Polyimide Insulated Wire Partial Discharge Resistance
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Solution Overview
Problem
Insulated wires used in high-power motors face challenges with partial discharge inception voltage (PDIV) due to high relative permittivity of polyimide insulation layers, leading to potential insulation failure, and also suffer from mechanical weakness during high-temperature processes.
Innovation Solution
Incorporating 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA) into polyimide insulation layers, along with a specific molar ratio of diamine components, to reduce relative permittivity and enhance storage elastic modulus, thereby improving PDIV and high-temperature processability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the film thickness of the insulation layer is increased to improve PDIV, then partial discharge resistance is improved, but the space factor of the conductor decreases and the motor cannot output high power
Solution Approach 1:
The invention changes the physical and chemical parameters of the polyimide material by controlling the imide group concentration (0.45-0.55 mmol/cm³) and using specific raw materials with high molecular weight. This parameter optimization allows achieving high PDIV (≥900 Vp at 40 μm thickness) while maintaining thin film thickness, thus preserving conductor space factor and enabling high power output.
Solution Approach 2:
The invention uses composite polyimide structures formed from specific combinations of diamines (including ODA and at least one of TPE-Q, TPE-R, APB, BAPB, or BAPS) and dianhydrides (PMDA and/or s-BPDA). These composite material structures achieve optimal balance between electrical properties (low relative permittivity for high PDIV) and mechanical properties (adequate strength and flexibility), resolving the contradiction between insulation performance and space utilization.
2Reliability
If the imide group concentration in polyimide is reduced to decrease relative permittivity and improve PDIV, then partial discharge resistance is improved, but mechanical strength decreases and deformation occurs during high temperature process
Solution Approach 1:
The invention optimizes the imide group concentration parameter to a specific range (0.45-0.55 mmol/cm³) that balances electrical and mechanical properties. Additionally, it controls the molecular weight of raw materials (diamine ≥200, dianhydride ≥200) to ensure adequate mechanical strength while maintaining low relative permittivity. This dual parameter control achieves high PDIV without sacrificing mechanical integrity during high temperature processing.
Solution Approach 2:
The invention introduces specific diamine components (TPE-Q, TPE-R, APB, BAPB, or BAPS) with particular molecular structures that provide local structural reinforcement. These components contribute to maintaining mechanical strength in regions where the overall imide group concentration is reduced, thus preventing deformation during high temperature processes while still achieving low relative permittivity and high PDIV.
Data Source
AI summary
An insulated wire includes a conductor, and a polyimide insulation layer formed on an outer periphery of the conductor. The insulation layer includes a polyimide including a repeating unit represented by formula (1) and a repeating unit represented by formula (2). A first acid component in the repeating unit represented by the formula (1) and a second acid component in the repeating unit represented by the formula (2) are mixed in a molar ratio range of 85:15 to 40:60 as expressed by a molar ratio (the first acid component:the second acid component). R as a residue of a diamine component in the formulas (1) and (2) includes a residue of 4,4′-diaminodiphenyl ether and a residue of one selected from a group of diamines represented by the formulas (3) to (8). A storage elastic modulus of the polyimide at 325° C. is not less than 50 MPa.