5-3 GENERATOROPERATION
PERMANENT MAGNET
FOR INITIALEXCITATION
SURGEI
ABSORBERI
I
‘CONDENSER
Fig.
When the generator starts running, the permanent magnet
As one or two condensers are connected to the condenser coil, the small voltage at the condenser
coil generates a minute current@ which flows through the condenser coil. At this time, a small flux is produced with which themagneticforceatthe rotor’s magnetic pole is intensified.Whenthis magnetic force is intensified, the respective voltages in themain coil and condenser coil rise up.
As the current@ increases, the magnetic flux atthe rotor’s magnetic pole increases furtherThus. the voltages at the main coil and condensercoil 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 inducesAC voltage in the field coil,and the diode rectifier in the field coil circuit rectifies this‘ACvoltage into DC.Thus a DC current @ flows through the field coil and magnetizes the rotor core to generatean output voltagein the main coil.
When generator speed reaches 3000 to 3300 r.p.m. ,the current in the condenser coil and field coil increases rapidly.
This acts to stabilize the output voltageof each coils.If generator speed further increasesto the rated value, the generator output voltage will reachtothe ratedvalue.
5-3-2 VOLTAGEFLUCTUATIONSUNDERLOAD
When the output current@ flows through the maincoil to the appliance,a magnetic fluxis produced and serves to increase current @ in the condenser coil. When current @ increases, the density of magneticw
fluxacrosstherotor core rises. As aresult,thecurrentflowinginthefieldcoilincreasesandthe generator output voltageis prevented from decreasing.
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