EXPERIMENT: SELF-EXCITED D.C. SERIES GENERATOR Make an Observation and Analysis

Question

EXPERIMENT:
SELF-EXCITED D.C. SERIES GENERATOR

Make an Observation and Analysis based on the data gathered in the experiment. At least ONE PARAGRAPH. No need to draw illustrations.

PROCEDURES 1. Before performing thie experiment, ensure firet that the bruahee of the DC Motor/Generator are adjueted to the neutral point. 2. Couple the Synchronoue motor ueing a timing belt. Then connect the eet-up hown n Fig. 5.1 Synchronous Generato DC MOTOR 120/205 Vac Fig. 5,1 3. Connect the terminal 4, 5, and 6 of the eynchronoue motor windnge to wye connection and the other ende (termindle 1, 2 and 3) to a fixed three phase AC source, termindle 1, 2, 3. 4. Connect the reeietive loade in paralel then connect them to the generator. Set the reaietancee witchea for no-load poeition. Turn on the power upply. The motor and the generator ehould atart running at thie moment. 6, Set the Reeietance Module to a load value of 57 7. Repeat proceduree 6 but eetting the load to the valuee ndicated in Table 5.1. If the voltage ie not buildng up, interchange

Explanation / Answer

External characteristics of self excited D.c series generator :

With increase of load, Terminal voltage of machine increases slightly. but when it reaches maximum value it starts

decreasing due the armature reaction which causes demagnetization. After that it gives constant output current

irrespective of load resistance this is because field is in series with armature when load current is increased field

current also increases but after saturation of magnetic field no further slight increase in terminal voltage. but

continuous increase in load current causes voltage drop due to demagnetizing effect of armature reaction and

hence terminal voltage decrease with increase of load current. due to this reason self excited dc series generator is

known as constant current generator.

External characteristics of seperately excited D.c generator :

When load current increase terminal voltage decrease due to armature reaction and ohmic voltage drop. this drop

in voltage can be maintained easily with increasing seperatly excited field circuit current . unlike self excited

generator here field is not in series with armature but have diffent circuit .hence seperately excited

dc generator can operate with various loads while maintaining terminal voltage through external field circuit. so

seperately ecited dc generator is known as constant voltage generator.

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