Westerbeke 9.0 BCG Technical Manual page 195

Bridge Rectifier
The bridge rectifier is supplied AC voltage from the auxiliary windings in the generator stator (C-3) and the
compound transformer (0-3). The AC voltage measured across the AC terminals of the rectifier during en-
gine operation is listed below.
120 Volts 120/240
NIL F/L NIL F/L
11 - 21 Volts AC 11 -21 VoitsAC
Diodes in the rectifier convert this AC voltage to DC and supply it to the windings (A-2) 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 rectifier during engine operation is listed below.
120 Volts 120/240
NIL F/L NIL F/L
a -17 Volts DC a -17 Volts DC
Failure of the bridge rectifier will result in no strong field being produced by the exciter stator windings. A
weak field is present, due to the magnetism in the exciter stator, which will cause the generator to produce
residual voltage as discussed earlier in this text, page 185.
Testing the Bridge Rectifier for Fault(s) with an Ohmmeter
(1) Set ohmmeter scale on Rxl (+ DC). Zero the meter.
(2) Connect the (
+ )
lead from the meter to Point #4. With the (-) lead from the meter, momentarily contact
points #1, #2, #3 and #5. No deflection of the needle should occur showing infinite resistance.
(3) Remove the (
+ )
lead from Point #4 and con-
nect the (-) lead to Point #4 and, with the (+)
lead, momentarily touch Points #1, #2 and
#3. Points #1 and #3 should show an a-ohm
resistance
±
2 ohms. Point #2 should show
a 4O-ohm resistance
±
5 ohms.
(4) Touch Point #5 with the (+) lead. No deflec-
tion of the needle should occur.
(5) Place the ( +) lead of the meter on Point # 1
and the (-) on Point #3. No deflection of the
needle should occur (infinite resistance).
Reverse the connections and the same should
occur.
Should the rectifier fail any of the above tests, it
is defective and should be replaced.
RESISTANCE VALUES - at 70 0 F (210 C)
(Simpson Meter 260 Model)
_____ -Point '3
189
Westerbeke Generators