Insulating Material for Coil with Differential Foaming
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Solution Overview
Problem
The existing insulating materials for coils in rotary electric machines face issues with inconsistent foaming rates between the coil-side and stator-core-side expansive additive layers due to temperature differences, leading to insufficient fixing force and potential excessive foaming, which affects the retentivity of the coil.
Innovation Solution
The insulating material includes a stator-core-side expansive additive layer with a foam material that starts foaming at a lower temperature and has a shifted foaming rate increase characteristic to the cold side, matching the foaming characteristic of the coil-side expansive additive layer, ensuring both layers foam at a similar rate despite temperature differences between the coil and stator core.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single foam material is used for both coil-side and stator-core-side expansive additive layers, then the manufacturing process is simplified, but the foaming rates become ununiform due to temperature differences, leading to excessive foaming on the coil side and insufficient fixing force
Solution Approach 1:
The patent applies local quality by selecting different foam materials with different foaming characteristics for the coil-side and stator-core-side expansive additive layers. The coil-side layer uses a foam material with lower foaming activity to prevent excessive foaming, while the stator-core-side layer uses a foam material with higher foaming activity to ensure adequate expansion despite lower temperatures. This localized differentiation resolves the contradiction between manufacturing simplicity and foaming uniformity.
Solution Approach 2:
The patent changes the parameters of the foam materials used in the expansive additive layers. Specifically, it selects foam materials with different foaming starting temperatures, peak temperatures, and foaming rates. By adjusting these parameters according to the thermal characteristics of each location (coil side vs. stator core side), the patent achieves uniform foaming behavior across both sides while maintaining a relatively simple manufacturing process.
2Temperature
If the stator core is heated to the peak temperature Tp, then the foaming process is completed, but the temperature difference between the coil and stator core causes delayed temperature rise of the stator core, resulting in delayed foaming of the stator-core-side expansive additive layer
Solution Approach 1:
The patent changes the thermal parameters of the foam materials to compensate for the time delay in stator core heating. By selecting a foam material for the stator-core-side layer with a lower foaming starting temperature and earlier peak temperature, the patent ensures that this layer begins foaming sooner and completes its expansion before the coil-side layer, thereby compensating for the delayed heat transfer to the stator core.
Solution Approach 2:
The patent applies preliminary action by designing the stator-core-side expansive additive layer to begin foaming earlier than the coil-side layer. This is achieved by selecting a foam material with lower thermal activation requirements, so that the stator-core-side layer starts expanding while the stator core is still heating up, rather than waiting for the stator core to reach its final temperature.
3Productivity
If the coil-side expansive additive layer expands ahead of the stator-core-side layer, then the gap filling is accelerated, but excessive foaming occurs on the coil side, increasing porosity and decreasing retentivity
Solution Approach 1:
The patent applies local quality by differentiating the foaming characteristics of the expansive additive layers on different sides. The coil-side layer uses a foam material with lower foaming activity and later peak temperature to prevent excessive expansion, while the stator-core-side layer uses a foam material with higher foaming activity to ensure adequate gap filling. This localized differentiation maintains both gap filling efficiency and coil retentivity.
Solution Approach 2:
The patent applies preliminary anti-action by pre-selecting foam materials with appropriate foaming characteristics to counteract the tendency toward excessive foaming on the coil side. By choosing a foam material with lower foaming activity for the coil-side layer, the patent prevents overexpansion before it occurs, thereby maintaining the density and retentivity of the expansive additive layer while still achieving adequate gap filling.
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 approach reduces the difference in foaming rates between the coil-side and stator-core-side expansive additive layers, maintaining consistent expansion and preventing excessive foaming, thereby ensuring sufficient retentivity and fixing force for the coil.
Implementation Method 1
a foam material included in the expansive additive layer foams and expands
Implementation Method 2
When a stator assembly configured such that the insulating material and the coil are assembled to the stator core is heated in a heating furnace and the like, a foam material included in the expansive additive layer foams and expands
Implementation Method 3
Due to an expansion pressure at this time and an adhesive included in the expansive additive layer, the coil is fixed to the stator core
Data Source
AI summary
A stator-core-side expansive additive layer and a coil-side expansive additive layer include foam materials foaming by heating. A foam material included in the stator-core-side expansive additive layer has such a foaming characteristic that an increase characteristic of a foaming rate along with a temperature rise is shifted to a cold side relative to the increase characteristic of a foam material included in the coil-side expansive additive layer.