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Restoring residual magnetism/fi eld fl ashing
The direct current necessary to magnetize the revolving fi eld is obtained
from the exciter. Upon starting the generator, current and voltage is
induced into the exciter by the magnetic lines of force set up by residual
magnetism of the exciter fi eld poles. Residual magnetism of the exciter
fi eld poles may be lost or weakened by a momentary reversal of the fi eld
connection, a strong neutralizing magnetic fi eld from any source, or non-
operation for a long time. If the generator fails to generate voltage after
it has come up to rated speed, it may be necessary to restore residual
magnetism.
To restore the small amount of residual magnetism necessary to begin the
voltage build up, connect a 12 or 24-volt battery to the exciter fi eld coil
circuit and fl ash as follows:
1. Open the output circuit breaker, and stop the engine.
2. Disconnect the exciter fi eld coil wires EF1 at the terminal EF1 and
EF2 at the terminal EF2, and connect the battery positive lead to the
fi eld coil lead EF1.
3. Flash the fi eld by touching the battery lead to the fi eld coil circuit
terminal EF2.
4. Disconnect the battery leads.
5. Reconnect the fi eld coil lead EF1 to terminal EF1, and reconnect the
fi eld coil lead EF2 to terminal EF2.
6. Start the generator, and check for voltage build up. Refl ash if
the generator output voltage does not build up, or fl ash with the
generator running, the fi eld coil wires connected to the regulator, and
a 3-amp or larger diode off the positive terminal of the battery per
Figure 19.
12 or 24 V
battery
+
3 amp or
larger diode
Voltage
regulator
F-
F+
Figure 19: Field fl ashing setup with the fi eld wires
connected to the regulator
-
EF1
EF2
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