DEC Infra Electrician Interview Questions and Answers

A transformer is an electrical device that transfers electrical energy between two or more circuits through electromagnetic induction.

• Transformers are used to increase or decrease the voltage of an alternating current (AC) power supply.

• They consist of two coils of wire, called the primary and secondary, wrapped around a magnetic core.

• When an AC current flows through the primary coil, it creates a magnetic field that in...read more

Earthing is the process of connecting electrical equipment to the earth to prevent electric shock.

• There are several types of earthing, including plate earthing, rod earthing, pipe earthing, and strip earthing.

• Plate earthing involves burying a copper plate in the earth and connecting it to the electrical equipment.

• Rod earthing involves driving a copper rod into the earth and connecting it to the electrical equipment.

• Pip...read more

Circuit breakers are of different types such as thermal, magnetic, hydraulic-magnetic, and residual current devices.

• Thermal circuit breakers use a bimetallic strip to trip the breaker when it gets too hot.

• Magnetic circuit breakers use an electromagnet to trip the breaker when it detects an overload.

• Hydraulic-magnetic circuit breakers combine the features of both thermal and magnetic circuit breakers.

• Residual current de...read more

Star delta starter is an electrical motor starting mechanism that reduces the starting current and torque.

• Used for starting high power motors

• Consists of three contactors and a timer

• Initially starts the motor in star configuration and then switches to delta configuration

• Reduces starting current and torque

• Commonly used in industrial applications

Buchholz relay is a protective device used in oil-filled transformers to detect and prevent faults.

• It is a type of gas actuated relay

• It is installed in the oil-filled transformer tank

• It detects the presence of gas or air bubbles in the oil

• It trips the transformer if a fault is detected

• It helps to prevent major damage to the transformer