How to calculate the bare copper wire stranded pitch?

The main parameters of the stranding process are: stranding pitch, stranding coefficient, stranding direction
First, stranded pitch
1. What is the distance (h) advanced by a single stranded wire rotating along the stranded axis is called the stranding pitch. The ratio of pitch to diameter is called pitch ratio or pitch multiple.
Taking regular concentric stranding as an example, there is a relationship between the stranded pitch, the outer diameter and the unfolded length of a single wire within the pitch as shown in the figure.
From the figure, the twisted wire pitch calculation formula can be obtained as follows:
h=LSinα=πD´tgα
L=
Formula: h: stranded pitch length;
L: the length of a single line spread within one pitch;
D ́: outer diameter of the pitch circle, D ́=D-d;
D: Stranded wire outer diameter;
d: single line outer diameter;
α: spiral rising angle. 2. Measurement of stranding pitch
Measuring tools: vernier calipers, steel rulers, tape measures.
Measurement method: direct measurement method, untwisting method, scratch method.
3. Stranded pitch ratio
The pitch ratio is the ratio of the pitch length of the stranded wire to the outer diameter of the strand, which is called the practical pitch ratio
m =
It is expressed by the pitch of the stranded wire and the pitch diameter of the strand, that is, the ratio of the pitch to the pitch of the strand, which is called the theoretical pitch ratio
m´ = =
Second, the stranding coefficient copper industry
The twisting coefficient refers to the ratio of the actual length of a single wire to the length of the stranded pitch within a stranded pitch. The calculation formula is:
K =
where K: twisting coefficient;
L: the length of the single line of each pitch length in the stranded wire after unfolding straighter;
h: Stranded pitch length.
The relationship between the actual length of a single wire and the length of the stranded wire in the stranded wire is also expressed by the stranding rate. The stranding rate refers to the ratio of the difference between the actual length of a single wire and the length of the stranded pitch to the length of the stranded pitch within a pitch. The calculation formula is:
λ = ×100%
where λ: stranding rate;
L: Single line unfolded length;
h: Stranded pitch length.
Third, the twisting direction is opposite to the twisting direction of each layer of the wire of the concentric stranding, the reason is that the multi-layer wire is twisted into a round When the stranded wire is tensile, the turning torque generated by each layer cancels each other, preventing the single wire of each layer from rotating in one direction and loosening, and can also make the stranded wire produce the component force of the turning torque, and avoid the phenomenon of winding the stranded wire when it is not tightened.
The twisting direction is divided into left and right direction, for the stranding direction, the producer must pay attention to the product standard strictly stipulates the outermost twisting direction of the strand, the outermost stranding standard of the bare copper wire of the power cable is specified as the left direction, and the adjacent layer is twisted in the opposite direction.