Rotating Electric Machine Insulating Coat Crack Resistance
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Solution Overview
Problem
Existing rotating electric machines face issues with insulating coat punctures due to thermal stress, as the adhesion strength between varnish and insulating coats is higher than the tensile strength of the insulating coats, leading to cracks and potential breakdowns, especially when the machine is cooled rapidly.
Innovation Solution
The design features a stator coil with electric wire segments having insulating coats with a higher tensile strength than the adhesion strength between the insulating resin and the coats, preventing cracks from advancing to the conductors and ensuring the insulating coats are not punctured.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the adhesion strength between varnish and insulating coats is increased to ensure resistance to vibration, then the fixation of coil end parts is improved, but cracks will propagate to the insulating coats when thermal stress occurs, causing punctures
Solution Approach 1:
The patent changes the mechanical parameter (tensile strength) of the insulating coat material to be higher than the adhesion strength to the varnish. This parameter change ensures that when thermal stress causes the varnish to crack, the crack propagation is stopped at the varnish-insulating coat interface rather than penetrating into the insulating coat, thus resolving the contradiction between strong fixation and crack resistance
Solution Approach 2:
The patent applies the beforehand cushioning principle by designing the insulating coat with sufficient tensile strength to absorb and cushion the thermal stress before it can cause puncture. The insulating coat acts as a buffer that prevents the harmful effect of crack propagation from reaching the conductor, even though the varnish itself cracks under thermal stress
2Object-affected harmful factors
If the tensile strength of insulating coats is increased to prevent puncture, then the protection of electric conductors is improved, but the adhesion strength between varnish and insulating coats must be reduced, weakening the fixation
Solution Approach 1:
The patent applies parameter changes by selecting insulating coat materials with specifically controlled tensile strength values that are higher than the varnish adhesion strength. This creates an optimal balance where the insulating coat is strong enough to prevent puncture but not so strong that it creates excessive adhesion forces that would cause other problems. The parameter is precisely tuned to resolve the contradiction
Solution Approach 2:
The patent applies local quality by differentiating the mechanical properties at different locations and interfaces. The insulating coat has high tensile strength locally at the conductor interface to prevent puncture, while the adhesion interface with the varnish is designed with controlled strength to allow clean separation when thermal stress occurs. Each location has optimized properties for its specific function
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 effectively prevents punctures of the insulating coats by allowing cracks in the insulating resin to separate from the coats, thereby protecting the electric conductors and maintaining the integrity of the stator coil.
Implementation Method 1
the adhesion strength between the insulating resin and the insulating coats
Implementation Method 2
the insulating resin has a lower coefficient of linear expansion than the insulating coats... when operation of the rotating electric machine is stopped and thus the ambient temperature of the stator is changed from a high temperature to a low temperature, tensile stress will be induced in the insulating resin
Implementation Method 3
a tensile strength of the insulating coats of the electric wire segments is higher than an adhesion strength between the insulating resin and the insulating coats
Data Source
AI summary
A rotating electric machine includes a rotor, a stator and an Insulating resin. The stator includes a stator core and a stator coil that is partially received in slots of the stator core so as to have a pair of coil end parts protruding outside of the slots respectively on opposite axial sides of the stator core. The stator coil is formed of a plurality of electric wire segments, each of which includes an electric conductor and an Insulating coat that covers an outer surface of the electric conductor. The insulating resin is applied to the coil end parts of the stator coil so as to cover the outer surfaces of the insulating coats of the electric wire segments forming the stator coil. Further, a tensile strength of the insulating coats of the electric wire segments is higher than an adhesion strength between the insulating resin and the insulating coats.