Resistance Values Of Components - Westerbeke 9.0 BCG Technical Manual

RESISTANCE VALUES OF COMPONENTS
(BCD and BCG models, as noted)
A. Rotating Field/Auxiliary Windings and Diodes
Two sets of windings are found on the rotating field
An electrical field is produced around these windings by the passing of DC voltage through them. As
these windings rotate, this field passes through the main stator windings inducing an AC voltage that is
available at the terminal block to be directed to a load. A separate group of windings for the battery charg-
ing circuit is effected by this rotating field. These windings produce an AC voltage that is directed into the
bridge rectifier that converts it to DC voltage for the battery charging controller.
1. Rotating Field/Auxiliary Windings
BCG 4.0KW: 3.8 Ohm
BCD 4.4KW: 3.8 Ohm
BCG 6.5KW: 4.0 Ohm
BCD 6.0KW: 4.0 Ohm
To check the resistance values, rotate the engine's crankshaft to position the diode(s) on the gener-
ator's shaft at 12:00
0'
clock. To make a quick check of these windings, presume the diode is OK, and
place one of the ohmmeter's leads on the connection at the top of the diode and the other lead at the
connection at the base of the diode. Compare readings with the value above. If a distinct difference is
noted in the ohm value, carefully unsolder the lead on the top of the diode and remove the diode from
the rotor using a thin walled, deep well 11 mm socket (7/16 inch equivalent).
NOTE: The shield in front of the diode can be bent carefully out board to make access to the
diode better.
With the diode removed, both leads for the
first group of rotating field/auxiliary windings
will be isolated with no interference from a
possibly faulty diode.
Check the resistance value of the rotating
windings by placing the ohmmeter's leads
across the two exposed leads.
Also verify that no continuity exists between
these windings and the rotor shaft by leaving
one ohmmeter lead attached to the winding
lead and the other ohmmeter lead touching
the shaft: no continuity should exist. If con-
tinuity is found, a short exists.
Repeat this same check on the second group
of windings. Rotate the engine's crankshaft
180
0
to position the second diode and con-
nections at 12:00 o'clock.
Diode
Rear Carrier Bearing
Diode
203
Westerbeke Generators