Hudson 1955 Rambler, Technical & Service Manual

Page: 46 / 292

Circuit Breaker
The circuit breaker consists of an electro-
magnet and a set of contacts. The contacts are
mounted with one on a stationary bracket and
the other on a movable armature which is
controlled by the electromagnet. The movable
contact is mounted on a spring arm so that as
the contacts open and close a slight wiping
action is produced.
The electromagnet of the circuit breaker
has two windings, one, the shunt coil which
is connected across the generator output like
a voltmeter and the other a series coil
connected in series with the generator output
like an ammeter. These two coils are wound in
the same direction so that when the generator
is charging the battery, the magnetism of the
series coil increases the total magnetism.
When the battery discharges back through the
generator, the magnetism of the series coil
is reversed and the magnetism of the two coils
is opposed. This results in a decreased pull
on the armature and spring action opens the
contacts.
The sequence of operation of the circuit
breaker unit is as follows:
When the generator is not running, the
contacts are open. When the generator is
started, the voltage builds up at the armature
terminal and in the shunt coil and as soon as
it reaches the value for which the circuit
breaker is calibrated, there is sufficient
magnetism created by the shunt coil to pull
down the armature, closing the contacts which
automatically connects the generator to the
battery. With the contacts thus closed, the
current in the series coil is flowing from the
generator to the battery or in the same
direction as the current in the shunt coil,
so that the pull on the armature is increased
by the magnetism of the series coil.
When the engine is stopped and the
generator speed decreases, the voltage falls,
and as soon as the generator voltage drops
below the battery terminal voltage, the
current flows from the battery to the genera-
tor, reversing the direction of current in the
series coil so that the magnetism created by
the series coil opposes and reduces the
magnetism of the shunt coil. This reduces the
pull on the armature to a point where spring
action opens the contacts.
Voltage Regulator
The function of the voltage regulator is to
hold the generated voltage at a predetermined
value as long as the circuit values allow the
voltage to build up to the operating voltage.
The electromagnet of the voltage regulator
unit has a winding of many turns of fine wire
and is connected across the charging circuit
so that the system voltage controls the amount
of magnetism.
The contacts of the voltage regulator unit
are connected in the generator field circuit
so that the field circuit is completed through
the contacts when they are closed and through
a resistor when the contacts are opened. When
the voltage rises to a predetermined value,
there is sufficient magnetism created by the
regulator winding to pull the armature down.
This opens the contacts and inserts resistance
in the field circuit of the generator, thus
reducing the field current. The generated
voltage immediately drops which reduces the
pull on the armature to the point where the
spring closes the contacts. The output again
rises and the cycle is repeated.
These cycles occur at high enough frequen-
cies to hold the generated voltage at a constant
value and will continue as long as the voltage
of the circuit is high enough to keep the
voltage regulator in operation. With the
addition of a current load great enough to lower
the battery voltage below the operating voltage
of the unit, the contacts will remain closed
and the generator will maintain a charging rate
as limited by its speed or the current limiting
regulator.
Due to the effect of heat on the operating
characteristics of regulator windings, it is
necessary to compensate for the changes in coil
resistance when the regulator is operating
under varying temperature conditions. This is
accomplished through the use of a nickel iron
magnetic by-pass on the voltage regulator unit.
This shunt by-passes some of the magnetic flux
when the unit is cold and allows most of the
flux to act on the armature when the unit is
hot. Thus, when the coil is hot and not as
efficient, the magnetic shunt reduces the
amount of flux needed to vibrate the armature.
The compensation is usually more than enough
to offset the changes in regulator coil
resistance due to heat. The excess compensation
allows the regulator to operate at higher
voltages under cold operating conditions than
under hot conditions. This is necessary as it
requires a higher voltage to charge a battery
with its internal resistance increased by low
temperature.
Current-Limiting Regulator
The function of the current-limiting regulator
is to limit the output of the generator to its
maximum safe output.
The electromagnet of the current regulator
unit consists of a winding of heavy wire that
is connected in series with the generator
output. When the generator output reaches a
predetermined value, the current in the winding
produces enough magnetism to overcome the
spring tension and pull the armature down. This
opens the contacts and inserts resistance in
the field circuit of the generator. With the
field current reduced by the resistance, the
generator output falls and there is no longer
enough magnetism to hold the contacts open. As
soon as the spring closes the contacts, the
output rises and the cycle is repeated. These
cycles occur at high enough frequencies to
limit the output to a minimum fluctuation.
E L E C T R I C A L
5