Abstract: A data acquisition and processing system based on LabVIEW for testing the performance parameters of submersible motors was developed. This system can automatically acquire, analyze, and process the performance parameters of submersible motors, as well as display, store, and print out the test data. The successful application of the system has greatly reduced the labor intensity of workers and improved work efficiency. Keywords: Submersible motor; Data acquisition; Performance curve; LabVIEW 1 Introduction Submersible motors are the power components in submersible electric pump units, and their operating characteristics directly affect the normal operation of the entire unit. With the needs of production development, the variety and output of motors are increasing, and the workload of routine testing is also constantly increasing, but testing methods are relatively lagging behind. Currently, the application of submersible electric pump units abroad is represented by the United States, where the testing technology for submersible motors has been developed relatively well, enabling the provision of accurate performance curves along with the units to users. In China, only a few large electric pump manufacturers can conduct dynamometer tests on submersible motors, but these are limited to measuring some basic parameters and cannot directly and accurately plot the five characteristic curves of the motor. To this end, we jointly developed a rodless pump dynamometer system with Shengli Oilfield Rodless Pump Company. This system is based on NI's software development platform LabVIEW and hardware platform. After testing, the system has met the requirements of automated testing and accurate plotting of submersible motor performance curves. 2 Design of the test system The system design includes two parts: hardware and software. 2.1 System hardware design The system hardware design includes three parts: test bench, operation control console, and data acquisition card selection. (1) Test bench The test bench consists of a gearbox, a loader (including a DC generator and an adjustable high-power resistive load), a torque and speed sensor, a connection conversion mechanism, and a test frame. See Figure 1 for its physical diagram: [align=center] Figure 1 Physical diagram of the dynamometer[/align] (2) Operation control The operation control part is divided into a submersible motor low-voltage control cabinet (on a Class B platform), a high-voltage control cabinet, a generator excitation power supply, a resistance test cabinet, and an operation control console. Other auxiliary parts include signal conversion interface boxes, junction boxes, shielded cables, etc. To prevent mutual interference, high-voltage and low-voltage lines are routed separately, and hardware and software filtering is performed according to the actual situation to ensure the authenticity of the obtained signals. The planar block diagram of the submersible motor test device system is shown in Figure 2: [align=center] Figure 2 Planar block diagram of the submersible motor test device system[/align] (3) Data acquisition part The data acquisition system uses Advantech's industrial control computer as the main body to realize the sequential control, data acquisition, data processing, data storage, test curve plotting, printing and other functions of the test system. The motor current, voltage, torque, speed and other parameters that need to be measured in the system are transmitted to the measuring instrument for real-time display by each sensor. A 250Ω precision resistor is connected in series at the transmitter output terminal of the instrument and then the instrument outputs a DC voltage of 1~5V through secondary transmission. The data acquisition card collects the analog signals of each parameter through different channels and converts them into digital signals for input to the industrial control computer. The corresponding sensor's transmission formula is used to convert them into the instantaneous values ​​of each parameter. ① Selection of data acquisition card The data acquisition card selected in the system is the PCI-1713 from Advantech. It is a 32-channel isolated analog input card with the following characteristics [1]: a. It has 32 single-ended inputs or 16 differential inputs, which meet the requirements of the 6 measurement parameters of this system, and at the same time leaves a certain expansion margin. b. It has a 12-bit A/D converter with high conversion accuracy and a conversion time of 2.5μs. c. The sampling frequency can reach 100KHz, which can reflect the changes in system parameters in real time. d. The channel gain is programmable. Signals from the field will always contain various interference components, especially common-mode interference (mainly caused by the ground potential of the data acquisition card PCI-1713 and the ground potential of the signal source not being completely equal). The differential input of analog quantities uses a differential amplifier to eliminate the common-mode interference of analog quantities. If the signal source is relatively clean, the single-ended input method can be used [2]. In view of the characteristics of this system, the differential input mode is adopted, and its analog input signal connection method is shown in Figure 3. [align=center]Figure 3 Differential Input Connection Diagram[/align] In the figure, Vs is the analog signal to be measured, and Vcm is the common-mode voltage between the analog signal ground and the PCI-1713 ground. ② Relay Card Selection The relay card used is Advantech's PCL-735 board. The PCL-735 is a relay output card used for device on/off control or signal switching. This card provides 12 electromechanical SPDT relay outputs. The on/off status of each relay is very easy to monitor. There is a red LED indicator next to each relay, which shows the on/off status of the relay. The card has a DB-37 interface for easy signal connection between the board and the device. It is a relatively mature product from Advantech, characterized by reliability, fast switching response, and ensuring timely and reliable power input. ③ Selection of Torque and Speed ​​Sensor Torque and speed sensors are widely used, but traditional torque sensors typically employ resistance strain gauges to detect torque signals and conductive slip rings to couple power input and strain signal output. Since conductive slip rings involve frictional contact, wear and heat generation are inevitable. This not only limits the rotational speed of the rotating shaft and the lifespan of the conductive slip rings, but also inevitably causes fluctuations in the measurement signal and increases in error due to unreliable contact. Therefore, how to reliably couple energy and signals on a rotating shaft has become the most challenging problem for torque sensors. The JN338 digital torque and speed sensor cleverly solves this problem. Therefore, the JN338 torque sensor is selected for this system. The JN338 is a product of Beijing Sanjing Venture Group Co., Ltd. This sensor uses two sets of special toroidal rotary transformers to achieve energy input and torque signal output, thus solving the problem of reliable energy and signal transmission between rotating and stationary parts in a rotating power transmission system. This sensor can also simultaneously measure the rotational speed of the rotating shaft, allowing for convenient calculation of the shaft output power. Therefore, this sensor can achieve multi-parameter output of torque, speed, and shaft power. 