Electric Winding Shield Layer for Partial Discharge Insulation
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Solution Overview
Problem
Conventional electric machines, particularly those used in aircraft, face limitations in power density and temperature ratings due to susceptibility to partial discharges at high altitudes, which are exacerbated by lower partial discharge inception and extinction voltages, and existing insulation methods either reduce space or limit operational temperature and power ratings.
Innovation Solution
The implementation of a conductor core with an insulation layer surrounded by a conductive shield layer, featuring an insulative carrier with a thermal rating greater than 180°C and a conductive layer with a surface resistivity between 1.5 and 10 ohms per square, which prevents partial discharges without increasing insulation thickness, thereby enhancing operational temperature and electrical ratings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional insulation methods are used, then insulation is provided, but space is reduced and operational temperature and power ratings are limited
Solution Approach 1:
The patent applies composite materials by combining an insulating layer with a conductive shield layer having specific surface resistivity (10^-6 to 10^6 ohms per square). This composite structure provides both insulation and partial discharge prevention functions, eliminating the need for additional space-consuming insulation while maintaining reliability at elevated temperatures and power ratings.
2Reliability
If insulation thickness is increased to prevent partial discharges, then reliability improves, but machine size increases
Solution Approach 1:
The patent changes the electrical parameter of the insulation system by introducing a conductive shield layer with controlled surface resistivity (10^-6 to 10^6 ohms per square). This parameter modification enables the thin insulation structure to prevent partial discharges through electrostatic field redistribution, achieving reliability without increasing machine size.
Solution Approach 2:
The conductive shield layer acts as an intermediary between the insulating layer and the external environment. It mediates the electrostatic field by redistributing charges on its surface, preventing field concentration that would lead to partial discharges, thereby protecting the insulation without requiring increased thickness.
3Power
If operational temperature is increased to improve power density, then power rating improves, but risk of partial discharges increases
Solution Approach 1:
The conductive shield layer serves as a thermal and electrical intermediary that stabilizes the electrostatic field environment. By maintaining controlled surface resistivity across temperature ranges, it prevents thermal runaway and partial discharge initiation, enabling safe operation at elevated temperatures for improved power density.
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 allows for higher voltage operation at sea level and cruise altitudes without increasing machine size, improving power density and temperature ratings while reducing the risk of partial discharges.
Implementation Method 1
a conductive layer having a surface resistivity between 1.5 and 10 ohms per square disposed on the insulative carrier
Implementation Method 2
prevents partial discharges without increasing insulation thickness
Data Source
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AI summary
An electric winding assembly (100), (200), includes a conductor core (108) having a first end (110) and an opposing second end (112), an insulation layer (114) overlying the conductor core (108), and a conductive shield layer (116) overlying the insulation layer (114). The conductive shield layer (116) includes an insulative carrier (117) circumferentially surrounding the insulation layer (114) and a conductive layer (118) disposed on the insulative carrier (117), the insulative carrier (117) formed from a material having a thermal rating greater than 180°C, the conductive shield layer (116) having a surface resistivity between 1.5 and 10 ohms per square.