approval
and test specifications
of
the Association
of
German
Electrical En·
gineers (VDE), the electrical equipment
of
our
machines must hove
either
on
earthing
lead
or
double
insulation.
Inasmuch as
we
are
convinced
that
insulating is
more
effective than
earth
i
ng,
the electrical
equipment
incorporated in
all
Pfaff 260
and
360 sewing machines
is
doubly
insulated. This means
that
the normal insulation
(e.
g. between the
motor
winding
and
the laminations) is complemented
by
a second protective
insulation.
In
the case
of
the motors used
with
Cl. 260
and
360 machines, this
insulation consists
of
a plastic housing.
If
the normal insulation should
foil
(e
. g.
if
the
motor
winding
should be
scorched), the
additional
insulation
will
reliably
protect
the user
aga
inst elec-
tric
shock.
Since this
protective
insulation is
of
great
impor
t
ance
to
the safety
of
the user,
it
is subjected
to
a stringent test
at
our
factory.
In
the course
of
this test,
500-volt
A.
C. is
applied
to
the normal insulation,
while
4,.400-volt A. C.
is
applied
to
the
pro
tective insulation
of
the completed machine.
If
nei
ther
a
puncture
nor
a flashover has occured
during
a
per
i
od
of
one second, the
protective
insulation has, in effect, passed the test
with
20 times the
normal
load
of
220
volts.
The type
of
insulation used (double insulation)
is
indicated
on
the model
plate
of
the machine by
two
squares, one inside the other.
This type
of
insulation
affords
the
advantage
that
practically
no
leakage
of
current
will
occur
as a result
of
an
aged
normal
insulation, a defective
earthing
wire,
or
the use
of
spark arrester. The
danger
of
on
electric shock has thus
been
successfully eliminated.
The
foot
control
of
the machine, on the
other
hand,
is
connected
to
earth
by
means
of
a
safety
plug
. This connect
ion
posses from the
wall
outlet
to
the
plug
and thence
to
the
foot
control,
without
passi
ng
through
the machine itself.
The
ground
connection
will
be effective
only
if the safety
plug
is used together
with
a safety socket
that
is
actually
earthed.
Do
not
foil
to
impress this
fact
upon
your
customers as otherwise the earthing lead
would
be useless.
Warning
Whoever
installs
into
our
machines motors
or
other
electrical ports
of
a make
other
than
Pfaff
thereby violates the
German
Trade
Marks
Act
,
for
Pfaff sew-
ing
machines hove been
awarded
the VDE seal
only
on account
of
the high
quality
of
their
electrical equipment.
30
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