Polyimide Insulation Film for Rectangular Conductors
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Solution Overview
Problem
Insulated electric wires with high partial discharge inception voltage (PDIV) face challenges in cost reduction due to the need for interphase insulating papers, and when thickened over rectangular conductors, they tend to crack due to non-uniform film thickness and reduced heat resistance.
Innovation Solution
The development of an insulated electric wire with an insulation film having a peak loss tangent tan δ value less than 1.0, achieved by using a polyimide resin with specific diamine and dianhydride components, ensures uniform film thickness and enhanced flexibility, even when thickened over rectangular conductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the insulation film is thickened to prevent dielectric breakdown and enhance PDIV, then the insulation performance is improved, but the film cracks during molding due to non-uniform thickness and reduced flexibility
Solution Approach 1:
The patent changes the chemical composition parameters of the polyimide resin by controlling the imide group concentration within 15-20% and using specific raw material ratios (BPADA:diamine = 0.95:1 to 1.05:1). These parameter changes optimize the balance between film thickness, uniformity, and flexibility, preventing crack formation during molding while maintaining high insulation performance and PDIV.
Solution Approach 2:
The patent creates a composite insulation film system by combining polyimide resin with specific additives and controlling the imidization process to achieve a heterogeneous structure with optimal properties. The composite nature of the film, with controlled imide group distribution, provides both the thickness needed for high PDIV and the flexibility needed to prevent cracking during coil molding.
2Reliability
If interphase insulating papers are inserted to prevent dielectric breakdown, then the insulation reliability is improved, but the manufacturing time and cost increase
Solution Approach 1:
The patent merges the functions of multiple separate insulating components (interphase insulating papers and insulation films) into a single integrated insulation film structure. By controlling the polyimide resin composition and imidization process, the film achieves both high PDIV and sufficient mechanical strength to replace the need for additional insulating papers, thereby simplifying the motor production process and improving manufacturing efficiency.
Solution Approach 2:
The patent creates a universal insulation film that performs multiple functions simultaneously: providing high dielectric strength for PDIV enhancement, ensuring mechanical flexibility for molding, and eliminating the need for separate interphase insulating papers. This multi-functional film reduces both manufacturing complexity and cost while maintaining insulation reliability.
3Reliability
If the dielectric constant of the insulation film is lowered to enhance PDIV, then the partial discharge resistance is improved, but the heat resistance and film uniformity deteriorate
Solution Approach 1:
The patent optimizes the dielectric constant parameter by controlling the imide group concentration at 15-20% and adjusting the raw material ratio. This parameter optimization achieves the right balance: the dielectric constant is sufficiently low to enhance PDIV, while the film maintains uniform thickness distribution and adequate heat resistance through the controlled chemical composition and imidization process.
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
The solution provides an insulated electric wire with superior flexibility and heat resistance, preventing crack formation and maintaining high PDIV, thus enabling cost-effective production and reliable performance in motor coils.
Implementation Method 1
the insulation film is essentially consisted of a resin including an imide structure in a molecule, and has a peak value of a loss tangent tan δ represented by a loss elastic modulus to storage elastic modulus ratio when measured in a range of 50 degrees C to 400 degrees C is smaller than 1.0
Data Source
Figure 1~2
AI summary
Provided are an insulated electric wire having excellent flexibility even when the thickness of an insulation film over a rectangular conductor is increased, and a coil using this insulated electric wire. The insulated electric wire (1) comprises a rectangular conductor (10) and an insulation film (11) disposed on the periphery of the rectangular conductor (10). The insulation film (11) is characterized by: the provision of a resin containing an imide structure within a molecule; and a peak value of less than 1.0 for the loss tangent tan δ, which is represented by the ratio between the loss elastic modulus and the storage elastic modulus, as measured in the 50 DEG C to 400 DEG C range.