The best uninterruptible power supply system for small businesses and internet servers is a line interactive UPS system. This UPS system has some features not normally found on a standby UPS system.
The inverter of a line interactive UPS system is always connected to the main source of power. Power basically flows through the inverter and into the equipment that requires power. Due to this, the response time to a power failure is faster compared to a standby UPS system. The design also provides added protection to the equipment connected to the system since the inverter may come with additional features to protect against unexpected power spikes.
On the other hand, the battery is connected to the inverter and is constantly charged while the main source of power still provides power into the system. When the main power source goes out, the transfer switch opens up to allow the battery to provide power to the equipment connected to the system.
A line interactive UPS system also features a transformer that automatically adjusts the voltage when the source of power changes from utility power to battery. This is essential since it may be necessary to increase the voltage of the power provided by the battery. It is also important to adjust or regulate the voltage in low voltage situations. In these situations, the system may continuously transfer the source of power from the power line to the battery and vice-versa. When the battery is used frequently, it will result in its premature failure.
The main benefits of using a line interactive UPS system are its efficiency and reliability. The system is also small and cheaper compared to a double conversion online UPS system. Despite these advantages, it still takes some time for a line interactive UPS system to transfer its source of power to the battery when power coming from the utility line goes out.
References:
http://www.pcguide.com/ref/power/ext/ups/typesLineInt-c.html
http://www.apc.com/us/en/faqs/FA157448/
http://qpsolutions.net/2015/06/line-interactive-vs-double-conversion-ups-which-ones-best/
http://www.gocsc.com/uploads/white_papers/CDA24729556646388C183D4320810EF7.pdf