Dielectric Plate Stator Slot Exit Surface Discharge Suppression
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Solution Overview
Problem
Electric machines operating at high altitudes and high voltages experience surface discharges on conductive windings due to low atmospheric pressure and increased electric fields, leading to insulation degradation and potential failure, as conventional insulation methods like corona protection and stress grading tapes are insufficient in preventing these discharges without generating excessive heat.
Innovation Solution
A stator assembly with dielectric plates coupled to slot exits of the stator core, reducing the electric field strength and suppressing surface discharges by using materials with a dielectric constant similar to the winding insulation, thereby preventing insulation degradation and extending the lifespan of the electric machine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If corona protection tape and stress grading tape are used to insulate windings, then insulation reliability is improved, but heat generation increases and may damage the insulation
Solution Approach 1:
The patent changes the material parameter (dielectric constant) of the insulation component at the slot exit by using a dielectric plate with a dielectric constant matching the winding insulation. This parameter change allows the electric field to be redistributed without concentrating it in the tape layers, thus preventing surface discharges while avoiding the heat generation problem associated with thicker conductive tapes
Solution Approach 2:
The dielectric plate acts as an intermediary component between the winding insulation and the air at the slot exit. It mediates the electric field distribution by providing a transition zone with appropriate dielectric properties, preventing direct exposure of the winding insulation to high electric fields without requiring thick conductive tapes that would generate excessive heat
2Reliability
If the thickness of corona protection tape and stress grading tape is increased to prevent surface discharges, then discharge suppression is improved, but heat generation increases and insulation damage occurs
Solution Approach 1:
The patent changes the dielectric parameter of the slot exit region by introducing a dielectric plate with a dielectric constant matched to the winding insulation. This parameter change enables effective discharge suppression through proper electric field distribution rather than through increased tape thickness, thereby avoiding the harmful heat generation effect
3Weight of moving object
If thin insulation is used around windings to reduce weight, then weight is reduced, but resistance to partial discharge decreases
Solution Approach 1:
The dielectric plate is installed at the slot exit before the winding insulation is exposed to high electric fields. This preliminary action creates a protective interface that prevents partial discharge from occurring at the vulnerable slot exit region, allowing thin insulation to be used elsewhere in the winding without compromising overall discharge resistance
Solution Approach 2:
The patent applies local quality enhancement by placing a dielectric plate specifically at the slot exit region where electric field concentration and partial discharge risk are highest. This localized protection allows thin insulation to be used in other areas to reduce weight, while maintaining high partial discharge resistance at the critical slot exit location
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 dielectric plates effectively reduce surface discharges and prevent insulation degradation, enabling electric machines to operate at high altitudes and voltages without failing, while also reducing the need for thick stress grading tapes and minimizing heat generation.
Implementation Method 1
A stator assembly with dielectric plates coupled to slot exits of the stator core, reducing the electric field strength and suppressing surface discharges by using materials with a dielectric constant similar to the winding insulation
Data Source
AI summary
A stator assembly of an electric machine includes a stator core having a slot extending between a first end and a second end, where the slot includes a first slot exit at the first end and a second slot exit at the second end. Also, the stator assembly includes a plurality of windings, where one of the plurality of windings is disposed in the slot and extends from the first slot exit to the second slot exit, and where the plurality of windings includes at least one conductor and an insulation disposed around the at least one conductor. Further, the stator assembly includes a dielectric plate coupled to one of the first slot exit and the second slot exit and configured to suppress surface discharges on windings present at one of the first slot exit and the second slot exit to which the dielectric plate is coupled.