Alternator And Regulator; Alternator-To Test In Position - Rolls-Royce Silver Shadow Workshop Manual

Rolls- Royce Silver Snadow B
Bentley T Series
Workshop Manual
Chapter
M
Section
M5
ALTERNATOR A N D REGULATOR
C.A.V. Model AC 512 and 440 Regulator
Alternator
0
The
alternator
is a three-phase machine of the
revolving field and stationary armature type and i s
self limiting in current output. Rectification of the
output into direct current i s provided by six silicon
diodes contained in the slip ring end-shield and
connected in a three phase bridge circuit between
the stator and output terminals.
A
second rectifier
bridge is formed by using three auxiliary diodes in
a
I -
conjunction with three of the six main diodes and
2
these supply the energy for the alternator field coil
which is fed through slip rings and brushes. This
E
g
arrangement of auxiliary diodes prevents the battery
Z
from discharging through the field coil when the
alternator is stationary.
440 Regulator
The regulator i s fully transistorised with no moving
parts, requires no service attention and i s non-
0
repairable.
A
cut-out relay i s not necessary a s the
diodes in the alternator prevent reverse currents
from the battery flowing through the stator when
the machine i s stationary or when generating less
than the battery voltage.
Important The transistors in the regulator and
;5,
. r
diodes in the alternator are sensitive
N
to voltage changes and high
9'
V !
temperature, therefort, it i s essential
I -
that the following precautions are
taken to avoid damage to the
system when carrying out vehicle
maintenance:
T H E BATTERYMUSTNOTBECONNECTED
OR DISCONNECTED WHEN T H E ENGINE IS
0
RUNNING.
2.
\Yhenevt,r a lead is disconnec.ted it should be
identified in relation to its terminal to facilitate
reconnection. Short circuiting or reverse polarity
no matter how brief will cause immediate and
permanent damage to transistors and diodes.
3.
The battery must not be disconnected whilst
the alternator i s running nor should the battery be
connected into the system without first checking
for correct polarity.
4.
Do not use insulation testers on the regulator.
Maintenance
The charging system requires very little attention
but it should be kept free from dirt build-up and a
check made if it fails to keep the battery charged.
This may be due to a slipping drive belt.
1. Occasionally inspect the driving belt for wear
and correct tension and verify that the alternator i s
properly aligned with respect to the drive. (See
Drive belt
-
To adjust).
2. Keep the alternator clean with a cloth
moistened in paraffin or white spirit and ensure
that the ventilation slots and air spaces are clear
and unobstructed.
3.
Remove any dirt accumulated on the regulator
housing and ensure that cooling air can pass freely
over the casing.
Alternator-To test in position
1.
Connect a 0-50 volt first grade moving coil
voltmeter between the regulator negative terminal
and the positive terminal marked I l l .
2. Connect a 0-100 amp first grade ammeter in
series in the alternator positive line.
3. With the battery in a fully charged condition,
the system i s in correct working order when the
following sequrncc is observed:-