Jiangsu Huayu Electric Co., Ltd , https://www.huayutransformer.com
Introduction
Note: For fixed displacement compressors, the displacement per revolution is multiplied by 10.
Trisun New A/C Compressor Evaluation Tester for Types of Compressor and Valve (CETM)
Model NO.: CETM
HS Code: 90262090
Model NO.: CETM
HS Code: 90262090
2018 Upgrade – A/C Testing with New Software System
The A/C Compressor Evaluation Test Machine (CETM) is designed to evaluate compressors without requiring the operator to have in-depth knowledge of compressor design or functionality. The 2017 updated CETM was developed for compressor manufacturers and remanufacturers, offering increased automation and enhanced testing capabilities. This machine simulates the real-world loads that a compressor would experience in an actual vehicle air conditioning system.
To operate the CETM, a computer must be equipped with the TDS Compressor Evaluation Software (TCES). While a preloaded list of compressor models is available for convenience, the system can test any compressor as long as the pulley diameter and displacement per revolution are provided. It’s not necessary to know whether the compressor is fixed or variable—this is automatically detected by the machine, which then runs the appropriate test for either type.
Quick Start
Using the CETM is straightforward. Begin by mounting the compressor on the universal bracket, aligning it with the pulley, and ensuring the belt is straight. The compressor should be properly oiled, and any excess oil drained. Connect all hoses carefully. While measuring the crankcase pressure isn’t mandatory, it can be helpful for diagnostics.
Start the software and confirm that the machine communicates with the computer. This is indicated by the DL405 PLC Communications panel changing from red to green.
The software features three main screens:
Variable Animation Screen – This screen provides an internal view of a generic variable displacement compressor. When the left-side animation is active, it indicates minimum displacement, while the right-side animation shows full displacement. Real-time pressure values are displayed at the bottom of the screen.
Setup Screen – Calibration settings for inputs are shown here. These are factory-set and should not be altered. The test duration is also set at the factory. The drive motor can run forward or backward, though most compressors require forward operation.
The easiest way to start a test is to use the drop-down list in the "Select Compressor Type" field. Choose the model that best matches the one being tested, then click "OK."
Custom lists can be created to automatically populate reports. Use the provided text file, TheList.txt, located in C:/TDS/, and modify it using a text editor like Notepad. Ensure the format is maintained, and the last line must be "None,0,0,0,0."
Example format:
Once a custom list is loaded, the default list will be unavailable until the program restarts. Add your list by clicking the "" button next to the drop-down menu.
Performance Report Screen – After selecting the compressor type, navigate to the Performance Report screen to enter the clutch diameter in millimeters. Ensure the compressor is properly aligned using the universal test bracket, then press the "Start" button.
Once the test is complete, press the "Print" button on the Setup screen to generate the report and save the data to disk.
Theory of Operation
An automotive air conditioning compressor functions as a pump that circulates gas through a closed system. There are various types and sizes of compressors, and the CETM is designed to test them all. By entering the displacement per revolution and pulley diameter on the Performance Report screen, the system adjusts the drive motor speed accordingly, ensuring consistent test results across different compressor models.
During the test, the system mimics real-world conditions. When the test starts, current is sent to an air pressure transducer that sets the suction pressure to around 3 bar. This pressure is high enough to simulate a medium to high heat load on the evaporator and prevents freezing. If the compressor is variable, the internal control valve should be factory-set to match the crankcase pressure with the suction pressure.
The suction pressure is then reduced to simulate a low heat load or freezing evaporator temperature. If the compressor is variable, the discharge pressure should drop significantly. When the suction pressure increases again, the discharge pressure should rise accordingly. For fixed displacement compressors, the discharge pressure drops proportionally to the suction pressure.
Discharge pressure is controlled by an adjustable orifice inside a metering valve. The pressure drop across the orifice is directly proportional to the mass flow rate. When the compressor reaches minimum displacement, the mass flow rate decreases. The metering valve is pre-set at the factory to achieve the desired maximum discharge pressure, which can be adjusted if needed. However, changes to this valve may require adjustments to the "Peak" setting on the Performance Report screen.
The "Peak" setting represents the maximum pressure differential a good baseline compressor should achieve. Setting it too low might allow poor-quality compressors to pass, while setting it too high could cause good ones to fail. This setting is crucial and should be handled with care.
The CETM includes a frequency inverter to adjust the drive motor speed. This inverter also sends power usage data to the computer, helping to prevent excessive power consumption that could reduce the motor's lifespan.