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Determining
th
e
Rotative Speed of Generator Corresponding
to
the
Beginning of Excitation
Determine the
generator speed
during idling
and
under
load.
In o
rd
er
to determin
e
the
beginning
of excitation
during idling,
connect
the
generator as shown
in the
diagram (Fig.
37).
By gra-
dually increasing the
a
rm
ature speed,
observe
the vo
ltm
ete
r
read-
ings. In a
serviceable generator, the armature speed must
not
be
greater than 1350 r.p.m.
at a voltmeter
reading
of 6.5 V.
To
determine
the beginning
of
excitation
under
lo
ad, con-
nect
the generator as shown
in
the diagram (Fig.
38).
By
g radua
ll
y
increasing the
armature
speed
and,
at
the
same time,
loading the g
ene
-
rator (by varying
the rheostat
resistance) up
to
10
A, obser-
ve the
vollmele
r
readings. In
a se rviceab le
generator, the
ar
-
mature
speed
must not be
grea
-
ter than
1950
r.p.m
.
at a volt-
Fig.
37.
Dia-
gram
showing
the
connection
of generator
for
testing
under
idling
condi-
tions
f'ig.
38.
D
ia-
gram
show-
ing the
con-
nection
of
generator for
testing under
load
meter reading
of
6.5 V. Fluctuations in the
vo
lt
age will
indi
cate
that the brushes
are
fau.lty.
Sparking under the brushes
must
be
weak al
l
o\·er the
work
ing
s
uria
ces
of the brushes and
h
ave
a bluish tint. Heavy
sparking of
strawy colour and em ission
of
spa rks
from under
th
e
brushes in-
dicates
th at the bru
sh
assembly is out of order.
Checking the
Gen
erator
on Motorcycle
In
the absence of
a test bench,
the electriull characteristics
may
be
roughly determined
on an operating engine,
for
which purpose
place the
motorcycle on a
su
pport
and
use
a portable ammeter,
class 1.5,
with
readings
of
up
to 15 A, a voltmeter, class
1,
w
ith
read-
ings
of
u.p to 15
V, and loading rheostat
rated
for 2
n
at
permis-
s
ibl
e current of
up
lo
20
A.
In lhi
s
case, with the fourth
s pee
d
en-
gaged, the
spee
dometer
will
read 18 km/hr,
at a generator
speed
of
1350 r.p.m.,
and 27
krn /hr,
at
1950 r.p.m.
Dismantling
and Assembling the
Generator
To dismantle
the generator,
proceed
as
follow
s
:
uncotter and then
screw off
the nut
securing
the
gear,
remov
e
the
gear and its
key;
remove the g·enerator protective band
and gasket after first
un-
doing
the
coupling
screw;
unscrew two coupling bolts on the rear
cove
r;
107
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