Bt Generator Troubleshooting (Chart) - Westerbeke 11.5KW-60Hz Service Manual

\
\
BT GENERATOR TROUBLESHOOTING
Exciter Rotor/Field
1. Auxiliary windings group a, b and
Co
Locate the thre~
tenninal 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 ternlinal points
a, b and c. Measure the resistance value between the pairs
of terminal points A
&
B, B
&
C, and C
&
A. There is no
need to unsolder 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 ..
REDN/HITE (RED)
2. Rotating Field Windings. Refer 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 read-
ing 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.
3.
Diodes. Six diodes are mounted on the exciter rotor; they
rectify the AC voltage produced by the three groups of
auxiliary windings to DC voltages and supply this DC
voltage to the rotating field windings.
The diodes can be easily checked in place with the use of
a common automotive 12-volt high beam head1ight 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.
11,DHMS THROUGH THE DIODE
-+,---11 OHMS'·
RESISTANCE VAlUE
INFINITE
rllJ~=----I------
BLOCKING~-II .~
INFINITE •
NOTE: Attempting to check diodes in place with an ohm-
meter will give erroneous ,readings on the diodes due to
the auxiliary winding's connecti()ns.
4. When leads are put across the diode, as illustrated, volt-
age passes through the diode allowing the headlight to
glow brightly.
b
12V ilATIeRY
High beam 12V bulb
glOWS bright.
S. Reverse the leads across the diode. The diode should
block voltage passing through it, and the headlight should
not glow, or it may glow faintiy.
a. Should the bulb not glow with leads connected io both
directions, the diode is open internally.
b. Should the bulb glow with leads connected in both
directions, the diode is shorted ioternally.
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.
12VBATIERY
6. Rotating Field Windings Readings taken
between the two red
&
white wires connected to the
(+)
and ~) tenninals of the exciter rotor as shown.
7. Suppressor. Infiuite readings between both yellow leads
lifted from the
(+)
and (-) terminals on the exciter rotor.
A short in the suppressor will cause a loss of the rotating
field. AC output voltage will drop to zero.
~
WESTERBEKE
Engines
&
Generators
83