For critical load, we need to ensure continuous and safe power. Pure power is equally important as an interrupted power supply. Thus, we need a device that provides both. UPS system not only offers battery back but also voltage fluctuation-free supply. Depending on the type of load, we need to choose a single or three-phase uninterruptible power supply.
There are mainly three types of UPS power systems. The offline unit only offers backup but with power interruption. A line interactive model offers backup with interruption with it provides a regulated power supply. An online Uninterrupted power system also offers backup, voltage regulator, and frequency regulation.
An online UPS system is a double-conversion device. It consists of rectifier, inverter, and batteries. A rectifier is connected to raw input power. It transforms AC power into DC power. This DC supply act as input for the inverter, and at the same time, it charges batteries continuously. An IGBT bridge inverter converts DC input to Alternating current.
The inverter can generate desired contact voltage and frequency with the help of the Pulse Width Modulation Technique (PWM). In the event of input power failure, the inverter takes power from the battery source. And this transition is without any delay since the inverter is always on. Since the inverter remains in the power line in all modes, it is called an Online UPS system.
Lead acid SMF or Nickel Cadmium batteries are generally used as a backup power supply with UPSs. The required battery backup time depends on the input power condition and criticality of the load. The cost of the UPS system is directly proportional to the battery backup time. Thus, we must choose it wisely to avoid financial losses and save floor space.