NTT Data to Test DC-powered Data Center

Jun 25, 2008
Tetsuo Nozawa, Nikkei Electronics
NTT Data's concept of the data center using a DC power system: The DC-DC converters in the middle will eventually be "combined in the AC-DC converters located upstream or the DC-DC converter in the server machine," the company said.
NTT Data's concept of the data center using a DC power system: The DC-DC converters in the middle will eventually be "combined in the AC-DC converters located upstream or the DC-DC converter in the server machine," the company said.
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NTT Data Corp announced that it will start testing power-saving technologies such as DC power system in Oct 2008 at "Green Data Center," the company's data center equipped with many of such technologies.

After the testing, NTT Data will aim at launching a DC power service within fiscal 2009, the company said.

The DC power system is one of the technologies to minimize power loss by reducing the number of times of AC-DC/DC-AC conversion. At present, uninterruptible power supply systems (UPS) used at data centers are driven by a direct current. Thus, AC-DC and DC-AC conversions are repeated at least three times including conversion inside the server machine before driving the microprocessor in the server machine.

If the server machine can be directly supplied with a direct current, AC-DC conversion will be required just once.

According to NTT Data, "approximately 10% of power is lost" every time when AC-DC conversion or other process is conducted. Thus, the use of DC power system may reduce the power consumption by about 20% at a maximum, although it depends on the conversion efficiency and the number of times of DC-DC conversion conducted to control the voltage.

Because a data center consumes an enormous amount of electricity, the power that can be saved is considerable, even though the reduction rate is only 20%.

Service to Be Tested in Oct 2008, Launched in 2009

The NTT Group already adopted DC power, for example, for a 48V DC power system used for communication devices.

On the other hand, what NTT Data will test in October 2008 is a data center service using a 380V DC power system.

In many server machines, a 380V direct current is output from an AC-DC converter of a power supply module installed on a rack or the server machine chassis. And the resultant current is immediately converted into a direct current of 12V or lower with the use of a DC-DC converter. Thus, if a DC power system is capable of providing a voltage of 380V, it is more effectively used with a server machine.

However, concerning the 380V DC power service, there are some points that need to be examined, NTT Data said. In Japan, for power equipment of more than 300V, it is required by law to install a device that automatically interrupts electric circuits in the case of electric leakage. In October, the company will start testing the 380V service including the operation check of the device.


Correction Notice: Based on the explanation given by NTT Data Corp, we reported that (1) NTT Data will provide a 48V DC power system from October 2008 and that (2) power systems of 300V or higher is generally prohibited by law in Japan.

However, NTT Data corrected the explanation as follows. First, it is not considering providing a 48V DC power system at the moment. Second, power systems of 300V or higher can be operated if an earth leakage breaker is used. And the company plans to use the earth leakage breaker in the test service.