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The third type of uninterruptible power supply system is mainly designed for highly-sensitive equipment. The Double Conversion Online UPS System is the only UPS system with a zero transfer time: the power supply is not interrupted whenever an outage occurs. Due to this, the double conversion online UPS system is best for companies using equipment that is very important and sensitive or areas where the power supply is unpredictable.

It is called a double conversion since it has a second line where power can flow through. The second line is connected to the surge protector of the system, which basically protects it from any sudden increase in power.

The double conversion online UPS system is considered as the best UPS system in the market. Its main difference is that it uses the battery as its main source of power. Power coming from the utility line continuously charges the battery. When the power goes out, it is only the charger that stops functioning and the battery continues to provide power to the equipment until it runs out of charge.

But, there may be some rare instances when the inverter of the system fails. The inverter is the component that converts the direct current produced by the battery into alternating current, which is the type of current used by the equipment connected to the system. When this happens, there may be some delay in the transfer of source of power from the battery to the utility line. This is the only instance when the transfer of power from one source to another is not instantaneous, but the transfer time is typically counted in milliseconds (small fraction of a second).

Another concern raised about the double conversion online UPS system is the reduced efficiency and increase in heat. This happens since the power provided to the equipment passes through the battery and inverter. Continued use of these components can result to inefficiency and slight increase in temperature.

References:

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

http://www.eetimes.com/document.asp?doc_id=1272971

http://www.pcguide.com/ref/power/ext/ups/typesOnLine-c.html

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://www.upssystems.co.uk/standby-power-products/uninterruptible-power-supplies-ups/ups-technology/

http://qpsolutions.net/2015/06/line-interactive-vs-double-conversion-ups-which-ones-best/

http://www.gocsc.com/uploads/white_papers/CDA24729556646388C183D4320810EF7.pdf