Electric Compressor Leakage Current Test Segmentation
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Solution Overview
Problem
Testing the leakage current of electric compressors is inefficient and inaccurate due to the long time required for convergence, especially when products are exposed to dielectric coolants and lubricating oils, which prolong the charging process and reduce test efficiency and accuracy.
Innovation Solution
A method involving multiple test processes with different time frames and reference current values is implemented, where a first test determines products with low current values as acceptable, and subsequent tests refine those with higher values, reducing overall test time while maintaining accuracy, using regression analysis to set predictive and acceptance reference current values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a DC voltage is applied to the dielectric and the total current is measured after 10 minutes to ensure accurate leakage current measurement, then the measurement precision is improved, but the loss of time increases significantly
Solution Approach 1:
The patent divides the leakage current test into two distinct stages: a first test stage that runs for a shorter duration (e.g., 1 minute) and a second test stage that runs for the full duration (e.g., 10 minutes). This segmentation allows most products to be quickly screened in the first stage, while only potentially problematic products undergo the complete second stage test, thereby reducing overall test time while maintaining measurement accuracy for critical cases.
Solution Approach 2:
The patent applies partial action by conducting a shortened first test (e.g., 1 minute instead of 10 minutes) for initial screening. This partial test is sufficient to identify clearly defective products, while products that pass the first test are subjected to the complete second test. This approach avoids applying the full 10-minute test duration to all products, thus reducing total test time while preserving accuracy where needed.
2Productivity
If the test time for each product is reduced to improve test efficiency, then the productivity is improved, but the measurement precision deteriorates
Solution Approach 1:
The patent segments the testing process into two stages with different durations and purposes. The first stage uses a shorter test time (e.g., 1 minute) for rapid screening of most products, improving overall productivity. The second stage uses the full test time (e.g., 10 minutes) only for products that fail or are borderline in the first stage, ensuring measurement precision is maintained for critical evaluation.
Solution Approach 2:
The patent applies partial action by using a reduced test duration (e.g., 1 minute) for the majority of products in the first stage, which is sufficient for initial screening. This partial testing approach significantly improves productivity compared to testing all products for the full duration, while the complete second stage test ensures accuracy when needed.
3Measurement precision
If a high capacitance capacitor is charged to the setting voltage to test leakage current, then the test can be performed, but the charging time becomes excessively long
Solution Approach 1:
The patent segments the leakage current test into two stages: a first stage with a shorter charging and testing period (e.g., 1 minute) and a second stage with the complete charging and testing period (e.g., 10 minutes). This segmentation allows rapid initial assessment without requiring full charging time, thereby reducing the time penalty associated with high capacitance components while maintaining the option for accurate measurement when necessary.
Solution Approach 2:
The patent applies partial action by conducting a shortened first test (e.g., 1 minute) that does not require full charging of high capacitance components. This partial approach avoids the excessively long charging time that would be required if the full test duration were applied to all products, thereby improving productivity while the second stage ensures accurate measurement capability is preserved.
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
This approach significantly reduces the total test time for electric compressors while maintaining the same level of accuracy as a 100% test using a single acceptance reference current value, ensuring that only acceptable products are classified correctly.
Implementation Method 1
Freon-based coolant and ether-based or ester-based lubricating oil which are commonly used are dielectrics, and hence, a leakage current from the coil to the housing through the coolant or the lubricating oil is likely to be generated.
Implementation Method 2
The total current I decreases according to a change in the absorption current Ia, gradually the decrease becomes slow, decreases until influence of the absorption current Ia disappears, and finally converge to the leakage current IL.
Data Source
AI summary
According to the present invention, after a predetermined voltage is applied to a coil in a state in which the inside of an electric compressor is filled with dielectric liquid and the coil of a motor is immersed in the dielectric liquid, in a first test process, a test product in which a current value when a first predetermined time T1 elapses I1 is less than or equal to a first reference current value is determined as an acceptable product, in a second test process, among the test products in which the current value is greater than the first reference current value in the first test process, a test product in which a current value I2 when a second predetermined time T2 longer than the first predetermined time elapses is less than or equal to a second reference current value is determined as an acceptable product, a test product in which the current value is greater than the second reference current value is determined as a disqualified product, and the first reference current value is a predictive reference current value that allows a test product which is to be determined as a disqualified product in the second test process to be determined as a disqualified product in the first test process, and allows some test products which are to be determined as an acceptable product in the second test process to be determined as a disqualified product in the first test process.