Braided copper strips and twisted cables

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Real cross-sectional area: can be obtained by adding all the cross-sectional areas of each wire that make up the strip or braid.

Apparent cross-sectional area: is equal to the resultant area of the external dimensions of the braid, and it is equal to about twice of the real cross-sectional area.

Flexibility: depends essentially on the mechanical resistance of the material used and on its diameter.Usually, electrical applications require annealed electrolytic copper, red or tinned.

Highly flexible “ES”: single strand wire with a diameter of 0.05 to 0.07

Very very flexible “S”: single strand wire with a diameter of 0.10

Very flexible “ST”: single strand wire with a diameter of 0.15

Flexible “EF”: single strand wire with a diameter of 0.20

Semi flexible “F”: single strand wire with a diameter of 0.25 to 0.30

CHARACTERISTICS OF BRAIDS
Type Definition Advantages Disadvantages
TWISTED
CABLE
The strands are wound like a propeller.
Its flexibility is determined by its
winding pitch.
External appearance is a perfect cylinder. Available
in very long pieces without shunts. Low production
costs. Flexible in every respect.
Does not accept torsion, work hardening, if the
torsion is in the propeller’s direction, widening and
risk of breakage if torsion is in the opposite
direction. Strands may become wider when curved,
separation of strands when the strip is cut.
ROUND
BRAID
The strands are wound like propellers
but in opposite direction. The
winding pitch determines flexibility.
Extreme flexibility, more flexible than braids of equal crosssectional
area and than single stranded wires: when this
type of braid is cut the strands do not separate. Flexible in
all directions. Resists torsion to the point that the strands
do not widen. Square or rectangular sections with round
edges can be obtained, with a good flat flexibility.
Not a perfect cylinder. Great lengths cannot be
obtained, higher costs with respect to the braid
type.
FLAT
BRAID
The strands are wound like propellers
but in opposite direction. Its
cross-section is rectangular and not
extremely thick.
Great flat flexibility. Thickness is within limits with respect
to its width. Strong sections can be made by overlapping
many strips.
Limited sections. Low lateral flexibility. Limited
connection tightness due to overlapping of strips
which oppose each other when flexing occurs.
FLAT
TUBULAR
TYPE
BRAID
The strands are wound like propellers
but in opposite direction and tubular
shape.They are laminated in order to
take on a rectangular shape.This is
the most commonly used braid.
Great flat flexibility. They can be made very thick with
respect to its width. Strong sections can be made by
using only one braid or big sections can be made by
using many successive braids.
Poor lateral flexibility.

 

The current flow values are provided for information and are true for braids and twisted
cables, which are used horizontally. The real values may stray within tolerance, from
the values reported in the table, because it depends on the braid’s or cable’s
composition, i.e. number and diameter of the single strands of wire, external diameter
of the cable or external dimensions of the braid.

 

 

MAXIMUM ALLOWABLE CURRENT FLOW FOR ANNEALED BRAIDS AND TWISTED CABLES
Sezione nominale mm. 1 1,5 2,5 4 6 10 16 25 35 50 70 100 150 200 250 300 400 500 600 800 1000 1200 1500 2000 2500 3000
Corrente massima ammissibile A 18 21 30 40 55 85 120 150 195 250 300 370 480 610 700 780 950 1100 1250 1500 1800 2000 2200 2400 2750 3000

 

The values which are shown in the table below are to be considered at a room temperature
of 35°C (95°F) and the maximum operating temperature shall be 70°C (158°F).
The manufacturer is not responsible, under any circumstance for the values reported
in the table above.