The purpose of testing the UPS power supply is mainly to determine whether the actual technical specifications of the UPS can meet the requirements for use. UPS 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.
First, 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.
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%.
frequency
Generally, the oscilloscope can be used to observe the frequency of the output voltage and measure with the “Power Disturbance Analyzerâ€. At present, the output voltage of the UPS can generally meet the requirements. However, when the frequency circuit of the UPS 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.
The 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 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.
effectiveness
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%.
Second, dynamic testing
1, sudden or sudden load test
First use the "Power Disturbance Analyzer" to measure the phase voltage and frequency at no-load, steady state, then suddenly increase the load from 0 to 100% or the sudden load from 100% to 0, if the UPS output transient voltage is at -8% Between 10% and return to steady state within 20ms, the UPS is qualified; if the UPS output transient voltage exceeds this range, a large inrush current will be generated, regardless of the load or the UPS. It is extremely unfavorable in itself, so this kind of UPS should not be used.
2, conversion characteristics test
This main test is the conversion characteristic when the inverter is powered to convert to the mains supply or when the mains supply is converted to the inverter. The test requires a storage oscilloscope and a voltage regulator that simulates changes in mains.
Third, other routine testing
Overload test
Overload testing is extremely important to users and an important indicator of UPS power. The overload test is mainly to check the overload capacity of the UPS to ensure that the UPS can maintain a certain time without damaging the equipment even if there is an overload phenomenon during operation. Overload equipment must be tested in accordance with equipment specifications and at room temperature within 25oC.
Input voltage overvoltage, undervoltage protection test
According to the equipment index input voltage allows the variation range to be tested. Generally, the UPS allows the input voltage to change by 10%. When the input voltage exceeds this range, it should alarm and switch to battery power supply. The rectifier will automatically turn off when the input voltage returns to the rated allowable range. The equipment should be automatically resumed, that is, the battery is automatically released and turned into commercial power. During the automatic input and release of the battery, the UPS output power waveform should be unchanged.
Discharge test
The discharge test is mainly to check the performance of the battery. In the discharge test, the first is to record the discharge time; the second is to observe the output voltage waveform and the discharge protection value during discharge; the third is to check whether there is a "backward" battery, and the battery must be continuously charged for 24 hours before the discharge test. .
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