electrical linear resistance versus weight … · 2019. 8. 15. · astm standards b8-11...

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OUR DRIVING FORCE

ELECTRICAL LINEAR RESISTANCE VERSUS WEIGHT MEASUREMENT OF CONDUCTORS –

WHAT BENEFITS CAN WE EXPECT?

BORIS DARDEL, VINCENT ARBET-ENGELSAESA-CORTAILLOD, SWITZERLAND

Contact: B. Dardel. AESA, Plaine 7, CH-2013 Colombier, Tel: +41 32 843 03 99, Mobile: +41 79 477 05 09, [email protected]


Introduction

Metallic conductors are usually the main source of cost in a cable

• High density and cost of metal as compared to plastic material

Reducing these costs allows to save a large amount of money

Trend : aluminum replaces copper.

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DESIGNimprovement

targetingLIMIT

subsequentSAVINGS


Main Standards

IEC 60228 (“Conductors of insulated cables” )

• Min Number (class 2) / Max diameter (Class 5/6) of wires

• Linear electrical resistance: Measured

ASTM Standards B8-11 (“Standard Specification for Concentric Lay-Stranded Copper conductors” - respectively B231/B231M-12 for aluminium)• Wire number/dimension/lay length

• Conductor diameter

• Area: Calculated from wire dimensions or measured by weight• Linear resistance: Calculated from area and material

resistivity or measured

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Determination of conductor area (ASTM)

𝑨𝟏𝑲

𝑾𝑳 𝒇

where A = Conductor area

K = Correction factor for the wires overlengths due to stranding

𝐾 1𝑘100

with k = Increment of mass or electrical resistance

W = Mass of the sample

L = Length of the sample

f = Mass factor of the material (density)8.890g/cm3 for Copper and 2.705g/cm3 for Aluminum 1350 at 20°C

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By weight

Cut the conductor

Weight sample

Measure sample lengthCalculate from design


Determination of conductor area (ASTM)

Uncertainty

K = 0.16% (deviation of the lay length of 0.01 x diameter of the layer)W = 0.1% (as prescribed in the standard)L = 0.13% (square distribution of +/- 1/32 inch over 2 feet)f = Negligible

A = 0.23%

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Determination of Linear resistance (ASTM)

𝑹𝑲 𝝆𝑨 𝑲

𝟐 𝑳 𝒇 𝝆𝑾

where R = Linear resistance𝝆 = Resistivity of the material

0.017241 mm2/m for 100%IACS at 20°C

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Considering the uncertainty on the resistivity given in ASTM B193-02

= 0.3%

R = 0.41%

By area and resistivity

Measure area

Measure sample resistance


Typical distribution

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= 0.4%

/500MCM


What about linear resistance measurement ?

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On-the-line measurement: principle

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𝑹𝑼𝑰

𝜌 𝜌 1 𝛼 𝑇 𝑇where = Resistivity

T = Measurement temperatureT0 = 20°C = Reference temperature = Temperature coefficient of the resistivity

0.393% for Copper and 0.403% for Aluminum


On-the-line measurement: Practically

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On-the-line measurement: Practically

• Measurement at 2.5 Hz converted to DC (Synchronous rectifiers)

Allows to measure and control the current in conductor• Temperature stabilization: sensors + heaters

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On-the-line measurement: Performances

Measurement precision is • Copper conductors:

• 0.1% up to 1000mm2/2000MCM• 0.2% up to 1800mm2/3600MCM

• Aluminium conductors:• 0.1% up to 300mm2/600MCM• 0.2% up to 1200mm2/2400MCM

When using the heating system, these values may slightly increase, depending on the selected stabilization parameters

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Comparison

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Comparison Weighting method Resistance measurement

Precision > 0.4% 0.1 - 0.2%

Need to cut the conductor Yes No

Dependent on material conductivity Yes No

Dependent on material density Yes No

Depending on stranding accuracy Yes No

Quick and easy No Yes


Relevance of the precision

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Gaussian distribution


Relevance of the precision

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1

3

15.9%

0.1%

Savings

0.3%

0.9%


Conclusion

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On-the-line linear resistance measurements• Improves the efficiency of design validation and process

controls, integrating the effect of all the usually individually measured parameters.

• The measurement takes only few minutes directly on the production line without the need to cut the conductor.


Conclusion

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On-the-line linear resistance measurements• It can be repeated along the production for process control

or for design improvement.

• Permits a finer tuning of the conductor design, allowing material saving.

electrical linear resistance versus weight … · 2019. 8. 15. · astm standards b8-11...

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