Electrical Transformer Multiple choice Question (Electrical Mcqs) and Answer Part 8

        Electrical Engineering Objective Question and Answer 


  





141- The power factor at which the regulation will be maximum is? 


        (A) 0.385 leading

        (B) 0.615 leading 

        (C) 0.385 lagging  

        (D) 0.615 lagging 

        Answer: (C)

       142- The maximum of this transformer will be ? 

        (A) 0.5%

        (B) 2.5%

        (C) 4.5%

        (D) 6.5% 

        Answer: (D)

       143- A 480/120 V . 5 k VA two winding transformer is to be used as an auto transformer to supply power at 480 V from 600 V source. The k VA capacity as auto transformer will be  

        (A) 10 k VA

        (B) 15 k VA 

        (C) 20 k VA

        (D) 25 k VA

        Answer: (D)

       A  3-phase step down transformer is connected to 6.6 kV mains and takes 10 A. The ratio of turns per phase is 12 and losses may be neglected (Q 144-147) 
       
       144- The secondary line voltage will be least for which of the following connections?

        (A) Delta-delta

        (B) star-star 

        (C) Delta-delta

        (D) star-star 

        Answer: (D)

      145- The secondary line voltage  will be identical for which of the following two connections?

        (A) Δ/Δ and Y/Y 

        (B) Y/Δ and Δ/Y

        (C) Y/Y and Δ/Y

        (D) Δ/Y and Δ/Δ

        Answer: (A)

       146- The secondary line current will be maximum for which of the following connections?

        (A) Delta-delta

        (B) Delta-star 

        (C) Star-star

        (D) Star-delta

         Answer: (B)

        147- The secondary line current will be maximum for which of the following connections?

        (A) Delta-delta

        (B) Delta-delta

        (C) Star-star

        (D) Star-delta

          Answer: (D)

        148- Three 1100/110 V transformers connected. delta/delta supplying a lightning load of 100 kW , what current in secondary will be flowing in each transformer?

        (A) 303 A

        (B) 255 A

        (C) 203 A

        (D) 153 A

         Answer: (A)

       149- Two single phase transformers with equal turns have impedance of ( 0.5 + j 0.3 ) ohms and ( 0.6 + j 10 ) ohms with respect to the secondary. if they operate in parallel , how they will share a load of 100 kW at 0.8 p.f. lagging?

        (A) 50 kW , 50 kW

        (B) 62 kW , 38kW

        (C) 78.2 kW , 21.8 kW

        (D) 85.5 kW , 14.5 kW

         Answer: (C)

       A load of 800 kW at 0.8 lagging p.f. is supplied by two 3 phase transformers rated 400 kVA and 600 kVA operating in parallel. The transformer have the same turn ratio and their per unit resistance and reactance are given as (Q 150-154)
                                               resistance        reactances 
       400 kVA transformer      0.02                  0.04
       600 kVA transformer      0.01                  0.05
       
       150- The load shared 400 kVA transformer will be 

        (A) 234 kVA

        (B) 325 kVA

        (C) 456 kVA

        (D) 525 kVA

         Answer: (C)

       151- The load shared by 600 k VA transformer will be 

        (A) 546 k VA

        (B) 456 k VA

        (C) 412 k VA

        (D)388 k VA

          Answer: (A)

       152- Power factor of 600 k VA transformer will be

        (A) 0.882 lagging 

        (B) 0.725 lagging 

        (C) 0.625 leading 

        (D) 0.182 leading 

         Answer: (A)

       153- Power factor of 600 k VA transformer will be 

        (A) 0.882 lagging 

        (B) 0.725 lagging 

        (C) 0.625 leading 

        (D)  0.182 leading

         Answer: (B)

      154- The percentage regulation of 4800/240 volt distribution transformer is 3.33 percent. The voltage to which the secondary voltage will rise when full load is removed , will be

        (A) 240 V

        (B) 232 V

        (C) 248 V

        (D) 320 V

        Answer: (C)

      155- The core loss when the transformer is connected to 4400 Volt 50 Hz source will be 

        (A) 306 W

        (B) 600 W 

        (C) 904 W 

        (D) 1004 W

        Answer: (C)

      156- The Core loss when transformer is connected to 4600 volt , 60 Hz source will be 

        (A) 907 W

        (B) 875 W

        (C) 603 W

        (D) 306 W

         Answer: (A)

       157- Impedance matching transformer are used for

        (A)  measuring low voltages and low currents

        (B) measuring high voltages and high currents  

        (C) stabilizing voltage fluctuations due to varying load   

        (D) minimizing the effect of harmonics

        Answer: (A) 

     158- The transformed power will be 

        (A) 620 W

        (B) 1240 W

        (C) 2480 W

        (D) 2760 W

        Answer: (B)

     159- The power conducted directly from the source to the load will be

        (A) 1240 W

        (B) 2000 W

        (C) 2760 W

        (D) 3000 W

        Answer: (C)

     Following two transformer are connected in parallel and deliver a total load of 300 kVA.
            
            Transformer 1                                  Transformer 2
      
     Rating = 150 kVA                                    Rating = 250 kVA
     6900/230 volts                                       6900/230 volts
     Ze= 9.4 in primary terms Ze = 5.8 in primary terms

     160- The load current will be

        (A) 100 A

        (B) 87 A 

        (C) 43.5 A

        (D) 25 A

       Answer: (C)





       

1 comment:

  1. Please someone show the detailed solution of Q144-147. Please someone send the answer to me as fast as possible. Tommorow is my exam.

    ReplyDelete