L&T Technology Services Electrical Design Engineer Interview Questions, Process, and Tips

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

• Star delta starter is used for starting induction motors in applications where the starting current needs to be limited.

• In star delta starting, the motor is initially connected in star configuration to reduce the starting current, then switched to delta configuration for normal operation.

• This method is commonly used in industries whe...read more

Ingress protection (IP) is a rating system that defines the level of protection provided by an enclosure against intrusion of solid objects and liquids.

• IP followed by two digits (e.g. IP67) indicates the level of protection against solids and liquids respectively

• The first digit ranges from 0 to 6, with 0 offering no protection and 6 offering complete protection against dust

• The second digit ranges from 0 to 9, with 0 of...read more

MCB, MCCB, ELCB, and ACB are types of circuit breakers used for electrical protection in different applications.

• MCB (Miniature Circuit Breaker) is used for low voltage applications and has a lower breaking capacity compared to MCCB.

• MCCB (Molded Case Circuit Breaker) is used for higher voltage applications and has a higher breaking capacity compared to MCB.

• ELCB (Earth Leakage Circuit Breaker) is used to detect earth fau...read more

Cable sizing calculations involve determining the appropriate size of cables to safely carry electrical current.

• Calculate the maximum current expected to flow through the cable

• Determine the type of cable insulation and its maximum operating temperature

• Consider the voltage drop over the length of the cable

• Refer to cable sizing charts or software for guidance

• Ensure compliance with relevant standards and regulations

Relay protections are devices used to detect abnormal conditions in electrical systems and isolate them to prevent damage.

• Relay protections are used to monitor electrical parameters such as voltage, current, frequency, and phase angle.

• They are designed to trip a circuit breaker or disconnect a faulty part of the system when abnormal conditions are detected.

• Examples of relay protections include overcurrent relays, diffe...read more

Type 2 coordination is a method used in electrical engineering to ensure that a downstream circuit breaker will trip before an upstream breaker in the event of a fault.

• Type 2 coordination involves selecting circuit breakers with specific characteristics to prevent cascading trips during a fault.

• It ensures that the downstream breaker will trip first to isolate the fault, protecting the upstream breaker and preventing un...read more

MCC panel stands for Motor Control Center panel. Types of starters include DOL, star-delta, and soft starter.

• MCC panel is a type of electrical control panel that houses motor starters, drives, and other control equipment.

• Types of starters include Direct-On-Line (DOL), Star-Delta, and Soft Starter.

• DOL starter provides full voltage to the motor upon start, while star-delta starter reduces the voltage during start to mini...read more