Electrical Machine Reliability Estimation from Current-Based Temperature
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Solution Overview
Problem
Traditional methods for determining the reliability of electrical machines, such as MTBF, are computationally expensive, require additional sensors, and are not generalized for various types of failures, making them impractical for aerospace applications with space and weight constraints.
Innovation Solution
Estimate the operating temperature of electrical machines using existing current sensors and known electrical properties, then use an Arrhenius model to determine reliability parameters like MTBF, considering both thermal and electrical stress through a power-based model.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional methods use thermocouples to determine temperature for MTBF calculation, then temperature measurement is achieved, but additional sensors are required and placement location causes over- or underprediction
Solution Approach 1:
The electrical machine's existing current sensors serve dual purposes: monitoring current for operation control and providing data for temperature estimation through power loss calculation. The system uses its own operational parameters (current, voltage, impedance) to self-determine temperature without external thermocouples, eliminating additional sensor installation while maintaining measurement capability
Solution Approach 2:
The patent replaces the mechanical/physical thermocouple measurement system with an electrical calculation system. Instead of physically measuring temperature with thermocouples, the system calculates temperature by measuring electrical parameters (current, voltage, impedance) and computing power losses, substituting direct thermal measurement with indirect electrical inference
2Reliability
If traditional methods use large databases of historical or accelerated aging data, then reliability parameters can be estimated, but calculations are computationally expensive and time consuming
Solution Approach 1:
The patent pre-establishes the relationship between power loss and temperature, and between temperature and reliability parameters during the design phase or through simplified calibration. This preliminary characterization allows real-time reliability assessment using only current operational data without requiring access to large historical databases or performing computationally intensive calculations during operation
Solution Approach 2:
The system transitions from using static historical database values to using dynamic real-time operational parameters (current, voltage, power loss). By continuously monitoring and updating these parameters during machine operation, the system achieves current-relevant reliability assessment without the computational burden of processing large historical datasets
3Measurement precision
If thermocouples are placed in particularly hot or cool regions, then temperature measurement is obtained, but MTBF is over- or underpredicted
Solution Approach 1:
The power loss-based temperature estimation method provides a universal temperature indicator that represents the overall thermal state of the electrical machine regardless of specific location. Unlike thermocouples that measure only local temperature at their placement point, this method captures the cumulative effect of losses throughout the machine, providing a location-independent temperature metric that better correlates with overall reliability
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
Provides accurate and efficient determination of reliability parameters without additional sensors, accounting for thermal and electrical stresses, enhancing maintenance planning and system health monitoring.
Implementation Method 1
resistive loss, such as a winding loss
Implementation Method 2
magnetic loss, such as a core loss
Implementation Method 3
rate of dissipated heat, being a rate of heat dissipated by at least a part of the electrical machine
Data Source
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AI summary
A computer-implemented method of determining a value of a reliability parameter of an electrical machine, the method comprising: estimating an operating temperature of at least a part of the electrical machine based on a measure of a current drawn or supplied by the electrical machine; and determining the value of the reliability parameter based on the estimated operating temperature.