Permanent Magnet Rotor Demagnetization Detection via Open-Circuit Voltage
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Solution Overview
Problem
Existing methods for detecting rotor demagnetization in permanent magnet synchronous electrical machines (PMSMs) are complex and require extensive experimental or historical data, and they do not effectively address the issue of rotor demagnetization caused by adverse conditions like high temperatures, leading to performance degradation and potential further demagnetization.
Innovation Solution
A method involving a control and health monitoring system that supplies power to polyphase winding sets, measures voltages across open circuit winding sets, and calculates magnetic flux linkage indicators to determine rotor demagnetization by comparing a ratio of these indicators to predefined thresholds, utilizing electrical machines with multiple isolated polyphase winding sets and DC:AC power converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex time- or frequency-domain analysis with threshold values derived from large amounts of experimental or historical data is used to detect rotor demagnetization, then detection accuracy may be improved, but system complexity and data requirements increase significantly
Solution Approach 1:
The patent extracts the essential detection function by using a single voltage measurement at a specific operating point (zero current condition) rather than complex continuous analysis. This isolates the critical measurement needed for demagnetization detection, eliminating the need for extensive data processing while maintaining detection accuracy.
Solution Approach 2:
The patent changes the operating parameters to a specific condition (zero current, open circuit voltage measurement) where the detection is most effective. By operating at this specific parameter point, the system achieves high detection sensitivity without requiring complex analysis algorithms or historical data.
2Reliability
If extensive experimental or historical operating data is collected to derive threshold values for demagnetization detection, then detection reliability improves, but data collection time and system downtime increase
Solution Approach 1:
The patent performs preliminary characterization during manufacturing to establish baseline flux linkage values, storing these in memory for later comparison. This preliminary action eliminates the need for extensive field data collection, as the thresholds are pre-determined under controlled conditions and can be immediately applied during operation.
3Difficulty of detecting and measuring
If continuous monitoring and complex analysis are performed to detect rotor demagnetization, then detection capability improves, but computational resources and processing complexity increase
Solution Approach 1:
The system uses its own existing voltage and current measurements, which are already taken for normal operation, to perform demagnetization detection. The control processor utilizes measurements that would otherwise be discarded or used for basic control, eliminating the need for additional sensors or dedicated detection hardware.
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
Enables efficient detection of rotor demagnetization without extensive testing or historical data, reduces system downtime, and maintains high reliability by using simple threshold comparisons and low-complexity processing, applicable to various PMSM types.
Implementation Method 1
measuring a first voltage across the first polyphase winding set of the first electrical machine... determining first and second magnetic flux linkage indicators based on the first and second voltages
Data Source
Figure 1~2
Figure 3A~3B
Figure 4
AI summary
Electrical power systems and methods of operating electrical power systems are provided. In one aspect, an electrical power system comprises first and second electrical machines, each comprising a permanent magnet rotor and a stator comprising a plurality of electrically isolated polyphase winding sets; and a control and health monitoring system configured to detect rotor demagnetization of the first and/or second electrical machine by: supplying electrical power to each polyphase winding set of the plurality of polyphase windings sets of the first electrical machine; stopping the supply of electrical power to a first polyphase winding set of the first electrical machine; measuring a first voltage across the first polyphase winding set of the first electrical machine; supplying electrical power to each polyphase winding set of the plurality of polyphase windings sets of the second electrical machine; stopping the supply of electrical power to a first polyphase winding set of the second electrical machine; measuring a second voltage across the first polyphase winding set of the second electrical machine; determining first and second magnetic flux linkage indicators based on the first and second voltages; and determining whether the permanent magnet rotor of the first and/or second electrical machine is demagnetized based on the whether a ratio of the first and second magnetic flux linkage indicators passes a threshold.