Mahalaxmi TMT Electrical Engineer Interview Questions and Answers

A contactor is an electrical device used for switching an electrical circuit on or off.

• Contactor is used to control the flow of electricity in a circuit.

• It consists of a coil, contacts, and an enclosure.

• When the coil is energized, the contacts close and allow current to flow.

• Contactor is commonly used in motor control applications.

• Examples of contactor include magnetic contactor and air conditioning contactor.

There are two types of transformers according to voltage transfer: step-up transformers and step-down transformers.

• Step-up transformers increase the voltage from the primary winding to the secondary winding.

• Step-down transformers decrease the voltage from the primary winding to the secondary winding.

• Step-up transformers are used in power transmission to increase voltage for long-distance transmission.

• Step-down tra...read more

The stator is used in an induction motor to generate a rotating magnetic field.

• The stator consists of a set of windings that are connected to an AC power source.

• When the AC power is applied, the stator windings create a rotating magnetic field.

• This rotating magnetic field induces currents in the rotor, which in turn creates a torque and causes the rotor to rotate.

• The stator windings are typically made of copper or...read more

MPCB and MCB are both circuit protection devices, but they differ in terms of their applications and trip characteristics.

• MCB stands for Miniature Circuit Breaker, while MPCB stands for Motor Protection Circuit Breaker.

• MCBs are primarily used for residential and commercial applications, while MPCBs are specifically designed for motor protection in industrial settings.

• MCBs have a fixed trip current rating and are t...read more

Neutral is a current-carrying conductor that completes an electrical circuit, while earth is a safety grounding conductor.

• Neutral carries current back to the source in a balanced electrical system.

• Earth is a safety measure to prevent electric shock and protect against electrical faults.

• Neutral is typically connected to the center tap of a transformer, while earth is connected to the ground.

• Neutral is part of the e...read more

ELCB stands for Earth Leakage Circuit Breaker. It is a safety device used to protect electrical circuits from electric shock.

• ELCB is designed to detect small leakage currents that may occur due to insulation failure or faulty wiring.

• When an ELCB detects a leakage current, it quickly cuts off the power supply to prevent electric shock.

• ELCBs are commonly used in homes, offices, and industries to ensure electrical sa...read more

A relay is an electrically operated switch that uses an electromagnet to mechanically control the switching action.

• Relays are commonly used in electrical systems to control high power circuits with low power signals.

• They consist of a coil, an armature, and one or more sets of contacts.

• When the coil is energized, the armature is attracted and the contacts are closed or opened, depending on the relay type.

• Relays can...read more

Transformers work on the principle of electromagnetic induction to transfer electrical energy between two or more circuits.

• Transformers consist of two or more coils of wire called windings.

• When an alternating current (AC) flows through the primary winding, it creates a changing magnetic field.

• This changing magnetic field induces a voltage in the secondary winding, which is connected to the load.

• The ratio of the nu...read more