Electrical Transformer Multiple choice Question (Electrical Mcqs) and Answer Part 4

              Electrical Engineering Objective Question and Answer 

                                                           Electrical Transformer MCQs with Answers

 

  

61- Which of the following protection is normally not provided on small distribution transformer? 

        

        (A)   Over current protection  

        (B) Buchholz relay  

        (C) over flux protection   

        (D) all of the above

Answer: (C)

   62- In a transformer 

        

        (A)   Open circuit test and short circuit test are conducted on low voltage side 

        (B) open circuit test and short test are conducted on high voltage side 

        (C) open circuit test is conducted on high voltage side and short circuit test on low voltage side

        (D) open circuit test is  conducted  on low voltage side and short side test on high voltage side

Answer: (D)

   63- For a transformer, operating at constant load current, maximum efficiency will occur at? 

       

         (A)   Zero power factor  

         (B) Unity power factor   

         (C) 0.8 leading power factor   

         (D)  0.8 lagging power factor

Answer: (B)

   64- The function of breather in a transformer is? 

         (A)   To provide protection against over currents  

         (B) to suppress harmonics 

         (C) to arrest flow of moisture into the tank   

         (D) To control the level of oil in the tank

Answer: (C)

   65- The efficiency of 430/200 V transformer at full load 0.8 power factor (p.f) lagging is 95%. The efficiency at full load 0.8 p.f will be  

     

        (A)   99%  

        (B) 95.5%  

        (C) 95%   

        (D) 90%

Answer: (C)

   66- A good voltage regulation of a transformer means  

        

         (A)   Difference between primary and secondary voltage is least  

         (B) difference between primary and secondary voltage is least 

         (C) output voltage fluctuation with power is the least    

         (D) output voltage fluctuation from no load to full load is least

Answer: (D)

   67- A transformer can have zero voltage regulation at 

         

        (A)   Zero power factor  

        (B) lagging power factor 

        (C) leading power factor 

        (D) unity power factor 

Answer: (C)

   68- The leakage impedances of primary and secondary windings of a transformer are (3+j4) ohms and (1+j4) ohms respectively .it can be concluded that the transformer has   

        

         (A)   Low voltage primary   

         (B) Low voltage secondary   

         (C) high voltage secondary   

         (D) less information given

Answer: (B)

   69- The color of dry silica gel is  

         (A)   Pale yellow 

         (B) pale pink 

         (C) pale green   

         (D) blue

Answer: (B)

   70- The color of moist silica gel is  

         (A)   red  

         (B) Brown  

         (C) Blue   

         (D) yellow

Answer: (C)

    71- A transformer has copper loss of 1.5% and reactance of 3.5% when tested on load. It will have better regulation at?  

         (A)   Unity power factor 

         (B) 0.8 lagging p.f  

         (C) 0.8 leading p.f  

         (D) none of it

 Answer: (A)

72- In a 50 kVA transformer the number of turns in the primary and secondary windings is 834 and 58 respectively.  If the primary is connected to 3300 volt supply, the secondary current will be

     

         (A)   15 A 

         (B) 30 A 

         (C) 218 A  

         (D) 438 A

Answer: (C)

 73- If full load copper loss of transformer is 800 W. its copper loss at 75% load will be

      

         (A)   800 W 

         (B) 450 W 

         (C) 400 W 

         (D) 200 W

 Answer: (C)

74- The essential condition for parallel operating of transformer 

      

       (A)   800 W 

       (B) 450 W
(C) 400 W 

      (D) 200 W

Answer: (C)

75- In a transformer the resistance between the primary and secondary must be

      (A)   zero 

      (B) 1kΩ 

      (C) 100kΩ 

      (D) infinite

Answer: (D)

76- The secondary of a current transformer is always short circuited under operating condition because   

     

      (A)   it avoids core saturation and high voltage induction  

      (B) it avoids high voltage surges  

      (C) it protects the primary circuit  

      (D) it is the same for operation

Answer: (A)

    77- The main advantage of an auto transformer is always short circuited under operating condition because  

       (A)   no cooling is required   

       (B) hysteresis losses are minimized  

       (C) eddy current losses are minimized  

       (D) only one winding is used as a result there is substantial saving in material

Answer: (D)

 78- Auto transformer is used

        

       (A)   zero 

       (B) 1kΩ 

       (C) 100kΩ 

       (D) infinite

Answer: (D)

79- If the break occurs in a 200:100 volt auto transformer in the winding which is common to high voltage as well as low voltage side, then the output voltage on the low voltage side will be

      

       (A)   200 V 

       (B)  150 V

       (C) 100 V 

       (D) Zero

Answer: (A)

 80- In an auto transformer, effective saving on copper and copper losses will occur, when transformer ratio is 

     (A)   More than 1 

     (B) nearly equal to 1 

     (C) less than 1 

     (D) 0.707

Answer: (B)