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Wednesday, October 17, 2007

Kleynhans identifies various types of UPS

The regional director for Africa at APC-MGE, Mr. Carl Kleynhans, has identified the need to know various types of uninterruptible power supplies (UPS’).

This, he said, would enable consumers to take adequate decisions and make good choice.

He noted that with several types of UPS in the market nowadays, it has become essential to understand the various characteristics of UPS, their strengths and weaknesses.

“In order for a company to make an educated decision as to the appropriate UPS topology for a given need,” he said.

Mr. Kleynhans enlightened that with varied types of UPSes and their attributes often cause confusion within the data centre industry specifically.

He cited an example, that it is widely believed that there are only two types of UPS systems, namely Standby UPS and Online UPS, stressing that these two commonly used terms do not correctly describe many of the UPS systems available.

“A variety of design approaches are used to implement UPS systems, each with distinct performance characteristics. The most common design approaches are Standby, Line Interactive, Standby on-line hybrid, Standby-Ferro, Double Conversion On-Line, and Delta Conversion On-Line.

Explaining further, he said, that Standby UPS is the most common type used for Personal Computers (PCs). The transfer switch is set to choose the filtered AC input as the primary power source and switches to the battery/ inverter as the backup source should the primary source fail.

“When that happens, the transfer switch must operate to switch the load over to the battery/ inverter backup power source, as such the inverter only starts when the power fails, hence the name Standby,” he said.

The Line Interactive UPS, he said, is the most common design used for small business, web and departmental servers, usually designed with the battery-to-AC power converter (inverter) always connected to the output of the UPS.

“Operating the inverter in reverse during times when the input AC power is normal provides battery charging,” Mr. Kleynhans said.

On the Standby On-Line hybrid, he said, its the topology used for most UPS under 10kVA, which are labelled “on-line” and affords the converter from the battery to switch on when an AC power failure is detected, just like in a standby UPS, even as the battery charger is small, similar to that in a standby type UPS and does not exhibit no transfer time during an AC power failure.

Equally, he informed that the Standby-Ferro UPS was once the dominant form of UPS in the 3 - 15kVA range and designed dependent on a special transformer that has three windings (power connections).

“The primary power path is from AC input, through a transfer switch, through the transformer and to the output. In the case of a power failure, the transfer switch is opened, and the inverter picks up the output load,” he pointed out among others.

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