5-3 GENERATOR OPERATION
PERMANENT MAGNET ,-
COIL MAIN STATOR
FOR INITIALEXCITATION
ECEPTACLE
APPLIANCE
DIODE
CONDENSERCOIL
CONDENSER
Fig. 5-8
5-3-1GENERATION Of NO-LOADVOLTAGE
IVhen the generator starts running: the permanent magnet
As oneortwocondensers areconnectedtothecondensercoil,thesmallvoltageatthecondenser:z.
coil generates a minute current which flows through the condenser coil. At this time, a small flux
isproducedwithwhichthe magneticforceatthe rotor’s magneticpoleisintensified.Whenthis magnetic force is intensified, the respective voltages in the main coil and condenser coil rise up.
As the current !$$ increases, the magnetic flux at the rotor’s magnetic pole increases further. Thus the voltages at the main coil and condenser coil keep risingby repeating this process.
As AC current flows through the condenser coil, the density of magnetic flux in the rotor changes. This change of magnetic flux induces AC voltage in the field coil,;sand the diode rectifier in the field
coil circuit rectifies this AC voltage into DC. Thus a DC current flows through the field coil and magnetizes the rotor core to generate an output voltagein the main coil.
When generator speed reaches 2700 to 2800 rpm (50Hz type) or 3000 to 3300 rpm (60Hz type), the current in the condenser coil and field coil increases rapidly.
This acts to stabilize the output voltage of each coils. If generator speed further increases to the rated value, the generator output voltage will reachto the rated value.
5-3-2 VOLTAGE FLUCTUATIONS UNDER LOAD
When the output current flows through the main coil to the appliance, a magnetic flux is produced and
serves to increasecurrent :$$ in thecondensercoil.Whencurrent i@ increases,thedensity of magnetic
fluxacrosstherotorcorerises. As aresult,thecurrentflowinginthefieldcoilincreasesandthe
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