美国维缔艾默生UPS电源ITA 10K00ALA102C00接入各类NMS网管系统
随着计算机应用系统对电源的要求越来越高UPS日益受到重视，并逐渐发展成为一种具有稳压、稳频、滤波、抗电磁和射频干扰、防电压冲浪等功能的电力保护系统。尤其是在电网的线路及供电质量不太高、抗干扰的技术落后，计算机系统对电源的要求又比较高的情况下，UPS的作用就显得更加明显。 [4]
UPS的保护作用表现在对市电电源进行稳压，UPS的输入电压范围比较宽，一般情况是从170V到250V，而输出电源的质量是相当高的，后备式的UPS输出电压在5%~8%，输出频率稳定在1Hz；如图1，在线式UPS输出电压稳定在3%以内，输出频率稳定在0.5Hz。在市电正常时，UPS电源相当于交流市电稳压器；市电对蓄电池进行充电，此时也相当于充电器。在市电突然掉电的情况下，UPS自动切换到蓄电池供电，使计算机维持正常工作，保护软硬件不受损害。
The parallel connection of inverters between the mains and loadis simply used as a backup power source. This type of UPS powersupply, when the mains power is normal, the load is completely anddirectly supplied by the mains power, the inverter does not performany energy conversion, and the battery is powered by an independentcharger; When the mains power is abnormal, the load is completelypowered by the inverter. [5]
Passive backup UPS has the advantages of simple structure andthe lowest price, and is used in some non important loads, such ashome computers. But when the mains power is cut off, the relayswitches the inverter to the load, which takes a long time andusually takes a few milliseconds of interruption. Therefore,passive backup UPS power supply should not be used for slightlyimportant computer equipment. [5]