Power supply test system with PF series digital power meter as the core

    Abstract: This article focuses on the application of Yuanfang PF series digital power meters in various power supply tests, and briefly introduces its main measurement principles and technical indicators.

   Keywords: Digital power meter, power supply test, harmonic analysis, power factor, non-sinusoidal wave measurement

1 Introduction

    With the rapid development of electronic technology, modern electronic equipment plays an increasingly important role in various application fields, and modern electronic equipment is extremely dependent on the power supply that provides its "food". This requires power supply manufacturers and quality supervision departments to strengthen testing of power supply quality. Based on international advanced instrument technology, Hangzhou Yuanfang Instrument Co., Ltd. has independently developed and produced PF series digital power meters in the production lines and laboratories of manufacturers of household appliances, motors, power tools, electric heating appliances, lighting appliances, transformers, and welding machines. It has been widely used in , quality inspection departments and standard measurement departments, and can also become a powerful tool for various types of power supply testing.

2 Typical power supply test system

    Figure 1 is a schematic diagram of a typical power supply test system. As can be seen from the figure, the power supply under test, digital power meter, voltage regulator and load constitute a typical power supply test system. The mains power is connected to the input terminal of the power supply under test through the voltage regulator, and the load is connected to its output terminal. . The digital power meter is connected in parallel with the voltage sampling sensor V and in series with the current sampling sensor A in its input and output circuits respectively. The following introduces the typical applications of Yuanfang PF series digital power meters in several common power supply tests.

2.1 UPS test

    UPS can not only ensure "uninterrupted power supply" when the power grid fails, but also can eliminate grid clutter, suppress grid voltage fluctuations, and significantly improve power supply quality. Therefore, it has been rapidly popularized and developed in recent years. With the expansion of application scope, more and higher requirements have been put forward for UPS performance indicators. Typical technical indicators of UPS, such as input AC voltage, input frequency, power factor, output rated capacity, power factor, output voltage, output current, output frequency, overload capacity, etc., can ensure the power supply quality of UPS. However, the loads of UPS are mostly various types of computers, electronic instruments and electronic equipment, etc. Most of these equipment are non-linear loads, and the UPS itself absorbs energy from the power grid, and as a load of the power grid, it is also non-linear. Since the current waveform of non-linear loads is seriously distorted, the peak ratio and total harmonic distortion of the waveform are important technical indicators that must be examined for UPS. For the measurement of non-linear loads with severely distorted waveforms, it is difficult for ordinary electrical instruments to accurately measure. Yuanfang PF series digital power meters use advanced modern sampling and computer technology to accurately measure non-sinusoidal waves, especially the harmonic analysis in this series. The instrument can perform harmonic analysis continuously, quickly and accurately.

2.2 Testing of variable frequency power supply and inverter power supply

    Variable frequency power supplies and inverter power supplies are increasingly widely used in various industries, and both generally include DC/AC inverters. There are many ways to construct a DC/AC inverter. However, how DC/AC outputs high-quality sine waves is crucial. The harmonic content in its output voltage waveform has attracted more and more attention, especially in the power supply design process. In this process, how to measure and control the harmonic content of each order has become the key technology. Yuanfang PF series digital power meter has powerful harmonic analysis function, which can directly display the total harmonic distortion and each harmonic value. It can also print out or connect to a computer to obtain the harmonic analysis results.

2.3 Testing of AC stabilized power supply

    There are many types of AC stabilized power supplies and they are widely used, and their voltage stabilization principles are also different. There are parameter adjustment type, auto-adjusting type, high-power compensation type, switching type, etc. However, their input voltage range, input side current distortion, Source power factor, output waveform, load adaptability, voltage stabilization accuracy, overall machine efficiency, output frequency, etc. are all electrical performance indicators that must be examined. The AC power analyzer in the Yuanfang PF series digital power meter simultaneously analyzes and detects the input and output parameters of the power supply. It has a harmonic analysis function, can display the measurement results directly from the panel, and can also print or communicate measurement data and waveforms. It is the best choice for AC power supplies. Ideal testing tool.

2.4 Testing of switching power supplies

    The rapid development of power electronic technology has promoted the rapid development of switching power supplies, especially high-frequency switching power supplies. Switching power supplies have been widely used in fields such as electric vehicles and variable frequency drives. Power factor and overall machine efficiency are important parameters that must be examined for switching power supplies. Using power factor correction technology to improve the input power factor of switching power supplies can reduce harmonic pollution to the power grid. Yuanfang PF series digital power meter has powerful measurement and data calculation functions, can accurately measure the power factor of non-sinusoidal waves, and also has the function of harmonic distortion measurement, which is a good helper to help improve the power factor of switching power supply.

2.5 Testing of electronic transformers

    Electronic transformer is a common power supply device because it is simple, practical and has a large market demand. For electronic transformer manufacturers, it is necessary to quickly and effectively test the input and output parameters of the transformer on the mass production line and eliminate unqualified products. The transformer-specific tester in the Yuanfang PF series digital power meter is developed based on this demand. This transformer-specific tester can simultaneously test the primary and secondary electrical parameters of the electronic transformer, and automatically convert the no-load test voltage of the transformer. and load electrical parameters, and automatically determines whether the transformer is qualified or not according to the electrical parameters set by the user, and issues an audible and visual alarm. After setting the measurement conditions, this special tester can complete all testing and judgment work of an electronic transformer by just pressing a test button. It is a powerful assistant for mass production of electronic transformers.

3 PF series digital power meter measurement principle

    Yuanfang PF series digital power meters have various varieties and complete functions. They mainly include single-phase series, three-phase series and special series. The following takes a single-phase digital power meter as an example to illustrate the typical measurement principles of Yuanfang PF series digital power meters.

3.1 Schematic diagram

    The instrument mainly consists of input part, single-chip computer, display and interface parts, as shown in Figure 2. In the voltage input circuit, the input voltage is program-controlled amplified after passing through the voltage divider, and is sent to the A/D converter after passing through the sample and hold device. The conversion result is placed in the voltage buffer. In the current input circuit, the current is converted into a voltage signal by the current-to-voltage converter, and then amplified by program control. After passing through the sample and hold device, it is sent to the A/D converter, and the conversion result is placed in the voltage buffer. The single-chip computer reads the waveform data from the buffer and performs data processing. Automatic range switching, data calculation, display and output control are also completed by the single-chip computer.

    Through the serial communication interface, the instrument can also provide rich data to the host computer, such as sampling waveform data, various measurement and calculation results, harmonic analysis results, etc. Based on these data, the host computer can easily organize its own test system as needed, such as displaying or outputting measured waveforms, harmonic spectrum, etc., or processing together with data provided by other test equipment.

3.2 Main technical indicators of the instrument

    Accuracy: 0.5% ~ 0.03%

    Measuring range:

    Voltage: (0~600)V;

    Current: (0～100)A;

    Frequency: from DC, 10Hz to 500kHz.

3.3 An example of actual measurement report

    Figure 3 shows the test report printed by the PF9832 AC power analyzer after testing an AC regulated power supply.

4 Conclusion

    Yuanfang PF series digital power meters range from 0.5% accuracy to 0.03% accuracy achieved by 16-bit high-speed A/D, from DC to AC500kHz, from affordable models with basic functions to multi-functional models, Yuanfang PF series digital power meters provide users with more Lots of choices. The successful application of Yuanfang PF series digital power meters in multiple systems also proves that it can meet the scientific research, production, and quality inspection needs of various power equipment, and is the core tool that forms the power supply test system.