Electric Motor Power Estimation from Magnetic Field Harmonics
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Solution Overview
Problem
Existing methods for estimating the power output of electric motors, especially asynchronous motors, face inaccuracies when operating at low loads due to non-linear relationships between slip and power, and require expensive sensors like voltage, current, or torque meters, which are difficult to install.
Innovation Solution
A computer-implemented method using magnetic field sensors to measure the magnetic field and transform the data into frequency domain, determining harmonic frequencies and their amplitudes to estimate power output without the need for traditional sensors, by calculating ratios between harmonic frequencies and the fundamental frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If slip-based power estimation is used, then power output can be estimated without expensive sensors, but measurement precision deteriorates when motor operates at low loads
Solution Approach 1:
The patent changes the measurement parameter from slip (which is non-linear at low loads) to magnetic field harmonic amplitude ratios. By using the ratio of harmonic amplitudes (e.g., 3rd harmonic to fundamental frequency) in the magnetic field spectrum, the system achieves linear and accurate power estimation across the entire load range including low loads, while still avoiding expensive torque sensors.
2Measurement precision
If voltage and current sensors are used for power measurement, then measurement precision improves, but device complexity and installation difficulty increase
Solution Approach 1:
The patent extracts only the necessary information (magnetic field harmonic content) from the motor system without requiring physical contact with electrical circuits or mechanical components. By using external magnetic field sensors to measure the magnetic spectrum, the system obtains accurate power measurements without integrating voltage or current sensors into the motor's electrical system, thus reducing installation complexity while maintaining precision.
Solution Approach 2:
The patent replaces the traditional electrical measurement approach (voltage and current sensors requiring circuit integration) with a magnetic field-based measurement system. This substitution allows non-contact measurement of power output by analyzing the magnetic field harmonics generated by the motor, eliminating the need for complex electrical sensor installation while preserving measurement accuracy.
3Measurement precision
If torque meters are used for power measurement, then measurement precision improves, but ease of operation and installation difficulty worsen
Solution Approach 1:
The patent introduces magnetic field harmonic analysis as an intermediary measurement method between the motor and the measurement system. Instead of directly measuring torque mechanically (which requires shaft coupling and complex installation), the system uses magnetic field sensors to detect harmonic amplitudes that correlate with power output. This intermediary approach provides accurate power measurement without direct mechanical contact, greatly simplifying installation while maintaining precision.
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 method provides accurate power estimation for electric motors, including those operating at low loads, without the need for expensive sensors, offering a cost-effective and easier installation process while maintaining precision.
Implementation Method 1
a magnetic field sensor, comprising: providing magnetic field signal data from the magnetic field sensor, wherein the magnetic field sensor is arranged and configured to measure a magnetic field of the electric motor
Implementation Method 2
transform the data into frequency domain, determining harmonic frequencies and their amplitudes
Data Source
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AI summary
The present invention is directed to a computer implemented method for estimating a power output of an electric motor with at least one magnetic field sensor, comprising: - providing magnetic field signal data from the magnetic field sensor, wherein the magnetic field sensor is arranged and configured to measure a magnetic field of the electric motor; - providing magnetic field frequency data based on the magnetic field signal data; - determining a fundamental harmonic frequency of the supply frequency of the electric motor; - determining at least one further harmonic frequency of the fundamental harmonic frequency based on the magnetic field frequency data and/or the magnetic field signal data; - determining a ratio between an amplitude of the at least one further harmonic frequency and an amplitude of the fundamental harmonic frequency ; - providing reference ratio data describing a relation of a ratio between an amplitude of the at least one further harmonic frequency and an amplitude of the fundamental harmonic frequency and a power output of the electric motor; - estimating the power output of the electric motor based on the reference ratio data and the determined ratio.