5. 4
POWER
SOURCE
CIRCUIT
5.
4 Power source circuit
A.
AC
generator
The generating principle
of
an
AC
generator
is
the
same
as
that
of
the
generator coil
of
the flyweel
magneto. By one
turn
of
the
magnetic steel,
the
flux
in
the
iron core
changes
the
direction
as
many times
<is
the
number
of
magnetic poles. That
is,
at one
rotation
of
the magnetic steel,
the
flux
in
the
coil
iron core
changes
as
many
times
as
the
number
of
(magnetic poles/2) cycles. Therefore, in accordance
to
this
change,
AC
voltage
is
generated at the gen-
erating coil. Magnetic force
changes
correspondingly
with
the direction
of
flux
in
the iron core (the greater
the
number
of
magnetic rotations
the
number
of
poles,
or
the
number
of
coil windings, the greater
will
be
the amount
of
generated voltage).
If
the magnetk
force,
number
of
magnetic poles,
or
the
number
of
coil windings
is
increased, a reduction
must
also exist.
(Refer
to
Fig.
5.
39)
A merit
of
the
AC
generator
is
that malfunction
rarely occurs
due
to
the
fact that simple construction
parts, subject ta wear, are not employed. The feature
.of coupling the
AC
generator and ignition coil
is
for
emergency start ;
this
is
impossible with a DC gen-
erator. As batteries with low capacity are employed
ln motorcycles, battery power
is
occasionally com-
pletely
discharged
due
to
carelessness
in
handling.
In
the battery ignition system,sparking
is
not obtained
until the battery
is
re-charged
or
replaced. However,
with
AC
generators, a large, induced voltage
is
ob-
tained during a lightly loaded period and
by
feeding
this voltage
to
the ignition coil through a rectifier,
sparks are obtained at
the
plug
even
when the battery
is
completely discharged,
by
using
the kick starting
system.
This
system
is
called
an
emergency start
system with circuit switching being performed
by
the
.combination switch.
On
the other
hand,
demerits
of
the
AC
generator
,(flywheel magneto, generating coil
of
magneto)
is
that
voltage regulation
is
insufficient
and
when a load ex-
ceeding the designated value exists,
an
excessive in-
.crease
or decrease
of
voltage
is
generated.
Attenuation
of
magnetic force does not occur during
oormaf
use.
Hence,
the
vehicle will not be rendered
•unusable
due
to
such
attenuation.
Even
if
magnetic
force
is
attenuated
due
to accident, design allows
for
rn-magnetizing. (Refer
to
Fig. 5)
fig.
5.
39
AC
generator
fig.
5.
40
AC
generator
construction·
SPECIFICATIONS
Primary
current:
Locked under normal.
temperature,
less than
3_A
al
12V.
Cranbhoft at 10,000rpm, less than 0.6A
at
12V.
Spork
capability:
More
than 7
mm
at
300
rpm (Baltery, 8
VJ.
E±)spark.
More
than 7
mm
al
10,000
rpm
!Battery,
12
VI,
EB
sparL
For measurentenf, the high tension lead
on
one
side
is
grounded through
·o
l
mm
gap and the
high
tension lead
or
the
other
side
is
connected to a
3
gap.
.
Note:
Use
the
high
tension
feod,
tiled
and white
®•
on the 0
spark side and connect to the
feh
cylinder plug.
Fig. 5.
41
Specifications
of
AC
generator
Fig.
5.
42
AC
generator
installed on engine
91
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