Variable Speed Drive Harmonic Injection for Single Phase Motors
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Solution Overview
Problem
Single phase motor systems experience unacceptable acoustic noise and torque pulsations when operated at variable speeds, which are not effectively addressed by traditional noise suppression techniques, and they struggle to maintain consistent fluid pressure and speed due to inherent design limitations.
Innovation Solution
A system comprising an inverter and a processing unit that generates a control voltage with a fundamental component and odd-numbered harmonic components to reduce torque pulsations, incorporating a skip frequency selection device to mitigate noise, while maintaining voltage and current crest factors below specific thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If variable speed control is applied to single phase motors, then the variability of fluid characteristics is reduced, but acoustic noise and torque pulsations are magnified
Solution Approach 1:
The patent changes the voltage waveform parameters by injecting odd harmonics (3rd, 5th, 7th, etc.) into the control voltage signal. This modifies the voltage characteristics to reduce torque pulsations and acoustic noise while maintaining variable speed operation benefits. The harmonic injection alters the electrical parameters to achieve smoother motor operation.
2Stability of the object's composition
If variable speed control is applied to single phase motors, then the variability of fluid characteristics is reduced, but torque pulsations are magnified
Solution Approach 1:
The patent changes the voltage waveform parameters by injecting odd harmonics (3rd, 5th, 7th, etc.) into the control voltage signal. This modifies the voltage characteristics to reduce torque pulsations and acoustic noise while maintaining variable speed operation benefits. The harmonic injection alters the electrical parameters to achieve smoother motor operation.
3Object-affected harmful factors
If traditional noise suppression techniques are used, then acoustic noise is reduced, but torque pulsations and fluid pressure consistency are not effectively addressed
Solution Approach 1:
The patent changes the voltage waveform parameters by injecting odd harmonics (3rd, 5th, 7th, etc.) into the control voltage signal. This modifies the voltage characteristics to reduce torque pulsations and acoustic noise while maintaining variable speed operation benefits. The harmonic injection alters the electrical parameters to achieve smoother motor operation.
Solution Approach 2:
The system monitors fluid pressure and motor operation parameters, using this feedback to adjust the harmonic injection strategy. The controller dynamically modifies the control voltage to maintain fluid pressure consistency while suppressing torque pulsations and noise through adaptive parameter adjustment.
4Object-generated harmful factors
If harmonic components are added to control voltage, then torque pulsations are reduced, but total harmonic distortion increases
Solution Approach 1:
The patent carefully controls the parameters of injected harmonics (amplitude, phase, frequency order) to reduce torque pulsations. By selecting specific odd harmonics and optimizing their magnitudes, the system achieves torque smoothing while keeping total harmonic distortion within acceptable limits (below 50% as specified).
Solution Approach 2:
The patent applies harmonic injection selectively at specific frequency components (odd harmonics: 3rd, 5th, 7th, etc.) rather than uniformly across all frequencies. This localized approach targets the specific harmonic content that causes torque pulsations while minimizing overall distortion and maintaining power quality.
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 significantly reduces torque and speed ripples, acoustic noise, and fluid pressure ripples by up to 10%, while maintaining total harmonic distortion below 50% and crest factors within acceptable limits, enhancing the operational stability and efficiency of single phase motor systems.
Implementation Method 1
an inverter adapted to provide a driving voltage to a single phase motor and a processing unit generating a control voltage Vhew(t) to cause the inverter to provide the driving voltage
Data Source
AI summary
This disclosure relates to a variable speed drive for driving a single phase motor. The variable speed drive generates enhanced motor voltages including harmonic components configured to reduce torque pulsations.