UPS Power Evaluation (1)

The purpose of testing the UPS power supply is to determine whether the practical technical indicators of UPS can meet the requirements. UPS testing generally includes both steady-state testing and dynamic testing. The steady-state test is performed under no-load, 50% rated load, and 100% rated load conditions, test the phase voltage, line voltage, no-load loss, power factor, efficiency, output voltage waveform, distortion and output voltage frequency at the input and output ends. Generally, when the load is changed from 0 to 100% and from 100% to 0), the UPS output voltage waveform changes, to test the dynamic characteristics of UPS and the Energy Feedback path.

I. steady state test

The so-called steady-state test refers to the test when the device enters the "normal system" state. Generally, waveforms, frequencies, and voltages can be measured.

Waveform

It is generally used to observe whether the waveform is normal when there is no load or full load. A distortion measuring instrument is used to measure the distortion of the output voltage waveform. Under normal working conditions, the relative content of the total harmonic of the output voltage should be measured by a Distortion Measuring Instrument under resistance load, which should comply with the requirements of the product, generally less than 5%.

Frequency

Generally, the frequency of the output voltage can be observed using an oscilloscope and measured using a power disturbance analyzer. At present, the output voltage frequency of the UPS can generally meet the requirements. However, when the UPS frequency circuit and the local oscillator are not accurate enough, the frequency of UPS output voltage may also change when the mains frequency is unstable. Generally, the accuracy of UPS output frequency is equal to or greater than 0.2% when it is synchronized with the mains supply.

Output Voltage

You can use the following methods to test and determine the UPS output voltage:

A. When the input voltage is 90% of the rated voltage, the output load is 100%, the input voltage is 110% of the rated voltage, and the output load is 0, the output voltage shall be kept within the range of plus or minus 3% of the rated value.

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

C. When the input DC voltage of the UPS inverter changes by plus or minus 15% and the output load changes from 0 to 100%, the output voltage value should be within the range of the rated voltage value plus or minus 3%. This indicator appears to be repeated with the preceding indicator, but in fact it is more demanding than the previous indicator. This is because when the input signal of the control system changes in a wide range, it shows obvious non-linear characteristics. To make the output voltage not exceed the permitted range, the circuit requirements are higher.

Efficiency

The UPS efficiency can be obtained by measuring the output power and input power of the UPS. The UPS efficiency mainly depends on the inverter design. Most UPS instances have high efficiency only when the load is between 50% and 100%. When the load is lower than 50%, the efficiency decreases sharply. The efficiency indicators provided by the manufacturers are mostly rated DC voltage, efficiency under rated load conditions. It is best for users to select the relationship between efficiency and output power and the efficiency when the DC voltage changes plus or minus 15%.