DESCRIPTION
GENERAL
An Onan DEH series electric generating set is a
complete unit consisting of an engine driven AC
generator, with standard and optional controls and
accessories as ordered.
ENGINE
The engine on the DEH is a Ford-Dorset
271
IE as
described in the engine manual. Basic measurements
and requirements will be found under
SPECIFICATIONS. For operation, maintenance and
service information, consult the Ford-Dorset manual.
AC
GENERATOR
The generator is an ONAN Type UR, 12
lead,
4-pole
revolving
field,
reconnectible, brushless unit. The
main rotor is attached directly to the engine flywheel,
therefore engine speed determines generator output
frequency. The 60 Hz set operates at 1800 r/min, the
50 Hz at 1500 r/min. Excitation is achieved as
foi
lows-
Residual alternating durrent from the stator winding
is applied to the voltage regulator, where it is
compared with a reference voltage, rectified- and
returned to the field winding of the exciter. Current
then induced in the exciter rotor is rectified and fed
into the generator rotor. This induces a current in
generator stator which is applied to the
load.
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 2.
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 battery
charging current.
Run-Stop/Reset-Remote Switch: Starts and stops the
unit locally or from a remote location. Resets engine
monitor relay in Stop/Reset position.
Warning Light: Indicates "Fault" in engine operation.
AC
Panel
AC Voltmeter Indicates ACgeneratoroutputvoltage.
Dual range instrument: measurement range in use
shown on indicator light.
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
1/1
Oth,
that the unit has run. Use itto keepa
record for periodic servicing. Time is accumulative,
meter cannot be reset.
Voltmeter Phase Selector Switch: Selects phases of
generator output to be measu red by the AC voltmeter.
OPTIONAL
EQUIPMENT
DC
Panel
Warning Lights: Eliminates the one "Fault" light and-
substitutes five indicator (see Figure 3) lights to give
warning of—
a. Overcrank
b. Overspeed
c. Low oil pressure
d.
High.engine temperature
e. Low engine temperature
Operation of these lights will be discussed in
con-
junction with engine monitor panel.
Reset Switch: Manual reset for engine monitor after
shut-down.
Lamp Test: Press to test warning lamp bulbs (when
engine is running only).
AC
Panel
AC Ammeter Indicates AC generatoroutput current.
Dual range in use shown on indicator lights.
Frequency Meter Indicates the frequency of the
generator output in hertz. It can be used to check
engine speed. (Each hertz equals 30 r/min.)
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