Stator Bilayer Insulation for Rotating Machine Thermal Stress
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing stator windings in rotating electric machines are prone to insulation failure due to damage from bending processes and high temperature environments, where the insulative coating is susceptible to damage from mechanical stress and thermal expansion differences between the coating and conductor materials.
Innovation Solution
A stator design featuring a bilayer insulative coating with a protective layer having a Young's modulus greater than the insulating layer at room temperature and less than at high temperatures, which prevents damage during bending and thermal expansion, ensuring the insulating layer remains intact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the insulative coating is made thin to reduce size, then the manufacturing precision is improved, but the insulation reliability deteriorates due to increased susceptibility to damage from bending and thermal expansion
Solution Approach 1:
The insulative coating is divided into two distinct layers: an inner insulating layer in direct contact with the conductor, and an outer protective layer with different mechanical properties. This segmentation allows each layer to perform its specific function - the insulating layer provides electrical insulation while the protective layer resists mechanical damage from bending and thermal expansion, thereby maintaining reliability even when the total coating thickness is reduced.
Solution Approach 2:
The coating uses composite material structure with two layers having different Young's moduli. The inner insulating layer has higher Young's modulus for dimensional stability, while the outer protective layer has lower Young's modulus to absorb mechanical stress during bending and thermal cycling. This composite approach enables thin coating design without compromising insulation reliability.
2Strength
If the Young's modulus of the insulative coating is increased to improve mechanical strength, then the strength is improved, but the reliability deteriorates due to increased thermal expansion stress at high temperatures
Solution Approach 1:
Different regions of the coating have different mechanical properties tailored to their specific functions. The inner insulating layer has higher Young's modulus to maintain dimensional stability and provide effective insulation, while the outer protective layer has lower Young's modulus specifically at high temperatures to reduce thermal expansion stress. This local differentiation of material properties resolves the contradiction between mechanical strength and thermal stress resistance.
Solution Approach 2:
The Young's modulus of the protective layer is designed to change with temperature - having higher value at room temperature for mechanical protection during handling and bending, and lower value at high temperatures to reduce thermal expansion stress. This temperature-dependent parameter change allows the coating to adapt to different operating conditions, maintaining reliability across the temperature range.
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 solution effectively prevents insulation failure by allowing the protective layer to absorb mechanical stress and reduce thermal expansion stress, maintaining the integrity of the insulating layer and ensuring reliable electrical insulation.
Implementation Method 1
The protective layer is formed of a material having a Young's modulus that is equal to or greater than a Young's modulus of the insulating layer at room temperature... the protective layer to absorb mechanical stress
Implementation Method 2
Elevated temperature of the stator winding may cause the insulative coating of each U-shaped conductor segment to thermally expand. The insulative coatings of slot-received portions of the U-shaped conductor segment are prone to be damaged or collapsed within the slots of the stator core under stress due to a difference in the coefficient of thermal expansion between the insulative coating and the conductor
Data Source
AI summary
A stator for a rotating electric machine, including an annular stator core having a plurality of slots circumferentially arranged in the stator core, and a stator winding wound around the stator core and comprised of a plurality of U-shaped conductor segments inserted in the slots and connected to each other. Each conductor segment includes a conductor and a bilayer insulative coating comprised of an insulating layer covering a peripheral surface of the conductor and a protective layer covering a peripheral surface of the insulating layer. The protective layer is formed of a material having a Young's modulus that is equal to or greater than a Young's modulus of the insulating layer at room temperature and less than the Young's modulus of the insulating layer in high temperature environments caused by heat generation of the stator winding.