Table of Contents
Advertisement
8-3.
HIGH-FREQUENCY RADIATION
Installations
using high frequency
as an
integral
part
of
the power
source
will
produce
some
high-frequency
ra
diation. Such
radiation,
if the
signal strength
is sufficient
at
the
receiving
device,
can cause an
inconvenience
or
disruption
of
communications
or can cause
malfunction
in sensitive
electronic controls
and
systems.
The four
major
causes
of
high-frequency
radiation
are as
follows:
A.
Direct Radiation From The Power
Source
Direct radiation is that radiation
emanating directly
from
the power
source.
Radiation from the power line is
not
considered
to
be direct radiation from the power
source.
B.
Direct Radiation From The
Cutting
Circuit
Any
attachment
to
the
output
terminals of the power
source
is
capable
of
acting
as an
antenna
and
radiating
high-frequency
energy. Since direct
radiation from the
cutting
circuit is the
major
source
of
radiation,
it is
impor
tant to have
only
the
proper
torch attached.
C.
Conduction And Radiation
From The Power
Line
Most power lines
are
capable
of
conducting
high-fre
quency energy
which
may
cause
interference
directly
or
by
reradiation from these power lines.
Normally,
such
radiation is small when
compared
to that caused
by
ra
diation from the torch and work cables
or
leads.
D.
Reradiatlon
Radiation
from the
cutting
circuit
can
be
picked
up
by
un
grounded
metal
objects
or
unshielded
wiring
in the im
mediate
vicinity,
conducted
some
distance,
and
re
radiated. This
can
be
a
troublesome
source
of interfer
ence.
8-4.
LOCATION
Locate the power
source as
close
to
the
cutting
process
as
possible.
Also consider the
nearness
of
a
suitable
ground
connection when
selecting
a
site forthe
installa
tion of the
power
source.
Ideally,
the
power
source
should
be iocated in
an area
where there is
a
limited
amount of miscellaneous
wiring (lighting,
power, tele
phone,
communications,
and other unshielded conduc
tors)
located within the
cutting
zone.
Ungrounded,
me
tallic conductors in the
cutting
zone can
act
as
antennas
which will
pick
up,
conduct,
or
reradiate the
high-f
re
quency energy transmitted
by
the
cutting
circuit.
All mis
cellaneous
wiring
in the
cutting
zone
should be enclosed
in
grounded, rigid
metallic
conduit,
copper
braid,
or
some
other material
having
an
equivalent
shielding
eff i
ciency,
and
grounded
at
50 ft.
(15 m)
intervals
(see
Figure
8-1).
Keep
all unshielded and
ungrounded
wires
out
of the
weldIng
zone.
S.0084
Figure
8-1.
Requirements
To
Minimize Reradla
tion
Pickup
in
The
Vicinity
Of The
Cutting
Zone
8-5.
GENERAL INSTALLATION PROCEDURES
A.
Torch And Work Cables Or Leads
Position the torch and work cables
or
leads
as
close
to
gether
and
as
close
to
the floor
orground plane
as
possi
ble.
B.
High-Frequency
Assisted Plasma Arc
Cutting
(PAC)
Power Sources
When the
plasma
arc
cutting
(PAC)
power
source
is in
operation,
all service doors and
covers
must be
closed,
securely
fastened,
and
adequately
bonded
to
ensure
good
contact around the
entire
perimeter
of the open
ing. Except
for
changes
and
adjustments
allowed
by
the
manufacturer,
the
power
source
should
not
be modified.
Plasma Arc
Cutting (PAC)
Power Source
Place leads
on
floor
or
\
on
boards,
and
keep
them
3/4
to I
in.
(19-25 mm)
apart.
Figure
8-2.
General
Rules For Torch And Work
Cables Or Leads
C.
Grounding (Earthing)
The
Workpiece
It
is
recommended
that
the
workpiece
be
firmly
grounded.
This
ground
must
be made
by
grounding
the
workpiece
with No.
12
AWG
or
smaller wire
to
a
driven
ground
rod
or
to
a
water
pipe
which
enters
the earth
within 10 ft.
(3 m)
of the
workpiece.
Plasma Arc
Cutting (PAC)
~
Power Source
,
Ground
Electrical
Input
Supply
S-0085
OM-296
Page
21
Advertisement
Table of Contents
