DISTINGUISHING BETWEEN ONLINE UPS AND OFFLINE UPS

Operating principle of UPS OFFLINE:
- When the grid power is stable, the load consumes power directly from the grid.
- At this point, the UPS only uses a charger to automatically charge the battery.
- When the grid voltage is not stable (too high, too low) or there is a power outage, the circuit switches to using power supplied from the battery and the inverter..

Disadvantage: The switching time from a grid power failure until battery power supplies the load. The switch that disconnects power from the grid to switch over to battery power must ensure that power from the inverter is only supplied once it is completely disconnected from the grid (in practice, these UPS units have up to two such "switches" of this kind controlled simultaneously - in engineering these are usually called "relays"), because otherwise the current supplied by the battery would also have to feed the local grid - and, like a generator, the system would be damaged from overload.

UPS ONLINE:
At this point, the grid power does not supply power directly to the devices; instead, it is converted into DC current corresponding to the battery voltage. Here, the circuit shows the power supply from the battery and from the grid power itself to the inverter, which converts it into an output voltage suitable for the equipment used.

Thus, it can be seen that in the event of any power grid fault, an online UPS can supply power to the connected equipment without any delay. This makes the equipment very safe and stable to use. An online UPS always keeps the output voltage stable because, according to the circuit, the input voltage is converted down to the battery voltage level and acts like a battery of virtually unlimited capacity (as long as there is no grid fault), with the inverter circuit acting as a voltage stabilizer. Therefore, only online UPS types provide truly thorough voltage stabilization.

Read more Guide to Choosing a UPS