Induction Motor Stator Turn Fault Detection Using Residual Impedance
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Solution Overview
Problem
Existing methods for detecting turn faults in AC induction motor stators are prone to errors due to variations in measuring equipment and environmental conditions, leading to inaccurate results.
Innovation Solution
A method that determines turn faults by calculating residual voltage and impedance, compensating for equipment variations and temperature changes, and using phasors to determine symmetrical components, thereby improving the accuracy of fault detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard measuring equipment (current transformers and potential transformers) is used to measure voltages and currents for turn fault detection, then the measurement process is simple and equipment cost is low, but measurement accuracy deteriorates due to variations in gain and phase delays
Solution Approach 1:
The patent transforms the measured voltages and currents into the synchronous reference frame (dq0 coordinates) and extracts symmetrical components (positive, negative, and zero sequence components). By changing the parameter representation from time-domain measurements to frequency-domain symmetrical components, the method eliminates the influence of gain and phase variations in the measuring equipment, thereby improving measurement accuracy without requiring additional calibration equipment.
Solution Approach 2:
The patent introduces an intermediary processing stage that uses the relationship between symmetrical components and sequence networks to eliminate measurement errors. The intermediate calculation of negative sequence voltage and current, combined with positive sequence values, serves as a mediator that compensates for equipment variations before final turn fault detection, resolving the contradiction between simple measurement and accurate results.
2Measurement precision
If environmental conditions are not compensated for, then the measurement process remains simple and fast, but detection accuracy deteriorates due to temperature and other environmental variations
Solution Approach 1:
The patent performs preliminary action by pre-calculating and storing the relationship between symmetrical components and turn fault indicators under various environmental conditions. During actual operation, the system directly applies these pre-established relationships to compensate for temperature and environmental variations, achieving accurate detection without time-consuming real-time environmental measurements or calculations.
Solution Approach 2:
The patent implements feedback by continuously monitoring the negative sequence voltage and current in the synchronous reference frame and comparing them against expected values based on positive sequence components. This feedback mechanism automatically compensates for environmental variations by detecting deviations caused by turn faults versus those caused by environmental changes, maintaining detection accuracy without increasing processing time.
3Measurement precision
If residual voltage and impedance calculations are performed to compensate for equipment variations, then measurement accuracy improves, but computational complexity increases
Solution Approach 1:
The patent segments the complex measurement problem into distinct computational stages: first transforming to synchronous reference frame, then calculating symmetrical components,接着 computing negative sequence values, and finally determining turn fault indicators. By dividing the computational process into modular segments, each with a specific function, the system achieves accurate compensation for equipment variations while keeping individual computational steps manageable and efficient.
Data Source
AI summary
A system and method are provided for correction of parameters used in determination of stator turn faults of an induction motor. An embodiment may include determining a residual impedance and/or a residual voltage of the motor, and correcting a normalized cross-coupled impedance based on the residual impedance and residual voltage. Additional embodiments may include measuring an operating temperature of the motor and determining a negative sequence impedance of the motor based on the temperature. Another embodiment may include measuring voltages and currents of the motor and determining phasors for the voltages and currents using compensation for variations from a nominal frequency of the motor.