Flexible Electrical Lead Thermal Isolation for Motor Controllers
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Solution Overview
Problem
The existing motor controllers for aircraft electric starter motors face a challenge in managing heat transfer from high-current bus bars to thermally sensitive capacitors, which can exceed the capacitors' maximum temperature capacity due to direct thermal conduction.
Innovation Solution
A flexible electrical lead with a conductive trace covered in insulating material is used to connect capacitors to bus bars, featuring a second cross-sectional area that is 2.5% or less than the bus bar's, effectively thermally isolating the capacitors from the heat conducted by the bus bars.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bus bar is secured directly to the printed wiring board, then electrical continuity is provided, but significant heat is transmitted from the bus bar to the capacitors causing them to operate beyond their maximum temperature limit
Solution Approach 1:
A flexible electrical lead with small cross-sectional area is introduced as an intermediary component between the bus bar and the printed wiring board. This lead provides electrical continuity while its small cross-section limits thermal conduction, preventing excessive heat transfer to the capacitors.
Solution Approach 2:
The electrical lead has different cross-sectional areas at different locations: a small cross-sectional area in the portion connecting to the printed wiring board (for thermal isolation) and a larger cross-sectional area at the bus bar connection (for adequate current carrying capacity). This local variation in geometry resolves the contradiction between electrical continuity and thermal isolation.
2Temperature
If a flexible electrical lead with small cross-sectional area is used to connect the capacitor to the bus bar, then thermal isolation is achieved, but the current carrying capacity may be limited
Solution Approach 1:
The electrical lead features non-uniform cross-sectional area along its length. The portion adjacent to the bus bar has a larger cross-sectional area to handle high current density and minimize resistive heating at the connection point, while the portion adjacent to the printed wiring board has a smaller cross-sectional area to limit thermal conduction to the capacitors. This local differentiation allows the single component to satisfy both contradictory requirements.
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 solution prevents significant heat transfer from the bus bars to the capacitors, ensuring they operate within their safe temperature limits and maintaining electrical continuity while reducing thermal stress.
Implementation Method 1
a significant amount of heat is transmitted from the bus bar to the PWB and the capacitors
Implementation Method 2
The flexible electrical lead includes a conductive trace covered in an insulating material
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3
AI summary
An electrical assembly for a motor controller (31) is disclosed that includes an electrical lead (34). The electrical lead has a conductive trace within an insulating material and that extends a length between first and second ends. An electrical pad is in electrical continuity with and extends from the conductive trace through the insulating material at the first end. The pad includes an aperture providing a securing feature. An electrical component (32) is supported by and integral with the second end, in one example. The electrical component is in electrical continuity with the conductive trace at the second end. A bus bar (22) provides a joint having a first cross-sectional area. The electrical lead is flexible and is removably secured to the joint by the securing feature to provide electrical continuity from a capacitor to the bus bar. The flexible electrical lead has a second cross-sectional area substantially less than the first cross-sectional area.