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

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 highly dependent on the power supply that provides its "food". This requires power supply manufacturers, quality supervision departments, etc. to strengthen the detection of power supply quality. Hangzhou Yuanfang Instrument Co., Ltd., based on international advanced instrument technology, has independently developed and produced PF series digital power meters, which have been widely used in production lines, laboratories, quality inspection departments and standard measurement departments of manufacturers of household appliances, motors, power tools, electric heating appliances, lighting appliances, transformers, welding machines, etc., and can also become a powerful tool for various power supply tests.

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, the digital power meter, the voltage regulator and the load constitute a typical power supply test system. The mains power is connected to the input end of the power supply under test after passing through the voltage regulator, and the load is connected to its output end. The digital power meter is connected in parallel to the voltage sampling sensor V and in series to the current sampling sensor A in its input and output circuits respectively. The following introduces the typical applications of the Yuanfang PF series digital power meter in several common power supply tests.

2.1UPS Testing

UPS can not only ensure "uninterrupted power supply" when the power grid fails, but also eliminate grid clutter, suppress grid voltage fluctuations, and significantly improve the power supply quality. Therefore, it has been rapidly popularized and developed in recent years. With the expansion of the scope of application, more and higher requirements have been put forward for UPS performance indicators. Typical technical indicators of UPS, such as AC voltage, input frequency, power factor at the input end, rated capacity, power factor, output voltage, output current, output frequency, overload capacity at the output end, can ensure the power supply quality of UPS. However, the loads of UPS are mostly various computers, electronic instruments and electronic equipment, etc. These devices are mostly non-linear loads, and UPS itself draws 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 seriously distorted waveforms, ordinary electrical instruments are difficult to measure accurately. Yuanfang PF series digital power meters use advanced modern sampling and computer technology to accurately measure non-sinusoidal waves, especially the harmonic analysis instruments in this series can perform harmonic analysis continuously, quickly and accurately.

2.2 Testing of variable frequency power supply and inverter power supply

Figure 1 Schematic diagram of power supply test system

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

2.3 Testing of AC regulated power supply

There are many types of AC regulated power supplies, which are widely used, and their voltage stabilization principles are also different. There are parameter adjustment type, auto-coupling adjustment type, high-power compensation type, switch type, etc. However, their input voltage range, input side current distortion, source power factor, output waveform, load adaptability, voltage stabilization accuracy, overall 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, has a harmonic analysis function, can directly display the measurement results from the panel, and can also print or communicate the measurement data and waveform. It is an ideal test tool for AC power.

2.4 Switching power supply test

The rapid development of power electronics technology has promoted the rapid development of switching power supplies, especially high-frequency switching power supplies. Switching power supplies have been widely used in electric vehicles and variable frequency drives. Power factor and overall efficiency are important parameters that must be examined for switching power supplies. Using power factor correction technology to improve the input power factor of the switching power supply 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 harmonic distortion measurement function, which is a good helper to help improve the power factor of switching power supplies.

2.5 Testing of electronic transformers

Electronic transformers are common power devices because they are simple, practical and have 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 mass production lines to eliminate unqualified products. The transformer-specific tester in the Yuanfang PF series digital power meter is developed based on this demand. The transformer-specific tester can simultaneously test the primary and secondary electrical parameters of the electronic transformer, automatically switch the no-load and load electrical parameters of the test transformer, and automatically determine whether the transformer is qualified based on the electrical parameters set by the user, and use sound and light alarms. After setting the measurement conditions for this special tester, you only need to press a test button to complete all the testing and judgment work of an electronic transformer. It is a powerful assistant for mass production of electronic transformers.

3PF Series Digital Power Meter Measurement Principle

The PF series digital power meters of Yuanfang are diverse in variety and complete in functions. They mainly include single-phase series, three-phase series and special series. The following uses a single-phase digital power meter as an example to explain the typical measurement principle of the PF series digital power meter of Yuanfang. [page]

3.1 Schematic diagram

The instrument is mainly composed of input part, single-chip computer, display and interface part, as shown in Figure 2. In the voltage input circuit, the input voltage is program-controlled amplified after the voltage divider, sent to the A/D converter after the sample and hold, and 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-voltage converter, and then program-controlled amplified, sent to the A/D converter after the sample and hold, and the conversion result is placed in the voltage buffer. The single-chip computer reads the waveform data from the buffer and processes the data. 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 the host computer with rich data, such as sampled waveform data, various measurement and operation 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 measurement waveforms, harmonic spectra, etc., or processing them together with data provided by other test equipment.

Figure 2 Schematic diagram of digital power meter

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 a measurement report

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

INPUTWAVEFORM (input waveform)

Display value: Ui=225.5VIi=0.752APi=0.131kW

PFi=0.777Fi=50.05Hz

Uthd=4.220％Ithd=64.11％

OUTPUTWAVEFORM (output waveform) [page]

Figure 3 Example of PF9832 AC Power Analyzer Test Report

Display value: Uo=220.8VIo=0.187APo=0.041kW

PFo=0.999Fo=50.01Hz

Uthd=0.887%Ithd=2.888%EFF=0.313

4 Conclusion

The PF series digital power meter from Yuanfang offers users more choices, ranging 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 multifunctional models. The successful application of the PF series digital power meter in multiple systems also proves that it can meet the needs of scientific research, production, and quality inspection of various power equipment, and is the core tool of the power test system.