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Sec. 7
Page 128
GM COACH MAINTENANCE MANUAL
REGULATOR
magnetic field strengths are added when a reverse
current flows, but are opposed when charging cur-
rent flows to the battery. This gives a direction-
al effect which allows the relay to respond to a
moderate reverse current without interferring with
the maximum current flow.
The armature of the
overload relay carries a single contact point and
is connected to ground. Directly above the arma-
ture contact point is a fixed contact point which
is connected to the shunt winding of the circuit
breaker relay.
The contact points are normally
held closed by the tension of a flat spring attached
to the side of the armature.
Under normal conditions, operation of the ac-
tuating and circuit breaker relays is sufficiently
rapid to prevent the development of excessive re-
verse current from the battery when generator
voltage drops. However, in unusual circumstances
where there is a very sudden decrease in gener-
ator voltage, reverse current may build up rapidly
enough to reclose the actuating relay before the
circuit breaker relay has time to open. Reclosing
of the actuating relay, of course, prevents normal
opening of the circuit breaker relay since the
shunt coil remains energized. In such a case, over-
load relay exercises emergency control over circuit
breaker relay by interrupting ground connection of
circuit breaker relay shunt winding (fig.
20).
REGULATOR CHECKS
AND ADJUSTMENTS
The following checks and adjustments cover
only those operations which can be performed
while unit is mounted on the vehicle.
Certain
other adjustments are required when unit is com-
pletely rebuilt, however, rebuilding procedures
are not included in these instructions.
NOTE:
Because of the high currents
controlled by the carbon pile regulator,
it
is necessary to use insulated tools in ad-
justing
the
various
units in operation.
Short circuits to ground may seriously
damage the regulator.
A
non-magnetic feeler gauge must be used in
TO
SCREW-TUR
ST C
VOLTAGE
TP 5597
Figure
21-Circuit Breaker Relay Closing Voltage Adjustment
checking the front air gaps of voltage and current
regulators because of the strong magnetic fields
created during their operation.
Gauges may be
made of brass or stainless steel. Other equip-
ment required includes a 15 ohm - 15 watt vari-
able resistor and a .06-.08 ohm - 3000 watt fixed
resistor.
The variable resistor should have an
"OFF" (open circuit) position at extreme left and
must be large enough to permit accurate adjust-
ment. (Small resistors having relatively few steps
are not satisfactory for this purpose since the
voltage cannot be varied smoothly.)
Refer to "Specifications" at end of this group
for all current values and adjustment dimensions.
Figure 22-Actuating Relay Closing Voltage Adjustment
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