Post on 31-Jan-2021
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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, bdardel@aesa-cortaillod.com
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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
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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
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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
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Typical distribution
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= 0.4%
/500MCM
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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
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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
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Relevance of the precision
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Gaussian distribution
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Relevance of the precision
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1
3
15.9%
0.1%
Savings
0.3%
0.9%
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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.
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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.