Honolulu star-bulletin. [volume] (Honolulu [Oahu, Hawaii]) 1912-2010, 1917-03-03
NEWS AzD PRACTICAL INT2RMh1zATIoNs s5a1ea


-,~ ne eieClTfcdl BeucIdlOIs ~ 10 ~
plication TO the motor Is almost al
ways used in combination with a
storage battery. The generator Is used
TO charge the battery and TO product
a current in the various electrical de
vices on the car while the generate;
IS IN operation The battery serves a:
a sort Of reservoir. In which electriea
enargy may be stored and then uset
when the generator itself is not oper
atIng. A battery and generator ar
shown connected in series In Fig.
The positive terminal of the generate
is connected to the positive termins
of the batteries and their negative ter
minals are connected. The effective
pressure acting in such circuit l.
equal to the difference In the pressura
produced by the generator and tho
pressure produced within the battery
II these two pressures are equal tn
value OF the effective pressure VII
be zero and there Will be no current II
the circuit II the pressure producet
by the generator exceeds in value the
pressure produced by the battery there
will be an effective pressure acting ir
the circuit and its direction will cor
respond 20 that OF the larger pres
sure, or the pressure of the gener
ator. The current produced by this
effective pressure will charge the bat
terry and the value Of the current viii
be equal to the effective pressure
divided by the total resistance Of the
current. including the internal resist
kance Of the battery. the resistance OF
: the connecting wires and the resist
ance OF the armature winding OF the
generator.
II the pressure generated in the
armature winding OF the generator Is
less than the pressure OF the battery
then the direction Of thu battery pres
sure and the battery will discharge
instead OF being charged. The calue
OF the current will, as in the previous
case be equal to the effective pres
sure divided by the total resistance
Of the circuit.
Since the pressure generated in the
armature winding Of the generator
may vary In value from zero on up.
depenhlng upon its speed and field
control. Il is apparent that some
means must be provided for control
ling the connection between the gen.
orator and the battery In order that
the battery win not be allowed to dis
charge through the generator whom
the pressure OF the generator becomes.
lower than the pressure OF the bat
terry. The object OF the cutout may.
be understood BY use OF the simple
diagram given In Fig. q An electro
magnet. NJ has q winding OF large
number Of turns, and this winding Is
connected directly to the terminals OF
the generator The resistance OF the
winding Of this electrO-magnet is usu-
ally such that very small current
passes through e In comparison to the
total current output of the generator.
An armatnre. "A, carried on spring
Bivoted 81 It's LETT hand end and carry
ing contact point on its right hand
end is mounted near the core Of the
electro-maenet.
Action 81 Device
This ermature Is usually held away.
from the core OF the eleetr0-magnet by
means OF the springs, and the movable
contact point c Is not in contact with
the stationary contact point. The con-
nections- Of the generator and battery
are clearly Indicated In the figure.
Now. as the pressure generated in the
armature Of the Generator increases
there will be an increase in the cur
rent in the winding OF the electro
magnet nj. and the tension Of the
spring may be so adjusted that the
armature A pulls up the desired value.
The tension In the spring is usually
so adjusted that the generator pres
sure is a little higher than the battery
pressure when the circuit is com.
pleted, and the battery will always
start TO charge When the pressure
OF the generator decreases, due to any
cause. there Is a decrease in the cur
rent in the winding OF the electro
magnet NJ and the magnet pull it pro-
duces on the armature A decreases In
value. II the pull Of the spring s
exceeds. the magnet pull the armature
viii move away from the core Of the
electromaenet aud the circuit be-
tween the battery and generator will
be broken af the contact c.
The cutout whose connections and
arrangement are shown in Fig would
be satisfactory for closing the elecfri-
cal circuit connecting the generator
and battery, but would not open IL
properly In practise for the following
reasons: In theory the spring S
would pun the armature away from
the core OF the electro-magnet when
the electrical pressure generated in
the srmature OF the generator dropped
below value which would produce
the necessary current in the winding
to hold the armature up. The fol-
lowing action, however takes place in
actual practise: When the electrical
pressure Of the generator exceeds
the electrical pressure of the
battery the direction OF the current
in the battery, generator and winding
OF the electro-magnet will be as indi-
Gated by the three arrows In Fig. 3.
II there is decrease in the electrical
pressure Of the generator. due to any
cause. or an increase in the electrical
pressure of the battery and the two
pressurcs become equal in value.
there win be no current in the circuit