Electric Machine Noise Reduction via Resonance Frequency Shifting
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Solution Overview
Problem
Electric machines used in motor vehicles, such as supercharged electric compressors, generate noise due to vibrations that interfere with the resonance frequency, causing audible sound pollution, which is difficult to reduce with conventional methods.
Innovation Solution
The electric machine is designed with noise-reducing features, including recesses in the stator and mechanical insulation, to shift its resonance frequency range away from the harmonics, specifically between 1500 Hz and 2500 Hz, using axial and radial insulation means like seals and resin covering, to minimize mechanical stress and sound emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If recesses are created in the stator material to reduce radial forces, then deformation gain is achieved and radial forces are reduced by 10%, but noise remains audible to the human ear
Solution Approach 1:
The invention changes the resonance frequency parameter of the stator by modifying its structural parameters (adding recesses and insulation layers), shifting it from the audible harmonic range (above 2500 Hz) to an inaudible range (below 2500 Hz), thereby reducing perceived noise while maintaining radial force reduction
Solution Approach 2:
The invention uses composite structural elements combining different materials (stator material, insulation material, seals) with different mechanical properties to achieve the desired resonance frequency shift. The composite structure provides both mechanical insulation and acoustic damping properties
2Object-affected harmful factors
If the resonance frequency is shifted below 2500 Hz using recesses and insulation, then noise is reduced to inaudible levels, but the structural complexity increases
Solution Approach 1:
The noise reduction solution is segmented into distinct functional components: recesses for mechanical stress reduction, axial seals for insulation, and radial insulation layers. This segmentation allows each component to be optimized independently while working together to achieve the overall noise reduction goal
Solution Approach 2:
Insulation materials and seals are introduced as intermediary elements between the stator and the external environment. These intermediaries provide mechanical insulation, acoustic damping, and resonance frequency control without requiring complete redesign of the 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
This configuration effectively reduces noise pollution by aligning the machine's resonance frequency outside the audible harmonic range, resulting in a significant noise reduction of 8 to 17 dB across various engine speeds, making the noise no longer perceivable to the human ear.
Implementation Method 1
noise-reducing means configured so as to achieve a resonance frequency of the electric machine lying within a resonance frequency range that does not match the frequency range of the harmonics of the electric machine
Implementation Method 2
the vibrations of the motor can interfere with the resonance frequency of the machine and cause additional vibrations and thus high-frequency micro-displacements within the audible range of the human ear
Data Source
AI summary
The invention relates to an electric machine (1) comprising noise-reducing means (24) designed so as to obtain a resonance frequency of the electric machine within a resonance frequency range that does not match the range of frequency of the harmonics of the electric machine, more precisely between 1500 Hz and 2500 Hz.