What causes cable sheath cracking after a few years of outdoor use?
UV radiation (PVC not UV-stable)
Low-temperature embrittlement (PVC brittle below -15°C)
Thermo-oxidative ageing
Plasticizer migration (moisture or chemicals)
Mechanical stress (tight bending or tension)
Solution: use weather-resistant materials (XLPE, TPU, PE, or weather-resistant PVC).
Source: Polymer ageing studies.
How much larger should aluminum cable be compared to copper for the same ampacity?
Aluminum conductivity ≈ 61% of copper (IACS). For same ampacity, aluminum cross-section ≈ 1.6× copper.
Example: copper 10mm² → aluminum 16mm².
Note: Voltage drop is higher; termination must be bi-metallic to avoid oxidation and creep.
Source: IACS standard & engineering practice.
What is a drain wire? What is its purpose?
A drain wire (bare or tinned copper) runs longitudinally inside or alongside the shield (braid or foil).
Functions:
1) Lowers shield contact resistance for easy grounding
2) Simplifies termination
3) Ensures shield continuity for better EMI rejection
Common in instrumentation, RS-485, audio cables.
Source: EMC design guide.
How to claim if cable length is found insufficient upon arrival?
1.Keep original packaging and meter markings, take photos/videos.
2.Measure at least 3 reels with a length counter.
3.Contact supplier with evidence.
4.Claim per contract (typically double compensation or replacement).
Specify tolerance (e.g., -0%/+5%) and claim procedure in contract.
Source: Trade contract practices.
What are the responsibilities of buyer and seller under FOB vs CIF?
FOB: Seller loads goods onto vessel and handles export customs; buyer pays freight and insurance.
CIF: Seller pays freight and minimum insurance; risk transfers when goods pass ship's rail.
FOB is common for cable exports.
Source: Incoterms 2020.
What is the average sea freight time from China to US West Coast?
From major Chinese ports to Los Angeles/Long Beach: direct vessel about 14-18 days.
Door-to-door (including inland and customs): typically 25-35 days.
Subject to peak season, congestion, and carrier schedules.
Source: Shipping data & industry experience.
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