9/9/2015 Interview Questions Electrical Engineering Tips

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Q:Difference between megger test equipment and contact resistance meter testinstruments?

A: Megger test equipment used to measure cable electric resistance, conductorcontinuity, phase identification where as contact resistance meter test instrumentsused to measure low resistance like relays ,contactors.

Q:When we connect the large capacitor bank in series ?

A :we connect large capacitor bank in series to improve the voltage power supply atthe load end in balanced transmission line when there is considerable voltage dropalong the balanced transmission line due to high impedance of the line.So in order tobring the voltage at the load terminals within its limits (i.e (+ or ­ %6 )of the rated highterminal voltage )the large capacitor bank is used in series.

Q:What is electrical diversity factor in electrical installations?

A :Electrical diversity factor is the ratio of the sum of the individual maximumdemands of the various subdivisions of a system, or part of a system, to themaximum demand of the whole system, or part of the system, under consideration.Electrical diversity factor is usually more than one.

Q:Why field rheostat is kept in minimum position while armature rheostat atmaximum position?

A :In motors at the time of starting the armature resistance is introduced to reduce thehigh starting current and the field resistance is kept minimum to have high starting torque.

Q:Why computer humming sound occurred in HT transmission line?

A :This computer humming sound is coming due to ionization (breakdown of air intocharged particles) of air around transmission conductor. This effect is called asCorona effect, and it is considered as power loss.

Q:What is rated speed?

A :At the time of motor taking normal current (rated current)the speed of the motor iscalled rated speed. It is a speed at which any system take small current and givemaximum efficiency.

Q:What is different between resistance grounding system and resistanceearthing system?

A :Resistance grounding system means connecting the neutral point of the load tothe ground to carry the residual current in case of unbalanced conditions through theneutral to the ground whereas resistance earthing system is done in an electricequipment in order to protect he equipment in occurence of fault in the system.

Q:Why should be the frequency 50 Hz 60Hz only why not others like 45, 95 56or anything , why should we maintain the frequency constant if so why it isonly 50 Hz 60Hz?

9/9/2015 Interview Questions Electrical Engineering Tips

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only 50 Hz 60Hz?

A :We can have the frequency at any frequency you like, but than you must alsomake your own motors,high voltage transformers or any other equipment you want touse.We maintain the frequency at 50hz or 60hz because the world maintains astandard at 50 /60hz and the equipments are are made to operate at thesefrequency.