Blue Bird Coachworks 450 LXi, Руководство пользователя

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4-2 Generator
450 LXi Owner Manual
~ 4-2-12 ~
Rev. “C”
4-2.6.2 Field Flashing
The direct current (DC) necessary to magnetize the alternator fi eld is obtained from the exciter. Initially, upon starting the
generator, current fl ow and voltage are induced into the exciter armature by the magnetic lines of force set up by the 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 if the generator is not operated for a long period of time.
To restore the small amount of residual magnetism necessary to being the voltage build up, connect a battery from 6 to 32
volts to the exciter fi eld coil circuit. Normally, a battery of 6 or 12 volts is large enough.
Procedure for Field Flashing to Restore Residual Magnetism
Disconnect the exciter fi eld coil wire F+ at terminal F+.
Connect a batteries positive lead to the fi eld coil lead F+. Use 12 volt battery.
Connect the batteries negative lead to the fi eld coil circuit terminal C.
Disconnect the battery leads after approximately 3 to 5 seconds. If the battery is connected for too long, over heating and
subsequent damage to the exciter can occur.
Reconnect the fi eld coil lead F+ to terminal F+.
Start the unit and observe the generator build up.
Refl ash fi eld (steps 1 through 5 above) if the generator voltage does not build up.
4-2.6.3 Alternate Procedure for Field Flashing
Apply either an alternating current or a direct current voltage of approximately 12 volts to any tow generator leads. Do not
make a positive connection but rather touch the leads together until the generator voltage begins to rise and then separate
the leads. It is suggested than a 30 ampere fuse be inserted in the circuit to prevent any damage in case the build up voltage
is not removed quickly enough.
Start the generator and observe generator build up. Refl ash fi eld if generator output voltage does not build up. This procedure
should be performed by Trained Service Personnel only. (See Figure 1)
4-2.6.4 Testing Diodes with an Ohmmeter
Isolate the rectifi er assembly by disconnecting the lead from the main rotor and tree leads from the exciter rotor. Test each
diode by applying the probes of an ohmmeter to the anode and cathode.
A good diode will produce a meter reading of only a few OHM’s when the probes are applied in one direction, and a reading
of near infi nity when the probes are reversed. If both readings are high, or both are low, the diode is defective and must be
replaced.
Diode failure after 25 hours “run in” period is generally traceable to external causes such as overheating or a reverse current
fed into the alternator. To save excessive service time and call backs, it is a generally accepted practice to replace all diodes
where failure can be traced to external causes after the cause of the diode failure is identifi ed and corrected.
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6.
Each generator was subjected to a standard NEMA insulation test, which means 1000 volts plus twice the highest voltage
for which the generator is rated was impressed between the windings and the frame. All machines are insulated with a high
safety factor for the class of insulation used. The latest and newest in insulation and baking techniques are used.
The fi nest insulation job can be very quickly broken down by carelessly applying high voltage to windings in a moisture
saturated condition. Mishandling in this respect can easily cause a break down, making it necessary to return the generator
to the factory for repair, and consequent expense and loss of time.
NOTE: If the polarity of the exciter is reversed by fl ashing the fi eld, it may be corrected by interchanging
the battery leads.