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DESCRIPTION
GENERAL
An ONAN DDB series electric generating set is a
complete unit consisting of' an -engine driven AC
generator, with controls and accessories as ordered.
ENGINE
The engine on the DDB is a John Deere 6329D as
described in engine manual. Basic measurements
and requirements will be found under Specifications.
However, the engine used for your unit may have
variations due to optional equipment available,
therefore the John Deere manual should be con-
sulted.
AC GENERATOR
The generator is an ONAN Type UR, 12 lead, 4 pole
revolving field, reconnectible brushless unit. The
alternating current is generated in the statorwinding.
The alternator rotor, attached directly to the engine
flywheel turns at engine speed. Therefore, the speed
at which the rotor turns, determines generatoroutput
frequency. The 60 hertz set operates at 1800 rpm and
the 50 hertz at 1500 rpm. Excitation is achieved by
feeding AC output to a voltage regulator, where it is
compared with a reference voltage in the regulator,
rectified and returned to the field of the exciter, then
to the exciter armature, rectified and fed to the
generator field. The UR generator is available in 3-
phase and single phase. Excitation and regulation are
the same for either unit.
CONTROL PANEL
The following is a brief description of each of the
standard controls and instruments located on the
face of the panel. See Figure 1.
DC PANEL
Panel Light and Switch: Illuminates control panel.
Oil Pressure Gauge: Indicates pressure of lubricating
oil in engine (wired to a sensor unit located on the
engine).
Water Temperature Gauge: Indicates temperature of
circulating coolant in engine. (Wired to a sensor unit
located on the engine.)
Battery Charge Rate DC Ammeter: Indicates the
battery charging current.
Run-Stop/Reset-Remote Switch: Starts and stops the
unit locally or from a remote location.
AC PANEL
AC Voltmeter: Indicates ACgeneratoroutputvoltage.
Dual range instrument: measurement range in use
shown on indicator light.
AC Ammeter: Indicates AC generatoroutput current.
Dual range instrument: measurement range in. use
shown on indicator lights.
Voltmeter-Ammeter Phase Selector Switch: Selects
the phases of the generator output to be measured by
the AC voltmeter and AC ammeter.
Voltage Regulator: Rheostat, provides approximately
plus or minus 5% adjustment of the rated output
voltage.
Exciter Circuit Breaker: Provides generator exciter
and regulator protection from overheating in the
event of certain failure modes of the generator,
exciter and voltage regulator.
Running Time Meter: Registers the total number of
hours, to 1/10th that the unit has run. Use it to keep a
record for periodic servicing. Time is accumulative,
meter cannot be reset.
Frequency Meter: Indicates the frequency of the
generator output in hertz. It can be used to check
engine speed. (Each hertz equals 30 rpm.)
OPTIONAL EQUIPMENT
DC PANEL
Warning Lights: Eliminates the one "Fault" light and
substitutes five indicator lights to give warning of —
a. Overcrank (failed to start)
b. Overspeed
c. Low oil pressure
d. High engine^t.emperature
e. Low engine temperature
Operation of these lights will be discussed in con-
junction with engine monitor panel.
Warning Lights: Indicates "Fault" in engine operation.
Reset Switch: Manual reset for engine monitor after
shut-down.
Lamp'Test: Press to test warning lamp bulbs (when
engine is running only).
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