Compressor Motor Current Diagnosis via Dual Threshold Segmentation
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Solution Overview
Problem
Existing compressors cannot differentiate between abnormalities in the compressor itself and abnormalities in the power supply system based on changes in motor current values, leading to incorrect diagnoses.
Innovation Solution
The compressor incorporates a control device that measures current values at specific times after motor startup and compares them to threshold values, distinguishing between compressor abnormalities and power supply system abnormalities through different notification modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the compressor uses a single threshold value for current drop time diagnosis, then the diagnosis method is simple, but it cannot differentiate between compressor abnormalities and power supply system abnormalities
Solution Approach 1:
The patent divides the current drop time diagnosis into two distinct time measurements: first time (t1) from motor start until current reaches first threshold value (I1limit), and second time (t2) from motor start until current reaches second threshold value (I2limit). By comparing both t1 and t2 against their respective thresholds, the system can differentiate between compressor abnormalities (both times exceed thresholds) and power supply abnormalities (only t2 exceeds threshold), thus resolving the contradiction between diagnostic simplicity and accuracy.
2Reliability
If the compressor determines abnormality based on drop time exceeding upper limit, then the diagnosis covers all cases of extended drop time, but it incorrectly identifies power supply system abnormalities as compressor abnormalities
Solution Approach 1:
The patent introduces an intermediary diagnostic approach using dual threshold comparisons. Instead of directly attributing extended drop time to compressor failure, the system uses two current thresholds (I1limit and I2limit) as intermediaries to indirectly identify the abnormality source. By checking whether current exceeds I1limit at time t1 and I2limit at time t2, the system can distinguish between compressor issues (both conditions fail) and power supply issues (only second condition fails), improving both reliability and precision.
Data Source
AI summary
A compressor includes a compressor body, a motor, a current sensor that detects a current value of the motor, and a control device that controls the drive of the motor, and the control device computes, through the current sensor, a current value (I1) of the motor at a point in time when first time has elapsed from the start of the motor and a current value (I2) of the motor at a point in time when second time longer than the first time has elapsed from the start of the motor, and makes a notification in a different mode.