Inverter Spread-Spectrum Switching for Electromagnetic Noise Control
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Solution Overview
Problem
Existing inverters for electric machines generate unwanted electromagnetic noise due to a continuous fundamental switching frequency, which requires output filters that increase cost, weight, and thermal dissipation, and can cause unintended attenuation or phase distortion, affecting control accuracy and rotor position sensing.
Innovation Solution
An inverter with a dynamic spread-spectrum control module that changes the fundamental switching frequency based on a threshold, using a controller and driver circuit to step the frequency by a fixed amount, reducing noise within a target frequency band by mimicking white or Gaussian noise, thereby eliminating the need for output filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a continuous fundamental switching frequency is used, then the inverter can operate efficiently, but unwanted electromagnetic noise is generated within a confined frequency range
Solution Approach 1:
The patent applies dynamics by making the switching frequency variable rather than fixed. The controller dynamically adjusts the fundamental switching frequency around a target frequency according to a spread-spectrum control process, changing the frequency over time to distribute electromagnetic noise across a broader spectrum while maintaining operational efficiency
Solution Approach 2:
The patent changes the frequency parameter of the switching signals. By varying the fundamental switching frequency around a target frequency using spread-spectrum control, the system transforms concentrated electromagnetic noise into distributed noise across a wider frequency range, reducing peak noise levels while maintaining efficiency
2Object-generated harmful factors
If an output filter is used to reduce electromagnetic noise, then noise is attenuated, but cost, weight, and thermal dissipation increase
Solution Approach 1:
The patent converts the harmful concentrated electromagnetic noise into a beneficial distributed noise spectrum. By using spread-spectrum control to vary the switching frequency, the system transforms peak noise concentrations into lower-level distributed noise, eliminating the need for heavy output filters while actually reducing overall electromagnetic interference
Solution Approach 2:
The patent extracts the noise reduction function from the physical output filter hardware and implements it through control software. Instead of using a heavy filter component to remove noise, the system uses spread-spectrum frequency modulation to prevent noise concentration in the first place, removing the need for bulky filtering hardware
3Object-generated harmful factors
If an output filter is used to reduce electromagnetic noise, then noise is attenuated, but unintended attenuation or phase distortion of the alternating current signal occurs
Solution Approach 1:
The patent converts the harmful effect of electromagnetic noise into a beneficial control mechanism. By using spread-spectrum frequency variation, the system prevents noise concentration without introducing the signal attenuation and phase distortion that physical filters cause, thereby maintaining accurate control and rotor position sensing
Solution Approach 2:
The patent introduces frequency modulation as an intermediary mechanism between the switching circuit and the output. Instead of directly filtering the output signal (which causes distortion), the system uses frequency variation as an intermediate step to distribute noise energy, preserving signal integrity while reducing electromagnetic interference
Data Source
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AI summary
An electronic data processor comprises a data storage device in communication with the electronic data processor. A control module stored in the data storage device, the control module comprising software instructions for execution by the electronic data processor to change dynamically the fundamental switching frequency of the control signals to reduce electromagnetic noise within a target frequency band if the fundamental switching frequency is equal to or greater than a threshold fundamental switching frequency.