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Section
8
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Generator
INTRODUCTION
The NHE and NHEL generator sets have a 4-pole,
revolving field generator with transformer voltage
regulation. All AC load connections are made
through long generator lead wires that connect
directly to a customer supplied junction
box.
A
circuit
breaker provides overcurrent protection for the
generator and also functions as an on/off switch in
the load circuit.
GENERATOR DESCRIPTION
The generator (see Figure 8-1) consists of thefollow-
ing major components:
Stator and Housing
Rotor
Voltage Regulating Transformer
Field Current Rectifier
Brushes
Wiring Harness
Stator and Housing
During generator set operation, AC current is pro-
duced in the windings of the stator. All stators have
two AC output windings (T1-T2 and T3-T4) for
powering the load and a separate winding (81-82) for
battery charging. All stators also have two lead wires
(Si and S2) that are used with the voltage regulating
transformer.
The stator mounts inside the generator housing and
is held in position with four clamps and four caps-
crews. A series of air-intake openings in the end of
the housing allow
cool
air to be drawn inside the
housing for generator cooling. The housing also pro-
vides a mounting point for the starter, rear bearing,
brushes, control, fuel pump, and voltage regulating
transformer. The complete stator and housing
assembly bolts to the engine-to-generator adapter.
Rotor
The 4-pole rotor provides the rotating magnetic field
that is required for generating an AC voltage poten-
tial in the stator windings. The DC current required
for field excitation is supplied through two slip rings
that mount on the rotor shaft.
The inner end of the rotor is connected directly to the
engine crankshaft using a tapered seat shaft coupling
and through-bolt. The slip ring end of the rotor is
supported bya single bearing. The bearing fits inside
the generator housing bearing.
Cooling airflow for the generator is provided by a
centifugal fan that mounts on the inner end of the
rotor shaft. The fan also serves as a mount for the
stator ring gear.
Voltage Regulating Transformer
The voltage regulating transformer (see Figure
8-2)
helps
to
provide stable generator output voltage
under varying load conditions. Voltage transformers
are constructed with two primary windings and a
single secondary winding. Each primary winding
(Hl-H2 and H3-H4) is connected in series with one of
the generator AC output windings. The transformer
secondary winding is connected in series with the
field current circuit. Taps on the secondary allow for
field current adjustments.
The voltage regulating transformer mounts on the
outside of thegenerator housing and is enclosed with
a special cover. The cover must be in place during
operation for transformer cooling.
Field Current Rectifier
(CR4)
TheCR4 rectifier isafull wave bridge rectifierthat is used
to rectify a portion of the generator AC output voltage to
DC
for field excitation. The positive and negative termi-
nals of the rectifier are connected to the generator
brushes. The rectifier mounts inside the generator set
control and may be accessed by removing the control
panel.
Brushes
The brush block assembly consists of a single brush
block with
two
brushes. The brush block mounts inside
the generator housing and can
be
accessed by removing
the small plate at the rear of the housing.
Wiring Harness
A
separate wiring harness is provided for connecting the
generator set to the RV electrical system. All lead wires
are stranded copper wire to withstand vibration. The lead
wires must be protected with flexible conduit which must
be provided by the RV manufacturer. A 3/4 inch conduit
elbow is provided to facilitate installation. The load wire
conductors are black, the neutral conductors are white,
and the ground conductor is green. The exit point for the
wiring harness is nearthevoltage regulating transformer.
GENERATOR OPERATION
Generator operation involves the control, stator, rotor,
voltage regulating transformer, brushes, and full wave
bridge rectifier. The schematic shown in Figure 8-3 is
intended as an example to help follow the generator
operating description. Always refer to the specific sche-
matic that correspondsto the model and spec number
of
the generator set when troubleshooting problems.
When the Start/Run/Stop button is placed in the Start
position, the rotating field (rotor) is connected to battery
Redistribution or publication of this document
by any means, is strictly prohibited.
Redistribution or publication of this document
by any means, is strictly prohibited.
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