Electric Machine State Monitoring via Phase-Based Slip Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional motor current signature analysis (MCSA) for electric machines is imprecise in detecting dynamic slip and faults due to small current amplitudes and noise interference, especially in the frequency ranges of principal slot harmonics, which are affected by grid voltage components and other power-consuming loads.
Innovation Solution
A method that determines a frequency position or line within a defined range by maximizing current amplitude and ensuring a specific phase relationship between current and voltage vectors falls within a predefined interval, allowing for robust and accurate slip and fault detection, even in noisy conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional MCSA is used to detect slip and faults in electric machines, then the method can identify frequency components, but the detection precision deteriorates due to small current amplitudes and noise interference in the frequency ranges of principal slot harmonics
Solution Approach 1:
The patent extracts and utilizes the phase relationship information between current and voltage vectors as a separate diagnostic parameter. By calculating the phase angle at detected frequency positions and comparing it against expected phase relationships for different machine states, the method isolates useful diagnostic information from the noisy current spectrum, enabling accurate fault detection even when current amplitudes are small
Solution Approach 2:
The patent introduces voltage measurement as an intermediary parameter to resolve the ambiguity in current spectrum analysis. The voltage signal serves as a reference that, when combined with current measurements, provides phase relationship information that acts as a mediator to distinguish true fault signatures from noise and interference in the frequency domain
2Reliability
If the current amplitude is maximized to improve detection, then the signal strength increases, but noise and interferences from grid voltage components and other loads also increase
Solution Approach 1:
The patent changes the parameter used for detection from relying solely on current amplitude to utilizing phase relationship between current and voltage vectors. This parameter transformation allows the system to maintain detection reliability without being adversely affected by increases in noise and interference that accompany higher current amplitudes
Solution Approach 2:
The patent exploits the asymmetric phase relationship characteristics between current and voltage under different machine operating conditions. Healthy machines, faulty machines, and different fault types exhibit distinct phase angle patterns that differ from the symmetric noise distribution, enabling reliable detection even in the presence of interference
Data Source
AI summary
A method for monitoring the state of an electric machine includes determining within a defined frequency range, for example in a spectrogram of a current amplitude, a frequency position where a current amplitude has a maximum at the frequency position and where a phase relationship between a current vector and a voltage vector or between two current vectors is located in a predefined interval. The determined frequency position is characteristic of the state of the electric machine.