Polyamide-imide Varnish for Motor Coils Reducing Permittivity

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Solution Overview

Problem

Polyamide-imide resin insulating varnishes used in enameled wires for motor coils face challenges with high permittivity, leading to low partial discharge inception voltage, which is exacerbated by high voltage driving and inverter surge, compromising insulation and increasing the risk of partial discharge and short-circuit risks due to low softening resistant temperature.

Innovation Solution

A polyamide-imide resin insulating varnish is developed comprising an aromatic diamine component with three or more benzene rings and an aromatic diamine with two or less benzene rings, along with an aromatic diisocyanate and acid components, to reduce permittivity while maintaining heat resistance and mechanical performance, achieving a specific permittivity of not more than 3.5 by adjusting the mole ratio and using specific monomers like 2,2-bis[4-(4-aminophenoxy)phenyl]propane and 4,4′-diaminodiphenylether.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If polyamide-imide resin insulating varnish is used for enameled wires, then heat resistance, mechanical performance, and hydrolysis resistance are improved, but permittivity increases leading to low partial discharge inception voltage

Engineering Contradiction:

Improveheat resistance, mechanical performance, hydrolysis resistanceVSAvoidpartial discharge inception voltage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the chemical composition parameters of the diamine component by specifying particular aromatic diamines with defined structures (Formula 1) and molar ratios, thereby reducing the permittivity of the polyamide-imide resin from conventional high values to ≤3.5 while preserving heat resistance and mechanical performance

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite resin system by combining polyamide-imide resin with specific diamine components having particular molecular structures, forming a new material composition that achieves both low permittivity and high reliability properties simultaneously

Inventive Principle:

Principle #40Composite materials

2Strength

If conventional polyamide-imide resin is used, then excellent mechanical performance and hydrolysis resistance are achieved, but softening resistant temperature is low increasing short-circuit risk

Engineering Contradiction:

Improvemechanical performance, hydrolysis resistanceVSAvoidsoftening resistant temperature

Core Design Contradiction:

StrengthVSTemperature

Solution Approach 1:

The patent modifies the resin's thermal parameters by selecting specific aromatic diamines with particular molecular structures and controlling their molar ratios in the polymerization, thereby elevating the softening resistant temperature to 390°C or higher while preserving mechanical strength and hydrolysis resistance

Inventive Principle:

Principle #35Parameter changes

3Power

If motor drive voltage is increased for high efficiency, then power output is improved, but partial discharge risk increases due to inverter surge

Engineering Contradiction:

Improvepower outputVSAvoidpartial discharge risk

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The patent changes the electrical parameters of the insulating varnish by reducing permittivity through specific diamine component selection, thereby increasing partial discharge inception voltage to enable safe operation at higher drive voltages with inverter surge conditions

Inventive Principle:

Principle #35Parameter changes

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 varnish effectively reduces permittivity, enhancing partial discharge resistance and maintaining heat resistance, mechanical performance, and oil resistance, thereby improving the partial discharge inception voltage and reducing the risk of insulation breakdown and short-circuits under high temperature conditions.

Implementation Method 1

two components of 4,4′-diphenylmethanediisocyanate (MDI) and trimellitic anhydride (TMA) are mainly reacted by decarboxylation reaction

Methodology Applied

Scientific EffectDecarboxylation reaction:

Implementation Method 2

One of the drawbacks of the covering of polyamide-imide resin insulating varnish is its high permittivity... if the polyamide-imide resin insulating varnish could have a low permittivity, an enameled wire excellent in partial discharge resistance can be realized

Methodology Applied

Scientific EffectPermittivity reduction: Dielectric Permittivity

Data Source

PatentUS8193451B2Polyamide-imide resin insulating varnish and insulated wire using the same

Publication Date: 2012.06.05 HITACHI MAGNET WIRE CORP

AI summary

A polyamide-imide resin insulating varnish includes an aromatic diamine component, an aromatic diisocyanate component, an acid component including an aromatic tricarboxylic acid anhydride, and a solvent. The aromatic diamine component includes an aromatic diamine with three or more benzene rings and an aromatic diamine with two or less benzene rings. The aromatic diamine with three or more benzene rings and the aromatic diamine with two or less benzene rings are added 99/1 to 30/70 in mole ratio.