October 27, 2021

How to easily perform steady state and dynamic testing of UPS power supplies

UPS power supply testing generally includes two types of steady state testing and dynamic testing. Steady-state test is to test the input and output phase voltage, line voltage, no-load loss, power factor, efficiency, output voltage waveform, distortion and output voltage under no-load, 50% rated load and 100% rated load conditions. The frequency and so on. Dynamic testing generally tests changes in the UPS output voltage waveform when the load is abrupt (generally selected from 0-100% and 100%-0) to verify the dynamic characteristics of the UPS and the energy feedback path.

1 waveform

Generally, when the waveform is in the no-load and full-load state, whether the waveform is normal or not is measured, and the distortion of the output voltage waveform is measured by the distortion measuring instrument. Under normal working conditions, connect the resistance load, and measure the relative content of the total harmonic of the output voltage with the distortion measuring instrument, which should meet the requirements of the product, generally less than 5%.

2 steady state test

The so-called steady state test refers to the test when the device enters the "system normal" state, and generally can measure the waveform, frequency and voltage. The frequency can generally be measured by the oscilloscope to observe the frequency of the output voltage and using the "Power Disturbance Analyzer". At present, the output voltage frequency of the ups uninterruptible power supply generally meets the requirements. However, when the frequency circuit of the UPS power supply and the local oscillator are not accurate enough, it is also possible that the frequency of the UPS output voltage also changes when the mains frequency is unstable. The accuracy of the UPS output frequency is generally 0.2% plus or minus when synchronized with the mains.

3 efficiency

The efficiency of the UPS can be obtained by measuring the output power of the UPS and the input power. The efficiency of the UPS is mainly determined by the design of the inverter. Most UPSs have higher efficiency only when they are 50%-100% load. When the load is lower than 50%, the efficiency is drastically reduced. The efficiency indicators provided by the manufacturers are mostly under the rated DC voltage and rated load conditions. effectiveness. When selecting the user, it is best to choose the relationship between efficiency and output power and the efficiency when the DC voltage changes by 15%.


4 output voltage

The output voltage of the UPS can be tested and judged by the following methods:

A. When the input voltage is 90% of the rated voltage, and the output load is 100% or the input voltage is 110% of the rated voltage. When the output load is 0, the output voltage should be within 3% of the rated value. .

B. When the input voltage is 90% or 110% of the rated voltage, one phase of the output voltage is no-load, and when the other two phases are 100% load, the output voltage should be kept within the range of plus or minus 3% of the rated value. The phase difference should be kept within 4 degrees.

C. When the input DC voltage of the UPS power inverter changes by plus or minus 15% and the output load changes from 0-100%, the output voltage value should be within 3% of the rated voltage value. This indicator is superficially duplicated with the previously stated indicators, but in fact it is more demanding than the previous indicators. This is because when the input signal of the control system changes over a wide range, it exhibits obvious nonlinear characteristics. To make the output voltage not exceed the allowable range, the circuit requirements are higher.

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