Electric Motor Thermal Model Updating With Fewer Temperature Sensors
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Solution Overview
Problem
Existing thermal models for electric motors require numerous sensors and continuous parameter updates, which are costly and inefficient, necessitating a more standardized and resource-minimal approach to maintain accuracy.
Innovation Solution
A method involving injecting current into stator windings, obtaining temperature measurements over time, and updating thermal model parameters based on these measurements to adapt the model to the motor's thermal behavior, using a system identification process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If many sensors are put inside and outside the machine to implement advanced thermal models, then the accuracy of thermal behavior modeling is improved, but the cost and hardware resources increase significantly
Solution Approach 1:
The patent uses temperature symmetry relationships to create virtual temperature measurements from limited physical sensors. By exploiting the symmetric thermal behavior of motor components, the system copies temperature data from measured locations to unmeasured symmetric locations, reducing the number of physical sensors needed while maintaining modeling accuracy.
Solution Approach 2:
The patent makes existing temperature sensors serve multiple functions by utilizing them for both direct temperature measurement and for inferring temperatures at other locations through symmetry relationships. This multi-functional use of sensors reduces the total number of sensors required in the system.
2Reliability
If model parameters are updated continuously under varying conditions, then the thermal model remains accurate over time, but the complexity and resource requirements increase
Solution Approach 1:
The patent updates thermal model parameters by performing system identification using temperature symmetry relationships under varying operating conditions. The method changes parameters (thermal resistances and capacitances) based on measured temperature differences between symmetric locations, allowing the model to adapt to aging and condition changes without requiring continuous complex recalibration.
Solution Approach 2:
The patent implements a feedback mechanism where temperature measurements from symmetric locations are continuously monitored, and parameter updates are triggered when temperature differences exceed thresholds. This feedback-based approach ensures model accuracy is maintained while avoiding unnecessary updates under stable conditions.
3Measurement precision
If temperature measurements are taken during cooldown phase, then both thermal resistances and capacitances can be updated, but the timing and control of measurement becomes more complex
Solution Approach 1:
The patent performs temperature measurements during the cooldown phase after the motor has been operated under load. This preliminary action of heating the motor before measurement ensures that sufficient temperature gradients exist to accurately identify both thermal resistances and capacitances, while the cooldown phase provides a controlled environment for measurements.
Solution Approach 2:
The patent utilizes the periodic nature of motor operation cycles (load followed by cooldown) to perform parameter identification. By scheduling measurements during the natural cooldown phases that occur periodically in motor operation, the system captures necessary thermal data without requiring separate dedicated measurement periods.
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 thermal model is accurately updated to reflect the motor's changing characteristics, reducing sensor requirements and maintaining high accuracy with less hardware, enabling efficient parameter adaptation.
Implementation Method 1
a) injecting a current into the stator windings to heat the stator windings
Implementation Method 2
b) obtaining temperature measurements over time from each of a plurality of temperature sensors distributed in the electric motor while step a) is being performed and the stator windings are heating up, or after step a) has been terminated or the current has been decreased, and the electric motor is cooling down
Data Source
AI summary
A method of updating a thermal model describing the thermal behaviour of an electric motor having a stator provided with stator windings, the method including: a) injecting a current into the stator windings to heat the stator windings, b) obtaining temperature measurements over time from each of a plurality of temperature sensors distributed in the electric motor while step a) is being performed and the stator windings are heating up, or after step a) has been terminated or the current has been decreased, and the electric motor is cooling down, and c) updating parameter values of the thermal model based on the temperature measurements.