Electric Motor Connection Fault Detection via Frequency Comparison
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Solution Overview
Problem
Existing methods fail to promptly detect connection faults in electric motors, such as open-circuit and short-circuit faults, which can lead to unsafe and damaging continuous operation in systems like elevators, causing loss of life and property.
Innovation Solution
A method involving the measurement and transformation of three-phase stator current to determine dual-axis current components, calculating angular velocity, and comparing its frequency with the inverter's output voltage frequency to detect faults, with additional time-based verification to avoid false positives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional fault detection methods are used, then the detection process is simple, but the detection speed and accuracy are insufficient leading to delayed fault identification
Solution Approach 1:
The patent transforms the detection approach by changing the parameter domain from time-domain analysis to frequency-domain analysis using Fast Fourier Transform (FFT). This parameter transformation enables accurate fault detection by analyzing frequency characteristics of current signals, resolving the contradiction between detection accuracy and method simplicity.
Solution Approach 2:
The patent replaces traditional mechanical or electrical test methods with a computational signal processing approach. By using mathematical transformations (FFT) and spectral analysis algorithms, the system achieves rapid and accurate fault detection without complex physical testing equipment.
2Reliability
If immediate fault detection is implemented, then system safety is improved, but false positives may increase causing unnecessary system shutdowns
Solution Approach 1:
The patent applies preliminary filtering actions by establishing frequency difference thresholds before actual fault detection. By pre-defining what constitutes a valid fault signal versus normal variation, the system可以避免 false positives while maintaining rapid detection capability.
Solution Approach 2:
The patent implements feedback mechanisms by continuously monitoring the frequency difference between angular velocity and output voltage, and only triggering fault detection when the difference exceeds predetermined thresholds for sustained periods. This feedback approach distinguishes true faults from transient anomalies.
Data Source
AI summary
A method of detecting a connection fault of an electric motor, applies to a driving mechanism of an inverter, and includes: measuring a three-phase stator current of the electric motor; transforming the three-phase stator current to acquire dual-axis current components in a stationary coordinate; calculating an angle of rotation of the electric motor according to the dual-axis current components; calculating an angular velocity according to the angle of rotation; comparing a frequency of the angular velocity with a frequency of an output voltage of the inverter; and determining that the electric motor occurs a connection fault if a difference between the frequency of the angular velocity and the frequency of the output voltage is greater than a predetermined frequency difference value.