Where:
H =
Resistance
ratio
of
individual
strands
Following
is an
example
of
the
calculations
required
to
when
isolated
(taken
from
Table
1 or 2)
evaluate a
Type
2
Litz
construction
consisting
of
450
strands of 40 AWG single-film polyurethane-coated
wire
G =
Eddy-current
operating
at
100
KHZ.
This
construction,
designed
with
basis factor
two
bunching
operations
and
one
cabling
operation,
would be
written
5x3/30/40
(NEW
uses
x
to
indicate
F =
Operating
frequency in HZ
a
cabling
operation and / to indicate a
bunching
oper-
ation.)
N =
Number
of strands in
the
cable
DI
= Diameter of
the
individual
strands
over
the
1.
Calculate
the
D.C.
resistance
of
the
Litz
copper
in inches
construction
using
formula
3.
DO
= Diameter of
the
finished
cable
over
the
strands in inches
K = Constant
depending
on N, given in
the
following
table
2.
Calculate
the
A.C.
to
D.C.
resistance
ratio
using
formula
2.
The
D.C.
resistance of a
Litz
conductor is
related
to
the
following
parameters:
3.
The
A.C.
resistance
is,
therefore,
1. AWG of
the
individual
strands.
1.0344
x
2.70
or
2.79
ohms/1000
ft.
2.
Number
of strands in
the
cable.
The
value
of
Litz
can
easily be seen if
the
above
3.
Factors
relating
to
the
increased
length
of
example
is
compared
with
a
solid
round
wire
with
the
individual
strands
per
unit
length of
cable
equivalent
cross
sectional
area,
65.8
mils in diameter.
(take-up).
For
normal
Litz
constructions a
Using
the
same
operating
parameters,
the
D.C.
1.5% increase in
D.C.
resistance
for
every
resistance
is
2.395
ohms/1000
ft.
However,
the
bunching
operation
and
a 2.5% increase in
A.C./D.C. resistance
ratio
increases to approximately
D.C.
resistance
for
every cabling
operation
21.4
making
the
A.C.
resistance
51.3
ohms/1000
ft.
are
approximately correct.
The
following
tables
list
examples
of
Litz
The
formula
derived from
these
parameters
for
the
D.C.
constructions
which
can
be
manufactured
by
resistance of
any
Litz
construction
is:
New
England
Wire
Technologies.
These
are
categorized
by
operating
frequency
and
by
equivalent
AWG
size.
Round,
braided
and
rectangular
Litz
conductors
are
shown
separately to
provide
the
greatest
possible
selection
for
any
design
application.
Where:
RDC
=
Resistance
in
Ohms/1000
ft.
RS
=
Maximum
D.C.
resistance
of the individual
strands
(taken
from
Table
2)
NB
=
Number
of bunching
operations
NC
=
Number
of cabling
operations
w w w. n e w e n g l a n d w i r e . c o m
NS
=
Number
of
individual
strands
Te l : 6 0 3 . 8 3 8 . 6 6 2 4
©
2005
New
England Wire Technologies
131
