ELECTRICAL EQUUPMENT
of the magnet on the armature is sufficient
(b) Cut-out
to overcome the tension of the adjusting
Cut-in voltage
:
12.7-13.3
spring. Drop-off voltage
:
8.5-1 1.0
Reverse current
:
3.5- 5.0 amp.
Tk
operation of
the
cut-out is as follms
:
The shunt coil is connected across the
3.
SERVICING
generator.
When the vehicle is starting,
the speed of the engine and thus the
voltage of the generator, rises until the
electro-magnet is sufficiently magnetised to
overcome the
s~rinp: tension and close the
(a) Testing in position to locate fault
in
charging circuit
If the generator and battery are in
order, check as follows
:-
W
cut-out contack. This completes the
circuit between the generator and the
battery through the series winding of the
cut-out and the contacts. The effect of the
charging current flowing through the cut-
out windings creates a magnetic field in
the same direction as that produced by the
shunt winding. This increases the magnetic
pull on the armature so that the contacts
are firmly closed and cannot be separated
by vibration. When the vehicle is stopping
the speed of the generator falls until the
generator voltage is lower than that of the
battery. Current then flows from the
battery through the cut-out series winding
and generator in a reverse direction to the
charging current. This reverse current
through the cut-out will produce a differ-
ential action between the two windings and
partly de-magnetise the electro-magnet.
The spring, which is under constant ten-
sion, then pulls the armature away from the
magnet and so separates the contacts and
opens the circuit.
Like the regulator, operation of the cut-out
is temperature-controlled by means of a
bi-metallic
tensioning spring.
E.
SETTING
DATA
(a) Regulator
Open-circuit setting
at 20°C. and 1500
dynamo r.p.m.
:
15.616.2 volts.
NOTE
:
For ambient temperatures
other than 20°C. the following allow-
ances should be made to the above
setting
:-
For every 10°C. (18"F.)above 20°C.
subtract 0.3 volt.
For every 10°C. below 20°C. add
0.3 volt.
Ensure that the wiring between
battery and regulator is in order.
To do this, disconnect the wire
from control box terminal
"
A
"
and connect the end of the wire
removed to the negative terminal
of a voltmeter.
Connect the positive voltmeter
terminal to
an
earthing point on
the chassis. If a voltmeter reading
is given, the wiring is
in
order
and the regulator must be ex-
amined.
(ii)
If there is no reading, examine
the wiring between battery and
control box for defective cables or
loose connections.
(iii)
Re-connect the wire to control
box terminal
"
A."
(b) Regulator Adjustment
The regulator is carefully set during
manufacture and, in general, it should
not be necessary to make further
adjustment. If, however, the battery
does not keep in a charged condition,
or if the generator output does not fall
when the battery is
fdy charged, the
setting should be checked and, if
necessary, corrected.
It is important before altering the
regulator setting to check that the low
state of charge of the battery is not
due to
a
battery defect or to slipping
of the generator belt.
(i) Electrical Setting
It is important that only a good
quality MOVING COIL VOLT-
METER (0-20 volts) is used when
checking the regulator. The elec-
trical setting can be checked with-
out removing the cover from the
control box.
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