UPS power output load short circuit problem
If the UPS output load is short-circuited by more than 90%, it will cause the UPS system to output power failure or flash failure, which will lead to the paralysis of the power supply of the connected important equipment. When the UPS output load is short-circuited, no matter the stand-alone, master-slave, parallel, or double bus system can not guarantee the uninterrupted power supply of the load. Take the safest and most reliable UPS parallel dual-bus redundant power supply system as an example. 4 UPSs each 1+1 with parallel cabinets and *** dual bus power supply, UPS1-1 and UPS1-2 pass through the parallel cabinets and parallel cabinets. The machine constitutes the system Ⅰ, UPS2-1 and UPS2-2 form the system Ⅱ through the parallel cabinet and machine. Under normal circumstances, System I and System II have their own loads. System I is loaded with UPS1 output cabinet and static transfer switch STS1, and System II is loaded with UPS2 output cabinet and static transfer switch STS2. When any equipment on the power supply bus of System I fails, its load can be switched by the static transfer switch to provide power to another system. In order to ensure that the two systems can be at the same frequency and phase, the load bus can also be synchronized with the controller to ensure that the power supply is continuous in waveform and phase during switching. For most faults, this system has no problem, but it still cannot solve the problem of output load short-circuit. This is because a short circuit is equivalent to an overload. When switching to System II, System II will also be overloaded and shut down, causing the load to lose power.
The possibility of output short circuit in actual work is very high. Nowadays, the UPS systems in the core computer rooms of many operators are in parallel mode. Two UPSs are connected in parallel through a UPS power distribution cabinet/distribution box to supply power to all the data, monitoring, and billing equipment in the computer room. From the main UPS power distribution cabinet to each load, it may also pass through several power distribution cabinets, distribution boxes, and sockets. A short-circuit failure in any one of the links may cause the whole system to power off. In addition, the maintenance interface between different operators, different cities and professions is not the same. Some are that all power supplies are maintained by the power professional; some are the UPS main power distribution cabinets are maintained by other professionals, and the UPS main power distribution cabinets are maintained by the power professional maintenance. Other majors may be lacking in power skills, there are many uncertainties, and there may be short circuits. UPSs give priority to protecting their own equipment. Different manufacturers have different design concepts. When the output is short-circuited, some UPSs do not switch to bypass, and directly turn off the inverter. power failure. The author has encountered two 30kVA UPS machines. During installation and commissioning, due to the careless operation of the construction personnel, the UPS output power distribution cabinet busbar of the equipment side was short-circuited, and the two UPS inverters stopped working and did not switch to the bypass. Disconnect and turn off the mains input switch, and restart it to return to normal.
How to avoid UPS output load short circuit leading to system downtime? At present, equipment manufacturers have made most important network communication equipment into equipment with dual power input characteristics. There are two AC power ports, which can be connected to two AC power sources, which are converted into DC power through two AC/DC conversion modules internally, which are connected in parallel to supply power to the equipment. However, in actual work, generally only one AC power interface is used, or at most one wire is used and connected to the first power interface.
This only solves the redundant protection of the AC/DC conversion module, and it is the best way to accidentally disconnect the power cord or output short-circuit. In order to maximize the technical potential of dual power input devices, avoid UPS output short-circuits causing system downtime, and ensure the safety of power supply for important equipment, the best solution is to use two sets of dual-bus parallel systems to provide important equipment. The 2 power ports are powered. This not only solves the problem of cable redundancy, but also solves the problem of output short circuit. Although the construction cost is higher, the safety is greatly improved, and it is worthwhile for important equipment.