In an online UPS, the batteries are always connected to the inverter, so it is not necessary to have a power transfer switch. When a loss of power occurs, the rectifier just drops out of the circuit and the batteries keep the flow of power steady and unchanged.

 When the power is restored, the rectifier resumes carrying most of the load and begins charging the batteries. However, the charging current may be limited to prevent the high-power rectifier from overheating the batteries and boiling off the electrolyte. The most beneficial advantage of an on-line UPS, in comparison with the other types of UPS, is its ability to provide an “electrical firewall” between the incoming utility power and sensitive electronic equipment.

The online UPS is ideal for environments where electrical isolation is necessary or for equipment that is very sensitive to power fluctuations. However, with the advances in technology, the online UPS unit was once only used for very large installations of 10 kW or more. Now they are available as a common consumer device, supplying 500 W or less.

The initial cost of the online UPS may be higher, but its total cost of ownership is generally lower due to longer battery life. The online UPS may be necessary when the power environment is “noisy”, when utility power sags, outages and other anomalies are frequent, when protection of sensitive IT equipment loads are required or when operation from an extended-run backup generator is necessary.

The basic technology of the online UPS is the same as in the standby or line-interactive UPS. However, it typically costs much more, due to it having a much greater current AC-to-DC battery-charger/rectifier, and with the rectifier and inverter designed to run continuously with improved cooling systems. It is called a double-conversion UPS due to the rectifier directly driving the inverter, even when powered from normal AC current. At UPS Battery Centre, our goal is not to only sell batteries, we want to inform and teach you about the amazing world of batteries, electricity and energy. Please check back for more interesting, helpful and informative articles about batteries and electricity.

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