Aluminum stranded conductor dc resistance measurement method

For aluminum stranded conductor dc resistance measurement, many companies have also made a lot of research.In GB3048, the resistance when measuring the voltage and current of the distance, measure the current size and so on all the rules.Qualified for single use normal process of stranded wire core, still have to discuss problems in actual measurement, such as potential end shape on the measurement results, the influence of four-terminal method of resistance measurement of key points and how to realize the measurement of current uniform, etc.
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1.Twisted wire core insulation, the single wire in the electric current is along a single line into spiral flow, and the whole single wire line core reliably with the current introduction.Calculation of 1 m long stranded wire length of each layer, according to the formula of parallel resistance, dc resistance formula for computing the stranded wire, such as:

Actual twisted wire core still exist certain conductance between single wire, the size of the conductance associated with monofilament surface conditions.Conductivity is made with dc of wire core in completely along the single spiral flow, is part of the current along the monofilament into axial flow.The wire core dc resistance than current along the monofilament completely into smaller spiral flow.Because after stranded aluminium resistance of single wire has no obvious change, under the single qualified, even after considering the wire core cable length increased by 1%, twisted wire core resistance still has a certain margin.

2. The reasons of the measured values are not qualified
In the winding resistance is unqualified phenomenon, the reason is the resistance measurement to measure current not evenly through the sample.
All the monofilament wire core reliably with the current introduced, and the monofilament wire core insulation current flows along the monofilament into a spiral.So in the case of monofilament diameter is the same, homogeneous structure, cross section perpendicular to the line on the flexible cables core sample should the equipotential surface, in the cross section of potential difference between the monofilament is zero.In allelic case, voltage potential difference between side won't because of the shape of the voltage clamp, and ways of contact with the sample and the sample of the clamping force changes in the surface changes.

Measuring the winding resistance of fixture shapes are now a knife shape and round shape, by tightening bolts pressure on sample.As a result of the existence of monofilament aluminum surface oxidation film, when when the measured current is introduced through this form jig sample, its current points Cloth is often uneven, the winding outer filament current density.The phenomenon is serious with the increase of stranded wire section.

V current fixture than the sword shape, round ring current clamp has greatly improved, but still cannot make current to achieve the ideal state of uniform. Uneven distribution of the measured current to make 1 m away from the two voltage is the voltage difference, is greater than the uniform measure electricity shed the voltage difference between the two voltage side.In this case, the voltage terminal fixture shapes, also often cannot work pressure for further improvement.Therefore, the key is how to measure to solve the problem of resistance measurement of uniform current and voltage clamp requirement, can make the measuring current is measured and the necessary.