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ELECTRICIAN - CITS



           EXERCISE 35 : Manual voltage control in DC Generator


            Objectives

           At the end of this exercise you shall be able to:
           •  make the connections of DC Generator
           •  start & run the Generator, and build up the voltage
           •  connect the load on DC Generator, and measure the load current & terminal voltage
           •  control the terminal voltage by varying the field current.

           Requirements

           Tools/Equipments/Instruments
           •  Combination Plier 165mm,                         •  Multi meter Digital, 3  digit     -1 No.
                                                                                    1/2
              insulated                     -1 No.             •  Rheostat 700 Ω, 5A             -1 No.
           •  Screw Driver 150mm, insulated    -1 No.          •  Tacho meter 3000 RPM           -1 No.
           •  Neon Tester 75mm, 500 V       -1 No.             •  Lamp load 5 KW                 -1 No.
           •  Electrician knife insulated     -1 No.           Materials/Components
           •  MG set (AC to DC) with DOL
              starter,DC shunt Generator                       •  Test lamp 60 W, 230 V          -1 No.
              5 KW, 250 V                   -1 No.             •  DPST switch 250 V, 32 A        -1 No.
           •  Voltmeter MC, 250 V           -1 No.             •  Connecting wire 2.5 sq.mm      - as reqd.
           •  Ammeter MC, 5 A               -1 No.             •  Cotton waste / cloth           - as reqd.
           •  Ammeter MC, 20 A              -1 No.

            Procedure

           TASK 1 : Check the MG set details & terminals
           1  Read and note down the specifications of MG set.

           2  Draw the circuit diagram of voltage build up and loading of DC shunt generator.
           3  Select the required meters and equipments for the experiment.


           TASK 2 : Starting the Generator and building up voltage
           1  Make the connection of prime mover AC induction motor with DOL starter.
           2  Make the connection of DC shunt Generator as per circuit diagram.

           3  Check all connections and switch ON the prime mover motor.
           4  Now build up the voltage in generator by increasing field current.
           5  Record the rated induced voltage, field current and speed of generator.


           TASK 3 : Loading of Generator and manual control the terminal voltage by field rheostat
           1  Connect the lamp load on generator terminals through DPST switch.
           2  Close the DPST / load switch, increase the load gradually on the generator and record the load current  &
              terminal voltage.
           3  As load current increases on generator, the terminal voltage tends to decrease.
           4  Control & maintain the terminal voltage to approx. 250 V by increasing the field current by manually adjusting
              field rheostat.
           5  Now decrease load gradually, and observe the decrease of load current & increase of terminal voltage more
              than rated voltage.



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