(l) cleaning and inspection. UPS in normal use, the host of the maintenance work is very little, mainly dust and dust removal on a regular basis. Especially in dry climatic areas, more dust in the air, the machine's wind machine will bring the dust deposited in the machine, when the air is humid will cause the host control disorders, resulting in the host malfunction, and inaccurate alarms, a large amount of dust will also cause the device is not good heat dissipation. Generally every quarter should be thoroughly cleaned. Secondly, when the dust is removed, check the connections and plugs for loose and poor contact. Measure the voltage of the battery pack, replace the unqualified battery, check the fan operation and testing and adjusting the system parameters of the UPS. To often wipe the battery with a soft rag to keep the battery surface clean.
(2) Replenishment and float charging. Regular maintenance can extend the service life of the UPS, for a long time in only charging and not discharging state of the UPS (utility is very stable), the battery in the UPS will not have the opportunity to work, the battery may be damaged due to prolonged float charging. The electrical energy in the battery may be depleted or nearly depleted for some reason. In order to compensate for the battery energy and improve battery life, should be every two or three months to artificially interrupt the utility power, let the battery discharge for a period of time to activate the battery. At the same time, UPS should be timely, longer continuous charging (usually not less than 48h, with or without load), in order to avoid failure caused by battery failure. On the contrary, if the utility frequent interruptions or long-term low voltage state, with the growth of UPS use time, there is always part of the battery charging and discharging characteristics will gradually become worse, that is, burst into the deterioration of the state. This trend is especially obvious in the backup UPS and some online UPS. Mainly because in this type of UPS used in the battery charging circuit is a constant voltage cut-off charging circuit, coupled with the UPS in the battery in a long-term state of discharge. After a period of operation, often found that the internal resistance of the battery increases, the terminal voltage of individual batteries in the battery pack decreased significantly, these are the normal loss of battery. Need to use the high voltage late at night to charge the battery pack (generally 10-12h), to prevent its deep discharge. For improper use and damage to the battery, normal charging generally can not make it recover, you can use a special constant current charger, the internal resistance has been very high battery activation, in order to revive it.
The UPS is not used for a long time to carry out artificial forced work at regular intervals, so that not only can activate the battery, but also to check whether the UPS is in a normal state, and can make the operator familiar with the use of UPS power supply system.
UPS in use, once a month to check the float voltage, a single battery float charge voltage is lower than 2.2OV (relative to 2V battery), then the whole group of batteries should be equalized charging. If the user configures the long-delay battery pack by himself, the external charger should have the function of constant voltage and constant current at the same time, and the charger with only constant voltage function should not be used, so as not to affect the service life of the battery.
2. UPS system testing
The purpose of testing the UPS is to identify the actual technical indicators of the UPS to meet the requirements of the use of UPS testing generally includes steady-state testing and dynamic testing of two types. Steady state test is in no load, 50% rated load and 100% rated load conditions, test input, output phase voltage, line voltage, no-load loss, power factor, efficiency, output voltage waveform, distortion and output voltage frequency. Dynamic testing is generally a sudden change in the load (generally choose the load from 0-100% and from l00%-0), test the UPS output voltage waveform changes to check the dynamic characteristics of the UPS and feedback loop.
(1) Steady state test. In the UPS into the "system normal" state of the waveform, frequency, voltage and efficiency of the test method is as follows.
1)Waveform test. Generally in the no-load and full-load state, observe the waveform is normal, with the distortion meter to measure the distortion of the output voltage waveform. Under normal operating conditions, connected to the resistive load, with a distortion meter to measure the total harmonic relative content of the output voltage, should meet the requirements of the product regulations, generally less than 5%.
2) Frequency detection. Generally available oscilloscope to observe the frequency of the output voltage and "power disturbance analyzer" for measurement. When the UPS frequency circuit of the oscillator is not accurate enough, there may be in the utility frequency instability, UPS output voltage frequency also follow the changes. UPS output frequency accuracy is generally synchronized with the utility, can reach ± 0.2%.
3) output voltage. UPS output voltage can be tested 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 ± 3% of the rated value.
b)When the input voltage is 90% or 110% of the rated voltage and one phase of the output voltage is no load and the other two phases are 100% loaded, its output voltage shall be kept within ±3% of the rated value and its phase difference shall be kept within 4°.
C) When the input DC voltage of the UPS inverter varies by ±15%, and the output load varies from 0-100%, the output voltage value should be maintained within ±3% of the rated voltage value. This indicator superficially duplicates the previously described indicators, but in fact it is more demanding than the previous indicators. This is because the input signal of the control system in a wide range of changes in the input signal, showing obvious nonlinear characteristics, to make the output voltage does not exceed the permissible range, the circuit requirements are higher.
d) efficiency. the efficiency of the UPS can be obtained by measuring the output power of the UPS and input power. the efficiency of the UPS is mainly determined by the design of the inverter. Most of the UPS only in 50% -100% load has a relatively high efficiency, when less than 50% load, its efficiency drops sharply, manufacturers provide efficiency indicators are mostly in the rated DC voltage, rated load conditions of efficiency.
(2) dynamic test.
1) sudden increase or decrease in load test. First use the "power disturbance analyzer" to measure the no-load, steady state phase voltage and frequency, and then suddenly add load from 0 to 100% or sudden load reduction from 100% to 0, if the UPS output transient voltage in a 8% to 10%, and in 2Oms return to steady state, the UPS the index is qualified; if the UPS output transient voltage exceeds this range, the UPS output voltage will be reduced to 10%. If the UPS output transient voltage exceeds this range, it will produce a large inrush current, both on the load and on the UPS itself is extremely unfavorable.
2) conversion characteristics test. This main test from the inverter power supply to the utility power supply or from the utility power supply to the inverter power conversion characteristics. The test requires an oscilloscope with storage function and a regulator that can simulate the change of utility power.
3) overload test. Overload test is an important measure of UPS indicators, overload test is mainly to test the UPS machine overload capacity, to ensure that even if the operation of the phenomenon of overload, the UPS can maintain a certain period of time without damaging the equipment. Overload test must be tested according to the equipment indicators, and to be carried out at room temperature within 25 ℃.
4) input voltage overvoltage, undervoltage protection test. According to the equipment indicators input voltage allowable changes in the range of tests, the general UPS allows input voltage changes of 10%, when the input voltage exceeds this range should be alarmed and converted to battery power supply, rectifier automatically shut down, when the input voltage is restored to the rated allowable range, the equipment should automatically resume operation, that is, automatically switch to run from the utility. In the process of automatic battery casting and lifting, the UPS output power waveform should be unchanged.