Screw Compressor Power Detector Technology

Air compressor is a kind of machinery of generating and delivering compressed air, while the screw compressor has attracted more attention in gas industry. It has been widely used in industry, agriculture and other fields because of its simple structure, low cost and easy maintenance. As the compressor is often run in long-term and continuous mode, it has more power consumption than other electrical equipments. We can see that it's very significant for energy-saving project to study the power characteristics of screw compressor.Based on the background, we build up mathematical model for the working process of screw compress in this paper. Making tooth space as research object, we found the microscopic properties such as temperature and pressure in that space, and on the basis of that, we can found the macroscopic properties such as shaft power of the screw compressor by using the laws of thermodynamics. In addition, we analyse the difference of theoretical and actual power consumption. The detection of shaft power is based on the Fourier transform of one windowed signal, and we use an interpolation algorithm to correct the result.The system consists of the PM motor, screw compressor, sensors, data acquisition card and computer. We collect voltage and current signals by the LV25-P and LT308-S7, and the data is converted to standard signals before sent to the computer displaying on the VB interface. First, the data should be filtered by an improved filtering algorithm, and then we add the B-H window and do the FFT algorithm on that data. To improve efficiency, we write the FFT algorithm in C language and create a dynamic link library called in VB. At last we obtain the power curve under different conditions and analysis the power variation under different exhaust pressure. We can see that the conclusion is consistent with theoretical analysis which shows the system performances good and can be used as an industrial practice.This project has been used in the test of screw air compressor in a company, Suzhou. The test system has good accuracy and real-time, and it achieves the desired results. We can do further research and extension in the future.