4.6Transformer
The UPS’s transformer is an electrical component which “steps up” the output voltage of the inverter to the normal utility line voltage. In addition, it serves to isolate the UPS from equipment failures.
4.7 Monitoring and control electronics
This block is the “brain” of the UPS. The monitoring and control circuitry detects utility failures such as blackouts, sags and brownouts; synchronizes the inverter’s output frequency and phase to that of the utility; detects low battery voltage conditions; directs the load transfer switch; and governs all user controls, indicators and computer interface functions.
4.8Operationduringautilityfailure
In anticipation of a utility failure such as a blackout, sag or brownout, the UPS continu- ously monitors the utility voltage and readies the inverter for “synchronous” transfer. This means the inverter’s phase and frequency is adjusted to match the phase and frequency of the utility. If the utility voltage falls outside acceptable limits, the UPS rapidly transfers your equipment to power derived from the UPS’s battery via the inverter and transformer described earlier. This transfer typically takes place within 8 milliseconds. Once operating in this mode, the UPS will beep once every 5 seconds to alert the user that there is limited time available to save files and shut down the computer. If the utility power is not restored to normal, the UPS will eventually sound continuous beeps to alert you that less than two minutes remain before the UPS shuts down and ceases to power your equipment. This is called a low battery condition which means that the UPS’s usable battery capacity is nearly spent. The UPS will automatically shut down if the UPS is not turned off during the low battery alarm.
If the UPS detects the return of normal utility voltages at any time during operation using its alternate power source, the inverter voltage will be smoothly
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