durability, making it ideal for construction.

• Understanding material properties is crucial for selecting the right...read more