Introduction to UPS power supply evaluation methods

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

1 Waveform

Generally, the waveform is observed to be normal in no-load and full-load states, and the distortion of the output voltage waveform is measured with a distortion meter. Under normal working conditions, a resistive load is connected, and the relative content of the total harmonics of the output voltage is measured with a distortion meter. It 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 equipment enters the "system normal" state, which can generally measure waveform, frequency and voltage.

Generally, the frequency of the output voltage can be observed with an oscilloscope and measured with a "power disturbance analyzer". At present, the output voltage frequency of UPS uninterruptible power supplies can generally meet 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 will change when the mains frequency is unstable. The accuracy of the UPS output frequency can generally reach plus or minus 0.2% when synchronized with the mains.

3. Efficiency

The efficiency of UPS can be obtained by measuring the output power and input power of UPS. The efficiency of UPS is mainly determined by the design of the inverter. Most UPS have relatively high efficiency only when the load is 50%-100%. When the load is less than 50%, the efficiency drops sharply. The efficiency indicators provided by the manufacturer are also mostly the efficiency under the conditions of rated DC voltage and rated load. When users select the model, it is best to choose the relationship curve between efficiency and output power and the efficiency when the DC voltage changes by plus or minus 15%.

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

1 Waveform

Generally, the waveform is observed to be normal in no-load and full-load states, and the distortion of the output voltage waveform is measured with a distortion meter. Under normal working conditions, a resistive load is connected, and the relative content of the total harmonics of the output voltage is measured with a distortion meter. It 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 equipment enters the "system normal" state, which can generally measure waveform, frequency and voltage.

Generally, the frequency of the output voltage can be observed with an oscilloscope and measured with a "power disturbance analyzer". At present, the output voltage frequency of UPS uninterruptible power supplies can generally meet 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 will change when the mains frequency is unstable. The accuracy of the UPS output frequency can generally reach plus or minus 0.2% when synchronized with the mains.

3. Efficiency

The efficiency of UPS can be obtained by measuring the output power and input power of UPS. The efficiency of UPS is mainly determined by the design of the inverter. Most UPS have relatively high efficiency only when the load is 50%-100%. When the load is less than 50%, the efficiency drops sharply. The efficiency indicators provided by the manufacturer are also mostly the efficiency under the conditions of rated DC voltage and rated load. When users select the model, it is best to choose the relationship curve between efficiency and output power and the efficiency when the DC voltage changes by plus or minus 15%.

4 Output voltage

The output voltage of the UPS can be tested and determined 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 and the output load is 0, the output voltage should be maintained within the range of plus or minus 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 the other two phases are 100% loaded, the output voltage should be kept within the range of plus or minus 3% of the rated value, and 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 by 0-100%, its output voltage value should be kept within the range of plus or minus 3% of the rated voltage value. This indicator is superficially repeated with the previous one, but in fact it has higher requirements than the previous one. This is because when the input signal of the control system changes in a large range, it shows obvious nonlinear characteristics. In order to keep the output voltage within the allowable range, the circuit requirements are higher.