Insulated Wire Outer Diameter Reduction via Layered Resistivity
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Solution Overview
Problem
Existing insulated wires face challenges in reducing their outer diameter while maintaining high insulation and flame-retardant properties, as conventional approaches often compromise either the insulation or flame-retardant properties when trying to minimize the wire's thickness.
Innovation Solution
The insulated wire structure comprises a conductor with a semiconductive layer, an insulating layer, and a flame-retardant semiconductive layer, where the semiconductive layer has a volume resistivity of ≤1.5×10^15 Ωcm, the insulating layer ≥5.0×10^15 Ωcm, and the flame-retardant semiconductive layer has an oxygen index >40, allowing for a thinner coating layer and reduced outer diameter while passing vertical tray flame and direct-current stability tests.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the thickness of the coating layer is reduced to decrease the outer diameter of the insulated wire, then the outer diameter is reduced, but the insulation property and flame-retardant property deteriorate
Solution Approach 1:
The coating layer is divided into three distinct functional layers: an inner semiconductive layer for electrical field control, a middle insulating layer for electrical insulation, and an outer flame-retardant semiconductive layer for flame resistance and electrostatic control. This segmentation allows each layer to be optimized for its specific function, enabling reduced overall thickness while maintaining all required properties.
Solution Approach 2:
The patent uses composite material compositions in each layer, particularly in the flame-retardant semiconductive layer which combines flame-retardant resins (such as polypropylene with flame retardants) with semiconductive fillers. This composite approach allows simultaneous achievement of flame retardancy (oxygen index >40) and semiconductivity (volume resistivity ≤1.5×10^15 Ωcm) in a thin layer.
2Reliability
If a flame-retardant layer is added on the outer periphery of the insulating layer, then the flame-retardant property is improved, but the outer diameter increases
Solution Approach 1:
The outer flame-retardant semiconductive layer performs multiple functions simultaneously: it provides flame retardancy (achieving oxygen index >40), maintains semiconductivity for electrostatic control (volume resistivity ≤1.5×10^15 Ωcm), and protects the insulating layer. This multi-functionality eliminates the need for separate layers, reducing overall thickness while maintaining all required properties.
Solution Approach 2:
The patent changes the material parameters of the outer layer to achieve both flame retardancy and semiconductivity. By selecting flame-retardant resins with appropriate semiconductive fillers and controlling the volume resistivity to be ≤1.5×10^15 Ωcm and oxygen index to be >40, the layer achieves dual functionality at reduced thickness.
3Length of stationary object
If the thickness of the insulating layer is reduced to decrease the outer diameter, then the outer diameter is reduced, but the insulation property deteriorates
Solution Approach 1:
The inner semiconductive layer is provided beforehand to control the electrostatic field and prevent field concentration at the conductor surface. This protective layer prevents electrical breakdown, allowing the insulating layer to be thinner while maintaining insulation reliability. The semiconductive layer acts as a cushion against electrical stress.
Solution Approach 2:
The insulating layer uses high-performance insulating resin compositions with optimized molecular structures and additives to achieve maximum insulation properties (volume resistivity >5.0×10^15 Ωcm) at minimal thickness. The composite material approach allows superior insulation performance in a thin layer.
Data Source
AI summary
An insulated wire having an electrical wire structure capable of reducing an outer diameter while an insulation property and a flame-retardant property are highly kept is provided. In the insulated wire including: a conductor; and a coating layer arranged on an outer periphery of the conductor, the coating layer includes: a semiconductive layer having a volume resistivity defined by JIS C2151 that is equal to or smaller than 1.0×1015 (Ωcm); an insulating layer arranged on an outer periphery of the semiconductive layer, the insulating layer having a volume resistivity defined by JIS C2151 that is larger than 5.0×1015 (Ωcm); and a flame-retardant semiconductive layer arranged on an outer periphery of the insulating layer, the flame-retardant semiconductive layer having a volume resistivity defined by JIS C2151 that is equal to or smaller than 1.5×1015 (Ωcm) and having an oxygen index defined by JIS K7201-2 that is larger than 40.