PMSM Inter-Turn Fault Estimation Using Standstill DC Resistance
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Solution Overview
Problem
Existing methods for detecting and estimating the severity of inter-turn short circuit faults in permanent magnet synchronous motors (PMSM) are complex, prone to errors due to machine model dependencies, inverter non-linearity, and require additional hardware, making them unreliable for continuous monitoring and fault severity assessment.
Innovation Solution
A method that estimates the fault severity index and number of shorted turns by calculating the resistance of the remaining healthy coils using DC voltage excitation at standstill conditions, eliminating the need for complex machine modeling and additional hardware, and is immune to inverter non-linearity effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If motor current signature analysis (MCSA) is used to detect inter turn short circuit faults, then fault detection capability is improved, but measurement precision deteriorates due to heavy dependence on machine model operating point and winding configuration
Solution Approach 1:
The patent extracts only the resistance component from the impedance measurement by using DC excitation at standstill conditions. This eliminates the influence of inductance, back EMF, and other operating-point-dependent parameters, leaving only the resistive component that directly reflects the health of the winding insulation.
Solution Approach 2:
The patent replaces the complex AC-based MCSA method with a simple DC resistance measurement approach. By substituting AC excitation with DC excitation at standstill, the system eliminates the need for complex machine models, FFT analysis, and harmonic detection, achieving more reliable fault detection through a fundamentally simpler measurement principle.
2Difficulty of detecting and measuring
If Fourier-transform-based methods are used for fault detection, then fault detection capability is improved, but device complexity increases due to requirement of fast Fourier transform and harmonic analysis
Solution Approach 1:
The patent extracts only the resistive component of impedance by performing DC resistance measurement at standstill. This extraction eliminates the need for Fourier transforms, harmonic analysis, and complex signal processing, reducing device complexity while maintaining fault detection capability.
Solution Approach 2:
The patent uses a simple, low-cost DC resistance measurement approach instead of expensive and complex FFT-based analysis systems. The method uses basic ohmmeter functionality that is already present in most motor control systems, eliminating the need for additional complex hardware or software processing capabilities.
3Difficulty of detecting and measuring
If high frequency signal injection method is used to diagnose inter turn short circuit faults, then fault detection capability is improved, but use of energy increases due to injection of high frequency voltages or currents
Solution Approach 1:
The patent extracts fault information using only DC resistance measurement at standstill, completely eliminating the need for high frequency signal injection. This extraction approach uses minimal energy while still providing accurate fault detection by measuring only the resistive component of the winding impedance.
Solution Approach 2:
The patent uses a simplified copy of the impedance measurement principle - instead of measuring full AC impedance with high frequency injection, it measures only the DC resistance component. This copied approach uses a fraction of the energy while providing equivalent or superior fault detection capability.
4Difficulty of detecting and measuring
If parameter identification method is used to monitor stator winding impedance changes, then fault detection capability is improved, but device complexity increases due to saturation effects and complex modeling requirements
Solution Approach 1:
The patent extracts only the resistance component from impedance measurement by using DC excitation. This extraction eliminates the need to model saturation effects, inductance variations, and other complex phenomena, simplifying the device while maintaining fault detection capability.
Solution Approach 2:
The patent replaces complex parameter identification and modeling methods with simple DC resistance measurement. By substituting AC-based impedance modeling with DC resistance measurement, the system eliminates the need for saturation modeling, magnetic circuit analysis, and complex parameter identification algorithms.
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 provides accurate and robust estimation of fault severity and number of shorted turns, enhancing the reliability of fault detection and enabling safe operating conditions to prevent motor damage, without requiring additional sensors or complex calculations.
Implementation Method 1
calculating the resistance of the remaining healthy coils using DC voltage excitation at standstill conditions
Data Source
AI summary
A system and method estimate the fault severity index and consequently the number of shorted turns in permanent magnet motors (PMSM) with inter turn short circuit fault (ITSC). In this method, the machine is excited with DC current at stand still conditions to obtain the winding resistance seen by the d-axis of the machine. The estimated d-axis resistance contains useful information pertaining to the fault severity index, and is used to extract the fault severity index and the number of shorted turns in the faulty motor. The method enables the estimation of fault severity index without complex modeling with different machine prototypes, or FEA models to analyze the relationship between machine currents and short circuit current. To enhance the accuracy of the estimation method, this disclosure addresses issues associated with inverter non-linearity effects such as distortion voltage due to dead time effects and voltage drops across the switching devices.