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ELECTRICIAN - CITS



           EXERCISE 32 : To build up the voltage in DC compound

                                      Generator

            Objectives

           At the end of this exercise you shall be able to:
           •  check and identify the terminals of DC compound Generator
           •  start & run DC compound Generator with prime mover
           •  build up the voltage in DC compound Generator
           •  record the field current & induced voltage in the Generator and plot OCC graph.

           Requirements

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

            Procedure

           TASK 1 : Check the MG set details & terminals
           1  Clean the MG set with cotton waste and read its specifications.

           2  Draw the circuit diagram of voltage build up of DC compound generator.
           3  Check and identify the terminals of MG set (AC induction motor and DC compound Generator)



           TASK 2 : Connecting & Starting of MG set
           1  Make the connection of prime mover AC induction motor with DOL starter.
           2  Make the connection of DC compound Generator with field rheostat and meters.
           3  Check all connections and keep the rheostat in cut-in position.
           4  Switch ON the mains and start the prime mover AC induction motor coupled with DC compound Generator
              and measure the speed with Tacho meter.


           TASK 3: Build-up the voltage in DC compound Generator
           1  On starting of MG set observe & record the induced residual voltage in voltmeter.

           2  Slowly increase the field current in DC compound Generator by adjusting field rheostat.
           3  Further increase the field current until rated voltage is build up in DC compound Generator.
           4  Record the field current and full rated voltage build up in DC compound Generator.
           5  Reduce the voltage to zero by adjusting field rheostat and stop the prime mover motor.

           6  Plot the graph to indicate the field current (IF) & induced voltage (E )
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