Uninterruptible power supplies are meant to serve as an emergency or backup source in case of power failure. One of the defining characteristics of UPS systems that set them apart from generators is that the flow of electricity is not interrupted at all during the switchover from the electrical grid to the UPS or vice-versa. This is why it is called "uninterruptible".
All it needs is a storage battery and an inverter to convert DC to AC. The battery charges itself when the grid is functioning normally. If the grid voltage falls below a predefined level, the backup kicks in and starts powering the connected devices instead.
UPS systems come in three types that can be classified as SPS or Standby, Double-Conversion or Online, and Line Interactive. The difference between these types is mainly regarding the switchover from the grid to backup. The standby type is the simplest option with a mechanical switch that shifts the circuit from the external AC grid outlet to the battery.
Note that this changeover is done so fast (max 25 milliseconds) that connected equipment like a computer won't be affected or get switched off. But the double-conversion UPS will eliminate even this tiny powerless state. In this case, all the components are in the same circuit.
A rectifier converts the AC grid to DC and sends it to the battery, which is connected to the inverter. The inverter converts it back to AC and powers connected devices. In case the AC grid fails, the battery won't get any input but it still continues sending its output to the inverter.
Unlike generators, typical uninterruptible power supplies are unable to keep computers and printers on for longer periods. An ordinary SPS usually has a battery usage time of around 15-20 minutes. But they do provide the opportunity to finish or save on-going activities and shut down computers in an orderly manner.
All it needs is a storage battery and an inverter to convert DC to AC. The battery charges itself when the grid is functioning normally. If the grid voltage falls below a predefined level, the backup kicks in and starts powering the connected devices instead.
UPS systems come in three types that can be classified as SPS or Standby, Double-Conversion or Online, and Line Interactive. The difference between these types is mainly regarding the switchover from the grid to backup. The standby type is the simplest option with a mechanical switch that shifts the circuit from the external AC grid outlet to the battery.
Note that this changeover is done so fast (max 25 milliseconds) that connected equipment like a computer won't be affected or get switched off. But the double-conversion UPS will eliminate even this tiny powerless state. In this case, all the components are in the same circuit.
A rectifier converts the AC grid to DC and sends it to the battery, which is connected to the inverter. The inverter converts it back to AC and powers connected devices. In case the AC grid fails, the battery won't get any input but it still continues sending its output to the inverter.
Unlike generators, typical uninterruptible power supplies are unable to keep computers and printers on for longer periods. An ordinary SPS usually has a battery usage time of around 15-20 minutes. But they do provide the opportunity to finish or save on-going activities and shut down computers in an orderly manner.
About the Author:
At the UPS Company we are providers of power protection and service solutions including UPS systems, standby Diesel Generators, power stabilisers, inverters, DC power supply systems, software and other accessories.
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