Development Of Pump Characteristic Test System In Frequency Conversion Condition

Pump is widely used as a general-purpose machine which electricity consumption is about 17% of the national electricity consumption.Due to the complicated flow phenomena in flow pump,pump performance test is still the most effective method to improve the technology of pump.With the wide application of frequency conversion technology in pump energy-saving,pump performance test in frequency conversion conditions is more and more important.At present,the pump performance parameters in frequency conversion conditions are generally obtained by the use of similarity theory in normal frequency test.But the similarity error and harmonic interference make final data quite different ??to the actual data.Through the analysis of typical pump performance test system.The results show that there are few systems which used to measure the pump performance parameters in frequency conversion conditions.With the development of Internet technology,the data-sharing of traditional pump characteristic test system needs to be further developed and perfected.Aiming at these problems above,experimental research,theoretical calculation,circuit simulation and other methods are used to develop a pump characteristic test system which can measure pump performance parameters in frequency conversion conditions and the information sharing degree is very high.Finally,experimental program is designed to verify the system.The main research content,conclusions and innovations are as follow:1.To study the influence of frequency harmonics on the pump performance parameters,the related signals of the pump performance parameters are collected in frequency conversion conditions.According to the data analysis,the voltage harmonic distortion rate reaches about 149% and the harmonic interference amplitude of the pressure signal reaches about 52% in frequency conversion conditions.When the filter with the cutoff frequency of 100 Hz is set to treat the harmonic,the voltage harmonic distortion rate reduced to about 3% and the harmonic interference amplitude of the pressure signal reduced to about 5%.2.To solve the problem of measuring pump performance parameters in frequency conversion conditions,embedded design of the system is conducted based on the results of experiment above which is developed in the following aspects:(1)To measure the three-phase power conversion,inlet and outlet pressure and flow measurement in frequency conversion condition.In the aspect of hardware circuit design,low-pass filter,?-type filtering circuit are designed to perform the filtering on the signal collected in the variable frequency operation condition,In the aspect of software design,filter algorithm is designed to improve interference ability of the system.(2)To measure the motor speed in frequency conversion condition,a new scheme is proposed which combined induction coil and power chip acquisition in the aspect of hardware circuit design.The stator frequency of the motor is obtained from the chip and the rotor frequency is obtained from the induction coil.According to the calculation formula,the motor speed can be obtained from stator and rotor frequency.In the aspect of software design,sliding filter algorithm is designed to improve interference ability of the system.(3)To improve operation efficiency of the system,a time scheduling scheme is designed which encapsulate the corresponding programs of each module into subroutines.The logic and duration of program execution are designed according to the complexity and priority of program in order to make the RAM of MCU reasonably used.3.To improve the degree of data-sharing,this paper designs three data transmission modes: an industrial screen interaction terminal,a host computer,an Android client which Not only improve the degree of data-sharing,but also realize real time state monitoring of pump.4.Finally,the prototype of system is developed and the test bench is set up to verify the system.By analyzing a series of data,the errors of the pump performance parameters collected between two systems are all less than 0.5% which meets the national pump performance test standards.