Synchronous Motor Vibration Suppression via Harmonic Current Injection
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Solution Overview
Problem
Polyphase synchronous rotary machines experience large-amplitude rotor vibrations and consequent audible noise due to varying electromagnetic forces acting at frequencies close to resonance frequencies, which existing technologies fail to effectively suppress.
Innovation Solution
A control apparatus that superimposes harmonic-frequency currents with specific angular velocities onto the drive currents in the stator windings of the rotary machine to suppress varying electromagnetic forces, thereby reducing rotor vibrations and noise. This involves calculating suppression-object angular velocities and using current passing circuitry to implement these harmonic frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If sinusoidal-waveform drive currents are supplied to the stator windings, then the rotary machine operates to produce rotation, but varying electromagnetic forces act on the rotor at frequencies close to resonance frequencies, causing large-amplitude rotor vibrations and high audible noise
Solution Approach 1:
The invention applies periodic action by superimposing harmonic-frequency currents (specifically 5th and 7th harmonics) onto the fundamental sinusoidal drive current. These harmonic currents are applied periodically at specific frequencies that correspond to the resonance frequencies of the rotor vibration modes. By doing so, the varying electromagnetic forces are modulated to suppress the resonant vibrations, thereby reducing audible noise while maintaining the rotor rotation speed.
2Object-generated harmful factors
If harmonic-frequency currents are superimposed on drive currents to suppress varying electromagnetic forces, then rotor vibrations and audible noise are reduced, but the current waveform complexity increases
Solution Approach 1:
The invention changes the parameter of current waveform by superimposing specific harmonic-frequency currents (5th and 7th harmonics) onto the fundamental sinusoidal drive current. This parameter change transforms the simple sinusoidal current into a composite waveform containing multiple frequency components. The harmonic currents are carefully selected and adjusted in amplitude and phase to counteract the varying electromagnetic forces that cause rotor vibrations, thereby reducing audible noise while managing the increased waveform complexity through targeted harmonic injection.
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 suppresses rotor vibrations and associated audible noise by aligning the harmonic frequencies with the resonance frequencies of the rotor, reducing noise levels by up to 13 dBA as demonstrated in the embodiments.
Implementation Method 1
when currents are passed through the windings of the stator of a synchronous rotary machine for driving the rotor, varying (i.e., rotating) electromagnetic forces are applied to the rotor
Implementation Method 2
currents are induced in the stator windings whereby the aforementioned varying (i.e., rotating) electromagnetic forces are applied to the rotor
Implementation Method 3
When such a varying electromagnetic force has a frequency that is close to a resonance frequency of a vibration mode of the rotor, large-amplitude vibration of the rotor may occur
Data Source
AI summary
In a synchronous rotary machine such as a synchronous motor, respective values of the number of pole pairs of the rotor and the number of stator slots are predetermined such as to enable drive currents to be passed through the stator windings which suppress specific varying electromagnetic forces that act on the rotor and produce vibration. The drive current of each phase of the motor consists of a fundamental-frequency sinusoidal waveform current having specific harmonic-frequency currents superimposed thereon, the harmonic-frequency currents having angular velocities which are appropriate, with respect to the angular variation velocities of the specific varying electromagnetic forces, for suppressing these forces.