Bridge Rectifier - Westerbeke 5.0Kw BCDR Operator's Manual

7.6KW BT GENERATOR SINGLE PHASE
BRIDGE RECTIFIER
The bridge rectifier is supplied AC voltage from the auxiliary
windings in the generator stator «(::-3) and the compound
transformer (D-3). The AC voltage measured across the AC
terminals of the rectifier during engine operation is as fol-
lows:
120 Volts
NIL FIL
17 - 44 Volts AC
; 120/240 Volts
NIL FIL
. 17 - 44 Volts AC
Diodes in the rectifier convert this AC voltage to DC and
supply it to the windings of the exciter stator to induce a field
through which the exciter rotor revolves. The DC voltage
measured across the (+) and (-) terminals of the bridge recti-
fier during engine operation is as follows:
120 Volts 120/240 Volts
NIL FIL NIL FIL (
8 - 17 Volts DC : 8 - 17 Volts DC
Failure of the bridge rectifier will result in a weak field being
produced by the exciter stator windings. A weak field is pre-
sent, due to the magnetism in the exciter stator, which will
cause the generator to produce residual voltage.
BRIDGE RECTIFIER
POINT #1
POINT #4
Testing The Bridge Rectifier
For Faults With An Ohmmeter
(Meter used: Simpson 260)
1.
Set the ohmmeter scale on RXI (+ DC) and set the
needle to zero.
2. Connect the positive (+) lead from the ohmmeter to point
#4. Taking the ohmmeter's negative (-) lead, momentar-
ily contact points #1, #2, #3, and #5. The ohmmeter
should register no deflection for any of the points
touched.
3. Remove the positive (+) lead from point #4 and connect
the negative (-) lead to point #4 and, with the positive (+)
lead, momentarily touch points #1, #2, and #3. The ohm-
meter's needle should deflect when each point is touched,
showing a passage of meter voltage through the diodes in
the rectifier.
4. Leaving the negative (-) ohmmeter lead on point #4,
touch point #5 with the positive (+) lead. No deflection of
the needle should occur.
S. Place the positive (+) lead of the ohmmeter on point # I
and the negative (-) lead on point #3. The ohmmeter
should not register any deflection of the needle (no
deflection indicates infinite resistance). Reverse these
connections and the ohmmeter should again register no
deflection.
If the rectifier fails any of the previous tests (1 -4) it is
defective and should be replaced.
NOTE:
Different style/model meters may produce opposite
results from the above tests.
Engines
&
Generators
42