Electrical interview questions

Electrical interview questions:

Electrical interview questions:Different between megger and contact resistance meter? 

Answers:Megger used to measure cable resistance, conductor continuity, phase identification where as contact resistance meter used to measure low resistance like relays ,contactors.

Electrical interview questions :When we connect the capacitor bank in series ?

Answers:we connect capacitor bank in series to improve the voltage profile at the load end in transmission line there is considerable voltage drop along the transmission line due to impedance of the line. so in order to bring the voltage at the load terminals within its limits i.e (+ or - %6 )of the
rated terminal voltage the capacitor bank is used in series

Electrical interview questions:What is Diversity factor in electrical installations?
Answers:Diversity factor is the ratio of the sum of the individual maximum demands of the various subdivisions of a system, or part of a system, to the maximum demand of the whole system, or part of the system, under consideration. Diversity factor is usually more than one.

Electrical interview questions:Why field rheostat is kept in minimum position while armature rheostat at maximum position?
Answers:In motors at the time of starting the armature resistance is introduced to reduce the high starting current and the field resistance is kept minimum to have high starting
torque.

Electrical interview questions:Why humming sound occurred in h HT transmission line?
Answers:This sound is coming due to ionization (breakdown of air into charged particles) of air around transmission conductor. This effect is called as Corona effect, and it is considered as power loss.

Electrical interview questions :what is rated speed?

Answers:At the time of motor taking normal current (rated current)the speed of the motor is called rated speed. It is a speed at which any system take small current and give maximum efficiency.

Electrical interview questions:What is different between grounding and earthings?

Answers:Grounding means connecting the neutral point of the load to the ground to carry the residual current in case of unbalanced conditions through the neutral to the ground whereas earthing is done in an electric equipment in order to protect he equipment in occurence of fault in the system.

Electrical interview questions:Why should be the frequency is 50 hz only why not others like 45, 95 56 or anything , why should we maintain the frequency constant if so why it is only 50 ?

Answers:We can have the frequency at any frequency you like, but than you must also make your own motors, transformers or any other equipment you want to use.We maintain the frequency at 50hz or 60hz cos the world maintains a standard at 50 /60hz and the equipments are are made to operate at these frequency.