Specifications
7.6KW
BT
GENERATOR
SINGLE
PHASE
EXCITER
ROTOR/FIELD
Auxiliary windings group a, b
and
c. Locate the
three
ter-
minal
points
on
the exciter rotor for these auxiliary winding
groups.
Position
the exciter rotor
as
shown in the illustration
and count off
the
porcelain knobs from the
12
o'clock point
either
left
or
right
to
locate terminal points
a,
band
c.
Measure
the
resistance value between the pairs
of
terminal
points A
&
B,
B &
C,
and C &
A.
There
is
no
need
to
unsol-
der
these
connections unless a faulty reading appears.
If
this
occurs, unsolder and
verify
the winding
fault.
There should
be
no
continuity
found
between any
of
the three terminal
points
and
the
rotor shaft/case ground.
Auxiliary
Windings
1.0
-
1.2
Ohms
RED
&
WHITE
EXCITER
ROTOR
Rotating Field Wuulings.
R~fer
to the illustration above of
the exciter
rotor.
The
field
winding connections
are
noted
as
the (+)
and
(-) connections
of
the red & white striped wires.
Measure
the
resistance value with your ohmmeter between
these
two
connection points. These connections need not be
unsoldered
unless
a faulty reading appears.
If
this occurs
unsolder
the
connection and verify the resistance reading.
With
these
connections lifted, there should
be
no
continuity
to
the rotor
shaft.
This would indicate a short
to
ground with
these
field
windings.
Diodes.
Six
diodes are mounted on the exciter rotor;
they
rec-
tify the
AC
voltage produced by the
three
groups
of
auxiliary
windings
to
DC
voltages and supply this
DC
voltage
to
the
rotating
field
windings.
RESISTANCE
VALUE
tHJHMS
TRROUGH-lRE
DIODE
----------11
OHMS
INFINITE
I
I-YL....
BLOCKING
---1
.....
__
....--
____
.....
INFINITE------
The diodes
can
be easily checked
in
place with the use of a
common automotive 12-volt high beam headlight bulb,
some
jumper leads and the generator's
12
volt starting battery.
A short or
an
open
in
a diode
can
easily be found with
the
above without having
to
unsolder and isolate each diode
to
check it
with
an
ohmmeter.
NOTE:
Attempting
to
check
diodes
in
place
with
an
ohmmeter
will
give
erroneous
readings
on
the
diodes
due
to
the
auxil-
iary
winding's
connections.
When
leads
are
put
across
the
diode,
as
illustrated,
voltage
passes
through
the
diode
allowing
the
headlight
to
glow
brightly.
HIGH
BEAM
12
VOLT
BULB
GLOWS
BRIGHT
Reverse
the
leads across the
diode.
The diode should block
voltage passing through it,
and
the headlight should not
glow,
or it
may
glow
faintly.
HIGH
BEAM
12
VOLT
BULB
DOES
NOT
GLOW/IS
VERY
FAINT
a. Should
the
bulb not
glow
with leads connected
in
both
directions, the diode
is
open internally.
b.
Should
the
bulb
glow
with
leads connected
in
both
directions, the diode
is
shorted internally.
In
both a
and
b
above,
the
diode should
be
replaced.
Check the resistance
values
of the rotating
field
windings
and the integrity
of
the
resistors connected
between
the
field
windings.
Rotating
Field
Windings 7.0-8.0 ohm. (Reading
taken
between the
two
red
&
white
wires
connected
to
the
(+)
and
(-)
terminals.
of the exciter rotor
as
shown
in
the
illustration.)
Posi-resistor. (Infinite readings between
both
yellow
leads
lifted
from
the (+) and (-) terminals
on
the exciter
rotor.)
A
shorted posi-resistor
will
destroy the rotating
field
and
cause
the
AC
output voltage
to
drop
to
zero.
Engines & Generators
43