Stator Insulation Segmentation for Thermal Stress Relief
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional stators for electric rotating machines experience insulator cracking and peeling due to thermal expansion and stress concentration, particularly at the conductor-joining portions, leading to potential failure of the stator winding.
Innovation Solution
The stator design incorporates a low-adhesion portion on the insulation cover, positioned away from the end portion, which absorbs size changes and reduces shear stress, while an adhesion portion with higher adhesive strength maintains pulling residual stress, thereby preventing insulator cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the insulation cover is fully adhered to the conductor throughout its length, then the insulation cover provides continuous protection and support, but thermal expansion and contraction cause stress concentration at the end portion, leading to insulator cracking and peeling
Solution Approach 1:
The adhesion between the insulation cover and conductor is segmented into two distinct zones: a first adhesion portion with strong bonding and a second adhesion portion with reduced bonding. This segmentation allows the insulation cover to maintain protection where needed while reducing stress concentration at the end portion, preventing cracking and peeling during thermal cycles.
Solution Approach 2:
Different adhesion characteristics are applied to different portions of the insulation cover-conductor interface. The first adhesion portion maintains full adhesion for structural support and protection, while the second adhesion portion at the end has reduced adhesion to accommodate thermal expansion and contraction, eliminating the harmful stress concentration that causes cracking.
2Strength
If the insulation cover is made more rigid to maintain structural integrity, then the insulation cover provides better support, but it becomes more susceptible to cracking under thermal stress
Solution Approach 1:
The adhesion interface is divided into segments with different bonding characteristics. The first adhesion portion provides strong bonding for structural integrity, while the second adhesion portion allows controlled movement to accommodate thermal expansion, preventing crack propagation in the rigid insulation cover material.
3Strength
If the adhesive strength is increased throughout the entire insulation cover, then the insulation cover remains firmly attached, but thermal expansion causes greater shear stress at the end portion, leading to cracking
Solution Approach 1:
The adhesive strength is made non-uniform along the length of the insulation cover. The first adhesion portion has high adhesive strength for firm attachment, while the second adhesion portion at the end has reduced adhesive strength to minimize shear stress concentration during thermal expansion, preventing cracking.
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 configuration effectively suppresses insulator cracking and peeling, ensuring the stator winding's integrity and reliability under temperature fluctuations.
Implementation Method 1
cracking of the insulator of the conductor-joining portion may occur around an end portion of the insulation cover layer provided on the conductor segment... caused by a difference in a linear expansion co-efficient between the insulation cover of the conductor segment and the insulator that covers the conductor-joining portion
Data Source
AI summary
A stator for a rotating electric machine has a stator core provided with a plurality of slots arranged in a circumferential direction of the stator core, and a stator winding that is wound around the slots. The stator winding is configured of a plurality of covered conductor linear portions. The covered conductor linear portions are each provided with an exposed portion formed on an end. The plurality of covered conductor linear portions are each joined to another covered conductor linear portion at the exposed portion, and the conductor joined portion is covered by an insulator at least in a range that includes an end portion of the insulation cover. The insulation cover covers the conductor, in an adhered state there to, and has a low-adhesion portion that that is either adhesive-free or has a lower adhesive strength than other parts on the conductor and is distanced from an end portion.