Comb Elements for Rotary Machine Noise Reduction
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Solution Overview
Problem
Tonal noises in air-cooled and open-circuit ventilated rotary dynamoelectric machines are caused by aeroacoustic interactions between the stator and rotor, particularly due to the radial distance between the squirrel cage ring and the rotor laminated core, leading to pressure fluctuations and sound generation.
Innovation Solution
A stator with a winding system in grooves between magnetically conductive teeth, featuring comb-type elements on the end faces that eliminate radial intermediate spaces, ensuring the air flow is directed tangentially or axially, reducing interactions and noise emissions. The comb-type elements are made from insulating material, attached using dual-sided adhesive tape, and cured to form a robust cylindrical surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a distance is maintained between the squirrel cage ring and the rotor laminated core, then assembly ease and structural integrity are improved, but tonal noise emissions increase due to aeroacoustic interactions
Solution Approach 1:
The patent introduces an intermediary substance (resin or adhesive) in the gap between the rotor bars and the squirrel cage ring. This intermediary fills the radial intermediate space and prevents direct aeroacoustic interaction between the rotating rotor bars and the stator winding coils, thereby reducing tonal noise while maintaining the beneficial distance for assembly and structural integrity
Solution Approach 2:
The patent changes the physical state and properties of the gap material by applying resin or adhesive that cures to form a solid filling. This transforms the gap from an empty space that allows air flow and noise generation into a filled space that eliminates the harmful aeroacoustic interactions while preserving the structural distance
2Object-generated harmful factors
If radial intermediate spaces are eliminated between winding coils and rotor rods, then tonal noise is reduced, but cooling efficiency may worsen due to restricted air flow
Solution Approach 1:
The patent applies the intermediary resin or adhesive selectively only in the radial intermediate spaces where noise is generated, while leaving other pathways for air flow intact. This localized treatment eliminates noise at the specific interaction points between rotor bars and stator coils without blocking the overall cooling air flow through the motor structure
Solution Approach 2:
The resin or adhesive acts as a mediator that blocks the specific air flow path responsible for noise generation between the rotor bars and stator winding coils, while allowing cooling air to continue flowing through alternative paths such as axial ventilation channels and inter-laminar spaces
3Object-generated harmful factors
If comb-type elements are attached to end faces of the stator, then tonal noise is reduced by eliminating intermediate spaces, but device complexity increases
Solution Approach 1:
The comb-type elements are segmented into multiple identical units that can be attached to the end faces of the stator in a modular fashion. Each segment corresponds to a specific phase or pole, and the repetitive pattern simplifies the attachment process and reduces the complexity of implementing the noise reduction solution across the entire stator structure
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 reduces or prevents tonal noise emissions by eliminating radial gaps between the winding coils and rotor rods, improving cooling efficiency and preventing flashovers, while maintaining structural integrity and assembly ease.
Implementation Method 1
impregnating and curing the magnetically conductive body with winding system and elastic elements, wherein in the process the elastic property of the elements gets lost and a robust, essentially cylindrical surface is thus produced
Implementation Method 2
aeroacoustic interactions between the winding coils of the winding system emerging on the end face of the stator and the rods of the rotor. The rods of the rotor rotating rapidly past the vertical winding coils of the stator result in pressure fluctuations, which induce tonal noises
Data Source
AI summary
A dynamoelectric rotary machine includes a stator, which has a winding system arranged in grooves disposed between teeth of a magnetically conductive body and a winding head on the end faces of the stator in each case. A rotor with a cage ring is arranged rotatably about an axis and during operation of the dynamoelectric rotary machine is in electromagnetic interaction in a motor-driven or generator-driven manner with the winding system of the stator arranged in the grooves by way of an air gap. Comb-type elements are disposed on the end faces of the stator. The comb-type elements assume an extensive intermediate space between the winding system projecting from the end faces of the stator, so that tonal noises which are produced during operation of such an electric machine are at least reduced.