MEASURING
RESIDUAL
VOLTAGE
No-LOAD
VOLTAGE
The amount
of
no-load voltage produce<t
by
the generator
9an
.
be
an indicator
of
where
in
the
generator the problem/fault:
may lie.
Residual Voltage 1
0-14
Vol.ts
[6
Stud] .
This
voltage is the
AC
voltage produced by the generator from
magnetism in the exciter stator field.
This
voltage is measured
between the
AC
Neutral
8nd
Hot
leg(s) with no-load
on
the
generator running
at
60 hertz.
The
presence
of
residual voltage is an indication that the
following generator components
are OK.
Exciter Rotor
B-1
a, b, & c and
B-2
Rotating Field B-3
Main Stator
c-1
and c-2
Compound Transformer
0-1
and 0-2
The fault lies in one
or
more
of
the following
components in the exciter circuit.
Exciter Stator
A-1
[and A-2
if
applicable]
Bridge Rectifier G
Selector Switch
·pf
applicable]
Main Stator Auxiliary Windings
C-3
Compound Transformer Auxiliary Winding
0-3
12
VOLT
EXCITATioN
Twelve (12) volt
DC
excitation
applied
to
the exciter stator
windings should
cause
the generator
to
produce
between
140-150
voltsAG·m~ured
between
the
Line
and
Neutral.
(Normal Excitation
8-9
volts
DC
no
load)
SOLENOID
r--::l
\
'I
\
I
\
\
.I
.
STARTER
MOTOR
EXCfll~GTHE
GENERATOR
wri"H
12
vdLT$
.
DC(+)
to
LED
and
CJC{-)
to
9;ound. .
Keeping
the
EXCITER
CIRCUIT
polarity conect.
FRAME
Correct voltage produced with 12 volts excitation indicates
the fault is
in
one
or
more
of
the above listed components
G, C-3
or
D-3 •
If
the generator does
not
produce the correct voltage [140-
150V
with excitation, then also include the rotor components
as possible faults.
The
Absence
of
any voltage from the
generator
indicates a fault with the main stator windings
c-1
and C·2 and/or the compOund transformer windings 0·1 and
D-2 or possibly a
shortedthermister.
Apply 12 volt
DC
excitation to the exciter stator windings
as illustrated. A fault
in
the main stator and/or compound
transformer windings such
as
a short will cause the generator
engine
to
load
down
and
the shorted windings to eventually
produce smoke
as
the excitation is continued.
Voltage output greater than residual and' less than rated output
35-100 volts indicates a fault
in
the exciter rotor/field
B-1,
B-2
or
B-3. Excitation
of
the generator should produce a partial
rise in voltage
output
and,
when removed, the voltage will
return
to
the
original
low
our;:;~.
BRIDGE
RECTIFIER
WIRING
The
~lustration
below
shows
the
color
cod~d
wires at the two
AC
terminals
and
the
color
coded wires
at
the ( +) and (-)
DC
tenninals,
·Hole: When removing
or
reinstalling connections, maintain
correc(polarity connection
on
the ( +) and (-) DC terminals.
{6S11JD)
WIRE
CONNECTIONS
TWO
GREEN
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