Electric Motor Power Estimation Using Magnetic Harmonic Ratios
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Solution Overview
Problem
Existing methods for estimating the power output of electric motors, particularly 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 it into frequency data, determining harmonic frequencies and their amplitude ratios to estimate power output without the need for torque, voltage, or current sensors, leveraging the correlation between harmonic frequency ratios and motor load.
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 replaces the mechanical slip-based measurement system with a magnetic field-based measurement system. Instead of using torque meters, voltage sensors, or current sensors, the invention uses magnetic field sensors to detect the magnetic field generated by the motor, transforms it to frequency data, and determines power output from harmonic frequency ratios. This substitution maintains ease of installation while significantly improving measurement precision across all load ranges.
2Measurement precision
If voltage, current, or torque sensors are used, then power output measurement precision is improved, but device complexity and installation difficulty increase
Solution Approach 1:
The patent extracts only the essential measurement function needed for power output estimation, eliminating the need for complex sensor systems. By using magnetic field sensors that can be installed externally without integrating into the industrial process, the invention achieves accurate power measurement while dramatically reducing device complexity and installation difficulty.
3Ease of operation
If slip-based estimation is used, then ease of operation is improved, but reliability deteriorates for motors operating below 50% nominal load
Solution Approach 1:
The patent changes the measurement parameter from slip (which has non-linear relationship with power at low loads) to magnetic field harmonic frequency ratios. By transforming the magnetic field signal to frequency data and using the ratio of harmonic frequencies to fundamental frequency, the invention maintains a reliable and consistent relationship with power output across all load ranges, including low loads where slip-based methods fail.
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 with small speed, without the need for classic sensors, offering ease of installation and cost-effectiveness, and works across a range of loads, including low loads where traditional methods fail.
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 it into frequency data, determining harmonic frequencies and their amplitude ratios
Data Source
AI summary
A system and method for estimating a power output of an electric motor with at least one magnetic field sensor includes providing magnetic field signal data, providing magnetic field frequency data based on the magnetic field signal data, determining a fundamental harmonic frequency of the supply frequency and at least one further frequency, 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, and estimating the power output of the electric motor based on the reference ratio data and the determined ratio.