White Paper On Merits of a Standby UPS with Modified Sinewave Output

Of the three major UPS architectures (e.g. standby, ferroresonant on-line, and double-conversion
on-line), the standby UPS features the following advantages:

	Features	Benefits
1.	Extremely high power efficiency, Typically above 97%.	Lowest operating cost in terms of electric use – only 1/10 of double-conversion on-line UPS.
2.	Air exhaust fan is normally off since very little heat is generated.	Quiet operation. Does not add to air conditioning loads.
3.	The inverter circuit is normally off.	Very quiet operation and the highest MTBF (mean-time-between failure) due to the lowest voltage, current and temperature of its internal parts.
4.	Cooler internal operating temperature.	Battery lifetime is approximately twice that of an on-line type UPS.
5.	Output waveform is normally a sinewave. The inverter waveform is a modified square-wave, generated only during power outages.	The pulse-width-modified and optimized peak-voltage modified square waveform is actually more beneficial for switchmode power supplies.
6.	Simplest and most economical UPS design.	Simple design with the lowest parts count. Means lowest purchase price and maintenance costs. Repair procedures are quick and easy.
7.	The switchover time of some high-quality standby UPS is less than 1ms.	The ride-through of typical switchmode power supplies is 10 to 20ms. A fast 1ms switchover time guarantees glitch-free transfers.

The above mentioned merits of a standby UPS with modified square-wave inverter output are the reasons for the popularity of the standby architecture in UPS sized under 1KVA. In fact, the vast majority (over 80%) of UPS under 1KVA being used today are of the standby type with millions installed in the USA alone.