2.2 System Software Design The system uses LabVIEW as the programming platform, which is a development environment based on the graphical programming language G. LabVIEW integrates all the functions of communication with hardware such as GPIB, VXI, PXI, RS-232 and RS-485 standard interfaces and data acquisition cards. It also has built-in library functions that facilitate the application of software standards such as TCP/IP and ActiveX. Using LabVIEW as the development platform, the software programming is convenient, simple and efficient; the graphical interface is user-friendly, the operation is simple and the human-computer interaction is strong; it can be easily connected to peripherals and print output; it has good compatibility and can replace high-performance data acquisition cards at any time to improve the performance of the instrument [3]. The test system developed with LabVIEW mainly includes five parts: system self-test, data acquisition, data processing, printing test reports and help, etc. Among them, the system self-test mainly tests the communication between the computer and the hardware; the data acquisition part mainly sets the test conditions, sensors and acquisition parameters, performs real-time data acquisition and display, and saves the acquired data into a data file; the data is stored in the form of a table. In order to facilitate future query, it can be stored by test date and motor model. Data processing mainly involves various post-processing steps on the saved data files; the printing section involves editing and printing test reports; and the help section includes real-time help and user manuals. 3. Anti-interference Design During resistance measurement, the original scheme (measuring the voltage across the coil at the moment the motor induction coil disconnects) was prone to generating sharp pulses that could damage the circuit board. Therefore, a capacitor and a protection module were added to the design to completely shield the harmful sharp pulses and protect the circuit board. Furthermore, since both the submersible motor under test and the generator acting as the load are high-voltage driven, electromagnetic interference to various test signals is significant at the test site. During actual data acquisition, due to external environmental interference, the less-than-ideal performance of the acquisition card and other hardware circuits, and data quantization factors, the acquired signals will contain varying degrees of noise. Therefore, to obtain more accurate measurement results, necessary noise processing is crucial. For noise in different frequency bands from the useful signal, filtering methods can effectively remove it. In terms of software filtering, median filtering was used based on the system's on-site operating conditions, employing the most advanced point-by-point filtering technology, resulting in faster and smoother data change response. 4 Data Acquisition and Processing of Dynamometer Test Motor testing mainly studies the testing of various characteristics and parameters of motors. Including the working characteristics and mechanical characteristics of motors[4]. Therefore, the motor testing system mainly realizes the following functions: ① No-load test ② Locked test ③ Motor efficiency, power factor and slip test. The parameters that need to be measured during motor testing are DC resistance, copper loss, iron loss and mechanical loss during no-load process, locked current and torque during locked test, and input power Pmi, stator current I1, efficiency ηm, power factor cosΦ and slip Sref and output power Pmu relationship curve of motor under rated voltage and rated power during load test. The original test method is that the tester first records the various data measured during the test, and then the data is processed by the specialists, and then the curve is drawn by plotting points. This method is not only time-consuming and laborious, but also many results are obtained from the curve, so some subjective factors will cause a lot of errors. The LabVIEW-based motor dynamometer testing method not only automates the entire testing process but also boasts powerful data processing capabilities. After measurement, a simple click of the data processing button completes all data processing, including curve plotting. Furthermore, three curve fitting methods are available: linear, polynomial, and exponential. Users can choose the fitting method according to their needs. Figure 4 shows the no-load test interface. For easy future reference, the data and curves can be saved in Word format. [align=center] Figure 4 No-load test interface[/align] 5. Author's Innovation The successful operation of the system solves the problems of outdated on-site testing methods, large measurement errors, and high operator workload. It features stable operation, good real-time performance, high accuracy, simple operation, and a user-friendly interface, making it a highly valuable testing device for submersible motor performance parameters. References: [1] PCI-1713 32-channel isolated Analog Input Card User' Manual. [2] Li Ren. Electrical Control [M]. Beijing: Machinery Industry Press. 1990 [3] Gary W. Johnson, Richard Jennings. LabVIEW Graphical Programming [M]. Beijing: Peking University Press. 2002 [4] Li Tiangang. Implementation of Stall Test of Submersible Generator and Solution of Related Problems [J]. Research and Discussion on Technical Supervision of Petroleum Industry, Vol. 18, No. 7, 2002. [5] Zhu Yuqing, Wu Weibin, Hong Tiansheng. Fuzzy Control System for Diesel Engine Injection Quantity Based on Virtual Instrument [J]. Microcomputer Information, 2006, 3-1: P24-26