Motor Winding Fault Detection via Inverter Harmonics
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Solution Overview
Problem
Conventional motor control systems fail to effectively detect winding faults in electric machines due to limitations in diagnostic techniques, particularly in analyzing information contained in inverter harmonics, leading to potential false alarms and inadequate detection of impedance changes.
Innovation Solution
A motor diagnostics system that employs inverter harmonics to evaluate sequence impedance by determining phasor values at predetermined harmonic frequencies, providing a higher signal-to-noise ratio and more robust fault detection through impedance estimation and processing of digitized voltage and current signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional diagnostic techniques are used to detect winding faults, then the system complexity is low, but the measurement precision and reliability of fault detection are insufficient
Solution Approach 1:
The patent extracts and analyzes specific inverter harmonics (5th, 7th, 11th, 13th order) from the complex PWM signal to detect winding faults. By focusing on these particular harmonic components rather than analyzing the entire frequency spectrum, the system achieves improved measurement precision while managing device complexity through selective signal extraction
Solution Approach 2:
The patent uses sequence impedance calculation as an intermediary parameter to detect winding faults. Instead of directly detecting physical winding degradation, the system measures voltage and current harmonics, calculates sequence impedance values, and uses these impedance changes as an intermediate indicator of winding health, thereby improving detection precision
2Reliability
If conventional diagnostic techniques are used, then the device complexity is low, but the reliability of fault detection is insufficient leading to false alarms
Solution Approach 1:
The patent implements a feedback mechanism where sequence impedance values calculated from harmonic analysis are continuously monitored and compared against threshold values. This feedback loop enables the system to adaptively detect winding faults with higher reliability, reducing false alarms by confirming impedance changes exceed predetermined thresholds before triggering fault indications
Solution Approach 2:
The sequence impedance serves as an intermediary that translates complex harmonic signal patterns into a single reliable metric for fault detection. By using impedance as the intermediary parameter, the system achieves more reliable and interpretable fault detection results compared to direct harmonic magnitude analysis
3Measurement precision
If inverter harmonics are analyzed for fault detection, then the measurement precision is improved, but the difficulty of detecting and measuring increases
Solution Approach 1:
The patent replaces complex mechanical/wiring-based diagnostic methods with electrical harmonic analysis. By substituting physical inspection and measurement methods with electrical signal processing of inverter harmonics, the system achieves superior measurement precision for detecting winding impedance changes while the computational complexity is managed through standardized calculation procedures
Data Source
AI summary
A controller for driving a motor includes a multiphase driver, an analog-to-digital converter (ADC), impedance estimation circuitry, and fault detection circuitry. The multiphase driver is configured to generate drive signals for energizing each motor phase winding. The ADC is configured to digitize voltage and current from each motor phase winding. The impedance estimation circuitry is configured to determine a phasor value for the digitized voltages and for the digitized currents at a predetermined harmonic frequency, and to determine a sequence impedance value based on the phasor values. The fault detection circuitry is configured to identify a fault in the windings of the motor based on the sequence impedance value.