Asynchronous Machine Control Device Resonance Noise
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Solution Overview
Problem
Asynchronous machines emit significant airborne noise due to excitation of natural and resonance frequencies, particularly at certain speed ranges, which is undesirable and affects the machine's design and power density.
Innovation Solution
A control method and device that calculate and adjust the slip frequency of an asynchronous machine by varying the ratio between longitudinal and quadrature current values, avoiding resonance frequencies by comparing calculated excitation frequencies with predetermined resonance values, thus minimizing noise emission without compromising efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the asynchronous machine operates at certain speed ranges, then the power output is maintained, but natural frequencies are excited causing resonances and increased airborne noise
Solution Approach 1:
The invention changes the operating parameters by adjusting the slip frequency to shift the excitation frequency away from resonance frequencies. The control device calculates the excitation frequency based on rotor speed and slip frequency, then modifies the slip frequency to avoid resonant conditions while maintaining the required torque output.
Solution Approach 2:
The invention implements dynamic control of the operating point trajectory in the torque-slip frequency plane. The control device continuously adjusts the slip frequency based on the current rotor speed and torque requirements, creating a dynamic operating trajectory that avoids resonance frequencies across the entire speed range.
2Object-generated harmful factors
If the operating point trajectory is corrected to avoid resonance frequencies, then noise emission is reduced, but the target torque must be maintained constant requiring adjustment of current ratio
Solution Approach 1:
The control device uses feedback by continuously calculating the excitation frequency from measured rotor speed and slip frequency, comparing it with known resonance frequencies, and adjusting the slip frequency accordingly to maintain operation away from resonant conditions while preserving torque output.
3Object-generated harmful factors
If the ratio between longitudinal and quadrature current values is adjusted to change slip frequency, then excitation frequency is shifted away from resonance, but the operating point deviates from optimal efficiency trajectory
Solution Approach 1:
The invention changes the slip frequency parameter to shift excitation frequencies away from resonance. By adjusting the ratio of longitudinal to quadrature current components, the slip frequency is modified to avoid resonant conditions while the control system compensates to maintain the required torque output.
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 approach effectively reduces airborne noise by preventing the excitation of resonance frequencies, relaxing acoustic requirements across all speed ranges with minimal impact on efficiency, achieving noise reduction of up to 5 dB at critical frequencies.
Implementation Method 1
an asynchronous machine, with a control module which is designed to calculate an operating point trajectory for the asynchronous machine by calculating 2 tuples from longitudinal current values and transverse current values in a synchronously rotating coordinate system of the asynchronous machine
Implementation Method 2
comparing the calculated excitation frequency of the asynchronous machine with at least one predetermined resonant frequency value of the asynchronous machine
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a method for operating an asynchronous machine comprising the steps: determining an operating point trajectory for the asynchronous machine for a plurality of desired torques of the asynchronous machine by calculating 2-tuples from longitudinal current values and cross current values in a synchronously rotating coordinate system of the asynchronous machine; calculating a slip frequency of the asynchronous machine for each of the 2-tuples calculated from longitudinal current values and cross current values; determining a current rotor speed of the asynchronous machine; calculating an excitation frequency of the asynchronous machine by summation of the calculated slip frequency and the current rotor speed weighted with the number of pole pairs of the asynchronous machine; and comparing the calculated excitation frequency of the asynchronous machine with at least one predetermined resonance frequency value of the asynchronous machine. The determined operating point trajectory is thereby corrected by changing the ratio between longitudinal current value and cross current value at a constant desired torque for each of the 2-tuples for which the calculated excitation frequency corresponds to the at least one resonance frequency value.