Oman National Engineering & Investment Company Electrical Technician Interview Questions and Answers

Single phase and three phase are two types of electrical power distribution systems.

• Single phase has one live conductor and one neutral conductor, while three phase has three live conductors and one neutral conductor.

• Single phase is commonly used in residential and small commercial applications, while three phase is used in industrial and large commercial applications.

• Single phase power supply is suitable for low power...read more

R, Y, B phases are the three phases of AC power supply. They differ in their phase angle and voltage level.

• R phase has a phase angle of 0 degrees and is usually connected to the red wire.

• Y phase has a phase angle of 120 degrees and is usually connected to the yellow wire.

• B phase has a phase angle of 240 degrees and is usually connected to the blue wire.

• The voltage level of each phase is the same, but they are out of ph...read more

In series, voltage adds up while current remains the same. In parallel, voltage remains the same while current adds up.

• In series, batteries are connected end-to-end, positive to negative. In parallel, batteries are connected positive to positive and negative to negative.

• Series connection increases voltage but does not increase current. Parallel connection increases current but does not increase voltage.

• Series connectio...read more

Periodic maintenance of batteries is crucial for their longevity and optimal performance.

• Check the battery terminals for corrosion and clean them if necessary

• Inspect the battery case for any cracks or damage

• Ensure that the battery is securely fastened in place

• Check the electrolyte level and top up with distilled water if required

• Test the battery voltage and recharge if necessary

A faulty battery can be identified by checking its voltage, capacity, and physical appearance.

• Check the voltage of the battery using a multimeter

• Test the capacity of the battery using a battery tester

• Inspect the physical appearance of the battery for any signs of damage or leakage

• Check the battery terminals for corrosion or loose connections

• Compare the battery's performance to its specifications

FUSE, MCB, ELCB, and RCCB are all electrical protection devices, but they differ in their functions and applications.

• FUSE is a simple device that protects electrical circuits from overloading or short-circuiting by melting and breaking the circuit.

• MCB (Miniature Circuit Breaker) is an automatic switch that trips and cuts off the power supply when there is an overload or short-circuit.

• ELCB (Earth Leakage Circuit Breaker...read more

A DOL starter is a direct online motor starter that provides full voltage to the motor.

• Consists of a contactor, overload relay, and start/stop buttons

• The contactor connects the motor to the power supply

• The overload relay protects the motor from overloading

• The start/stop buttons control the on/off function of the motor

• Used for small motors with low starting current

• Not suitable for large motors or motors with high starti