SRM Current Waveform Control for Radial Force Harmonics Reduction
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Solution Overview
Problem
Switched reluctance motors (SRMs) face challenges with high acoustic noise and vibration due to radial force harmonics, which existing methods have not fully addressed, particularly at specific harmonics like the 2nd, 4th, 5th, 7th, and 8th harmonics, necessitating a more effective solution for noise reduction without additional components.
Innovation Solution
An acoustic noise reduction system that generates an optimum current waveform to reduce the amplitude of specific radial force harmonics at stator teeth, utilizing a processor to calculate and regulate currents, thereby minimizing vibration and acoustic noise. This system includes a Fourier series equation for reference current generation, maximum current rate calculation, torque determination, and radial force harmonic analysis to select the optimal current waveform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional current waveforms are used in SRMs, then the motor can operate at high temperatures and speeds with high reliability, but high acoustic noise and vibration occur due to radial force harmonics
Solution Approach 1:
The patent modifies the current waveform parameters (amplitude, duration, timing) to reduce radial force harmonics. By changing the excitation parameters rather than the motor structure, the noise and vibration are reduced while maintaining operational reliability at high temperatures and speeds.
Solution Approach 2:
The patent implements dynamic current adjustment during motor operation, modifying the current waveform in real-time based on rotor position and operating conditions. This dynamic control reduces radial force harmonics across different operating points, addressing noise and vibration while preserving reliability.
2Object-affected harmful factors
If existing noise reduction methods (spacers, windowed structure, skewing) are implemented, then acoustic noise is reduced, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent replaces mechanical noise reduction methods (spacers, windowed structures, skewing) with an electrical control solution. By substituting the mechanical approach with current waveform optimization, the patent reduces acoustic noise without increasing structural complexity or manufacturing cost.
Solution Approach 2:
Instead of changing the physical structure of the motor, the patent changes the electrical parameters (current waveform characteristics) to achieve noise reduction. This parameter-based approach avoids the complexity and cost associated with structural modifications.
3Object-affected harmful factors
If active vibration cancellation methods are used, then noise at natural frequencies is reduced, but only one frequency component can be eliminated while multiple frequency components exist
Solution Approach 1:
The patent segments the radial force harmonics into multiple frequency components and addresses each segment separately through targeted current waveform optimization. By dividing the noise reduction task into multiple frequency-specific adjustments, the patent can eliminate multiple frequency components simultaneously.
Solution Approach 2:
The patent employs periodic current waveform adjustments synchronized with the motor's rotational frequency and its harmonics. This periodic control strategy enables the system to address multiple frequency components by applying corrective actions at appropriate intervals throughout each rotation cycle.
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
Significantly reduces acoustic noise at specific harmonics by up to 21.17 dB, improving efficiency and reducing torque ripple, while operating at high temperatures and speeds without additional components, and enhancing system performance.
Implementation Method 1
A Fourier series equation is used to generate a plurality of reference currents
Implementation Method 2
An acoustic noise reduction system that generates an optimum current waveform to reduce the amplitude of specific radial force harmonics at stator teeth, utilizing a processor to calculate and regulate currents
Data Source
AI summary
An SR drive with an acoustic noise reduction system for reducing vibration and acoustic noise in a switched reluctance motor (SRM). The vibration and acoustic noise at specific harmonics of current excitation in SRM are in a proportional relationship with the radial force harmonics acting at SRM stator teeth. The acoustic noise reduction system includes a processor on which is installed an acoustic noise reduction application designed to derive an optimum current waveform for generating an average torque satisfying an optimum torque condition and creating radial force with minimum amplitude at the desired order of harmonics of current excitation. A reduction in the amplitude of the specific radial force harmonics utilizing the optimum current waveform minimizes the vibration and acoustic noise in the SRM. The acoustic noise reduction system applies turn-on and turn-off angles at the optimum current waveform to improve the system efficiency.