Successful testing of the UPS system is a complicated and inherently unsafe operation—if you don’t do it properly. After 10 years of successful continuous service, the UPS systems in our data center also collapsed. While this incident has left us helpless for just a few minutes, the healing process has taken months.
In the post-mortem quest for a smoking shot, we pulled buckets of failed parts, like diodes, connectors, printed circuit boards, SCRs, spark plugs, and even logic power supply control. We never noticed the gun while there was a lot of smoke. In fact, our opinion shifted from dismay at the loss to be astounded that the box was able to function and produce energy at all. We’ve come to realize that simply because the UPS is up and running, it doesn’t mean it’s fully operational.
As a result, we re-engineered our research procedures to begin practical testing of our UPS equipment along with its related batteries. We agreed on a course of action focused primarily on traditional factory acceptance research—divided into three phases: physical preventive maintenance (PM), safety and calibration environments, and practical load testing (including battery discharge).
Let's take a closer look at each of these stages.
Physical PM: This involves infrared scanning until the device is shut down. Bad power connections can result in a higher temperature state than the surrounding temperature. This state occurs on an infrared scan. By buying a reasonably inexpensive camera, you will conduct an unbiased search if the package is opened or a particular inspection is warranted.
It’s essential that you check all the connections and tighten them. The minor ground will cause transients on the logical power supply that will influence the control of the device. Use an infrared detector, look for loose power supply links, diodes, capacitors, inverter gates, and drive boards. Inspect the capacitor cans for swelling, leakage, or pop-up pain.
Protection and calibration settings: Test the safety settings and calibrate the UPS device. By simulating an alarming situation, the technician can check that both alarms and security settings are in place. If UPS system metering is out of calibration, its function can be impaired. For e.g., a meter that measures DC bus voltage affects DC overvoltage or under voltage warning and security. If the UPS is moved to battery service, the subsequent discharge of the battery can continue for too long. As the battery voltage decreases, the current needs to rise in order to continue supporting the same capacity. If the current is so strong, the temperature in the control circuit rises to the level of destruction.
Functional load checks: Functional load checking can be broken down into six different operations, including steady-state load testing, harmonic analysis, filter integrity, transient response test, module fault test, and battery rundown. For systems with several components, the Module Defect Test and Restore should also be done.
Steady-state load test
Under a steady-state measure, all input and output conditions should be tested at 0 percent, 50 percent and 100 percent load. Check the following parameters: input and output voltage, input and output current, output frequency, input current equilibrium, and output voltage control. The study will show whether input currents fit all phases of the module and decide whether all modules share loads equally. Since power is equal to voltage times current, a degraded voltage from a single module or phase means that other modules or phases must generate more current to withstand a voltage drop.
During the steady-state load test, you can track the input and output of the UPS for harmonic content. By analyzing the harmonic material at 0 percent, 50 percent and 100 percent load, you will assess the efficacy of the input and output filters. It is important to remember that most manufactures build UPS filtering systems for optimum performance at full load. As a consequence, the harmonic distortion is highest when the device is least loaded and smoothed out as the load increases. On the grounds that distortion is persistent across phases and modules, there is no cause for concern.
Total harmonic distortion (THD) is simply a measure of the divergence from the ideal sinusoidal wave. A high THD load takes more energy to support than a low THD unit. Waste energy dissipates like heat. Although unreliable, UPS working with high THD at low load is not at risk of damaging conduction components. UPS running with high THD at high load is highly taxed since the device generates electricity to support the load along with extra heating. The harmonics can be measured at the following points: input voltage, output voltage, input current and output current.
There are three common filter components for most UPS systems: input, rectifier and output. Filters typically use resistors, inductors, and capacitors to eliminate unwanted waveform elements. Thermal scans typically pick up signs of an inductor malfunction. Capacitors are more vulnerable to tension loss. Based on the capacitor, they are susceptible to accelerated expansion and depletion of acid electrolyte when overstressed or dried over time.
Virtually hundreds of capacitors are wired in series and placed in banks in large 3-phase UPS networks. Identifying a single failed capacitor can be time-consuming and complicated. Running a relative step current balance is an easy way to verify the integrity of the filter.
You may do a quantitative assessment by testing the current step through each leg of the filter. A marked difference in the phase currents produced by the filter assembly suggests that one or more capacitors have degraded.
Battery rundown test
Your last test should be a rundown of the battery. Sometimes the battery system can be prone to faults that are undetected. The most meaningful test of the battery is to track temperature, voltage and current under loading conditions. Dissimilar cell-to-cell or string-to-string voltages are a direct indicator of the deterioration of the battery. The load test would depend on the type of battery attached to the UPS. Wet-cell batteries are more durable and able to run a year between full battery rundown checks. The valve-controlled batteries are quickly overstressed by a full battery rundown, so you can monitor them more frequently.
You can constantly check the battery cell voltages manually or with a cell monitor when performing a discharge test. If the battery string is no longer capable of supplying the intended discharge time (e.g. 15 min) or 80 per cent of the rated power, so it is time to consider a complete battery replacement.
Successful UPS monitoring is a dynamic and potentially unsafe process if you do not perform it correctly. Hiring a test-engineering community with a good UPS servicing and research background is typically best. While rigorous testing of the UPS machine can be expensive and time-consuming, costs associated with an unanticipated loss of business and production greatly outweigh those incurred as a result of testing. Need more technical support from experts or want to buy the best one for your home, office or data center then contact MultilinkEng Pakistan.