Armoured AC Cable Armour Winding Pitch Optimization
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Solution Overview
Problem
Existing methods for calculating the permissible current rating of armoured AC cables overestimate armour losses, leading to inefficiencies in current transmission and conductor sizing, as current standards like IEC 60287-1-1 do not accurately account for the effects of armour winding pitch on power losses.
Innovation Solution
The method involves using an armoured AC cable with an armour winding pitch that is unilay to the core stranding pitch, within a specific range (0.4A to 2.5A), to reduce armour losses to less than 30% of overall cable losses, thereby increasing the permissible current rating and allowing for reduced conductor cross-section areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If standard IEC 60287-1-1 calculation methods are used for armoured AC cables, then current rating is conservatively determined, but armour losses are overestimated leading to reduced current transmission efficiency
Solution Approach 1:
The patent changes the geometric parameter of the armour winding pitch to reduce armour losses. By optimizing the pitch within the range of 0.4A to 2.5A (where A is the core stranding pitch), the magnetic coupling between armour wires is minimized, reducing eddy current losses and hysteresis effects, thereby improving current transmission efficiency while maintaining mechanical protection
2Strength
If conventional armour configuration is used, then cable mechanical strength is maintained, but conductor cross-section must be larger to compensate for armour losses
Solution Approach 1:
The patent optimizes the armour winding pitch parameter to reduce energy losses in the armour layer. This allows the same current rating to be achieved with smaller conductor cross-sections, or alternatively, enables the use of smaller conductors while maintaining the same current capacity, thus reducing the quantity of conductive material required
3Productivity
If armour winding pitch is optimized to reduce losses, then current rating increases, but armour geometry becomes more complex
Solution Approach 1:
The patent defines a specific range for the armour winding pitch (0.4A to 2.5A times the core stranding pitch) that balances loss reduction with manufacturing feasibility. This parameter optimization achieves up to 30% reduction in armour losses compared to conventional configurations, increasing permissible current rating while maintaining practical armour geometry for standard manufacturing processes
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration reduces armour losses, allowing for higher current transmission and smaller conductor sizes while maintaining the cable's integrity, improving the cable's performance and efficiency in compliance with IEC standards.
Implementation Method 1
the ratio λ2 is given, in IEC 60287-1-1, by the following formula: λ2=RA/(nR)×(dA/2c)2×f where RA is the AC resistance of armour at maximum armour temperature
Implementation Method 2
an armour surrounding the at least two cores, said armour comprising one layer of a plurality of metal wires wound around the cores according to a helical, armour winding lay and an armour winding pitch B
Implementation Method 3
When alternate current (AC) is transported into a cable, the temperature of electric conductors within, the cable rises due to resistive losses, a phenomenon referred to as Joule effect
Data Source
AI summary
An armored cable for transporting an alternate current at a maximum allowable working conductor temperature includes: at least two cores stranded together according to a core stranding lay and a core stranding pitch A; and an armor surrounding the at least two cores, the armor including one layer of a plurality of metal wires wound around the cores according to a helical armor winding lay and an armor winding pitch B, the helical armor winding lay having the same direction as the core stranding lay, the armor winding pitch B being from 0.4A to 2.5A and differing from the core stranding pitch A by at least 10%.