Individual Phase Resistance Estimation in Electric Motors
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Solution Overview
Problem
Classical methods for online motor resistance identification cannot distinguish individual phase resistance, only providing an equivalent average value.
Innovation Solution
A method involving an adjustable speed drive (ASD) that injects DC currents at different phase angles, determines output voltages and currents, extracts DC components, and calculates individual phase resistance, allowing for the estimation of asymmetrical motor resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If classical symmetrical detection methods are used to measure motor resistance, then the measurement process is simple, but only an equivalent average resistance value can be obtained without individual phase resistance information
Solution Approach 1:
The patent segments the measurement process by injecting DC currents at different phase angles (0°, 120°, 240°) to separately identify each phase resistance. Instead of measuring all phases simultaneously with a single average value, the method divides the measurement into distinct phase-specific measurements, enabling individual phase resistance detection while maintaining a systematic approach.
Solution Approach 2:
The patent changes the measurement parameters by varying the DC current injection phase angles. By injecting currents at different angular positions (0°, 120°, 240°) and analyzing the resulting voltage and current measurements, the method transforms a single average resistance measurement into multiple phase-specific resistance values through parameter variation.
2Measurement precision
If DC current injection is performed at multiple phase angles to identify asymmetrical resistance, then individual phase resistance can be determined, but the measurement time and number of injections increase
Solution Approach 1:
The patent employs periodic action by injecting DC currents at regular phase angle intervals (0°, 120°, 240°). This periodic injection pattern allows the system to systematically measure each phase while maintaining a structured timing sequence, enabling complete phase resistance identification through repeated periodic measurements at different angular positions.
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
Improves motor control and stability, particularly in high-performance applications, by accurately determining phase resistance, enabling predictive maintenance and detecting potential faults or malfunctions.
Implementation Method 1
extracting DC components present in the determined output voltages and currents
Implementation Method 2
calculating the cumulated output resistance Rs seen by the ASD on each phase of the motor individually
Data Source
AI summary
The present invention relates to a method for estimating individual phase resistance of a motor by means of an adjustable speed drive (ASD) while the motor controlled by the ASD is running and/or is at standstill. The motor is an asynchronous motor or a synchronous motor. The invention also relates to an adjustable speed drive for executing a corresponding method.