BLOG: Power Perspectives

[#1]

As I travel around the world I've had the good fortune to interact with some very bright people and see numerous innovative ways to approach power distribution. From different paralleling schemes to unique uses of PDUs at the rack level; what continues to elude me is the direction data centers are heading relative to voltage.

I've seen numerous articles discussing a possible North American migration from 480V to 400V. Much of the rest of the world is already distributing 400V, but this does not stop data center owners globally from wrestling with the same questions about voltage and distribution.

What is the "voltage dilemma"?

As we look for "green" solutions and ways to reduce the cost of operating a data center, it seems like the "voltage dilemma" is gaining awareness.


I'd like to hear from those that follow this blog, your thoughts:

• Is there a "voltage dilemma"?
• Are you looking for manufacturers to address the issue?
• Are you doing something in your data center that solves the "voltage dilemma"?
• Or is this just another passing fad given the high cost of energy today?

 
Please post your input below.

[#2]

The whole purpose of moving to 400/230V is to gain the effeciency from the power supplies and in the distribution. However, in the US we still end up with a transformer in the mix to get from 480V to 400V so biggest peice in the savings (removing the PDUs) is lost. Instead of driving all of the distribution equipment to the power supply voltage, why don't we drive the power supply voltage to the distribution voltage. There is already some movement in the industry to drive universal power supplies from 110-230V now to 110-277V. Check out the white paper that was presented at the fall 7x24 in Pheonix. The white paper and presentation can be found at the following links: http://www.7x24carolinas.org/Fall2010Mtg/277V_Power_Supply_White_Paper.pdf http://www.7x24carolinas.org/Fall2010Mtg/Syska_BBT_277V_Power_Supplies.pdf Scott Ryberg, PE Syska Hennessy Group

[#3]

The objective of the 400V distribution is to deliver more power with less copper by taking advantage of the input voltage range of the electronics that can accept 240V 1ph at the electronic load.

I do not see the advantage of 400V standby generation on site, if 400V delivery is not be available from the utility company.  On site generation voltage that matches the utility delivery voltage simplifies the electrical distribution design and switching strategies.

UPS systems are currently available for 400V. So 400V onsite generation could move 480V -400V transformation the line side of the UPS but this complicates static and maintenance by-pass configurations and creates a challenge for supporting non-critical bus loads.

Power supplies in the electronics that could accept 277V input voltage would be most beneficial. This would meet the same initial objective while also eliminating much on the facility owned transformation.

[#4]

A recent article in the IEEE Spectrum magazine indicated a movement towards DC distribution systems for use in Data Centers in order to save the energy that is lost in converting and rectifying the power for each and every computer.   Duke Energy and EPRI teamed together recently and built a DC powered Data Center in Charlotte, NC and they report a 15% energy savings. 

Also since 120 VAC incandescent lights are on the way out and LED lights seem to be the only alternative - the LED lighting systems will work better with DC power distribution systems instead of a step down transformer in each light fixture.

Maybe Mr. Edison had it right long ago.

[#5]

What is sad here is that even thinking of going to the European standards of voltage, let alone 50Hz will burn thousands of tons more copper from the need to install larger buss services as power supplies, motors and other devices will chew through current just to run.  Higher installation costs is just what we need. Larger wire sizes is super.  I 2 R heat losses, more air conditioning,,, pretty stupid.Then there is the new debate over going DC for everything from data centers to your toaster.  Come on folks, just because we have gotten the hang of DC distribution for Utility design, doesn't mean every house should have an inverter or other foolish step down destroyable electronice contrivance to use the 10KV on the pole to48 or 380 VDC for devices.  I really want my kids plugging in the 380 VDC cord on the vacuum.  There is a sort of valid argument for DC in data centers or other motor environments but the technologies to distribute the various voltages required like +/- 5,  +/- 12, 24, 48 and other required volages to make things run still need a conversion of some kind and all od the threat to obsolete every device you own is quite a shift in the force.  Is this really what we want or need?  Dont we have worse problems ahead than this mess?  Like the other post credits,,, Edison had a point, not the answer.

Gary

[#6]

I firmly believe there is a “voltage dilemma”. Since we are dealing with a worldwide theatre in this discussion, I think it is important to understand what the various voltages mean. A data center may be needed almost anywhere in the world, so there must either be a single standardized voltage/frequency to operate generic data center equipment or there must be a multitude of data center components all trying to do the same job, but powered by many different voltages, phase configurations and frequencies.

Take a look at the voltages used around the world. There are some decent web sites that will show us what country uses what voltage and at what frequency. There is quite a mixture of specifications. There are even places in the world where there is 50 Hz on one side of the street and 60 Hz on the other.

To make the waters a little more muddy……

Quite some time ago, I was involved in a deeply disturbing (but eye opening) plant-to-plant discussion about things that operated on 230-240 volts. The bottom line is that many places in the world have things that work on 230-240 volts, and that is line-to-neutral (or single hot wire). When you wire up something for 230-240 volts in the US, however, it is assumed that the voltage is actually derived from two hot lines - each at 115-120 volts. Overall, the major device being used may not care about the single phase or “two phase” operation, but the control and logic circuits may not share that same flexibility. I believe it is important for us to understand how each voltage is derived – is it single phase, two phase, or three phase?

As was mentioned in the blog, it makes sense to have backup (or even prime power) generators that supply the same voltage, frequency and phase conventions as the local utility supplies. Less transformation equals less waste, less maintenance, and less components.

I do like the idea of driving the power supplies to the use of a higher voltage (like 277). But, if the trend is towards 400 volts/3 ph, 277 volts line-to-neutral may not be a good number. Unfortunately, the power supplies will still have to transform and rectify down to low DC voltage to make the computers work.

There was one thing that lost me. I do not understand how lowering the incoming voltage from 480 to 400 will reduce the copper usage. As I remember, if the voltage goes down, the amperage must go up, and that will drive the need for more copper. Of course, if I have taken something out of context, I must apologize for that snide remark.

Personally, I think a large gain could be made by driving developing countries to a power scheme already being used by others, thus attempting to reduce the number of different power schemes scattered all over the globe.

As long as we are wishing ….. there must be some way to make power transmission more efficient. A huge amount of our power produced is consumed by just getting it from one place to the next! A data center is a prime example of the problem. There are lots of chillers and fans incorporated into the average data center to handle the heat produced by all that number crunching.

[#7]

We are working with a customer who is adamant about a 400 volt system.  For a large data center, he makes a compelling case.  The benefit of a 400V system is you get 3 legs of 230V phase-to-neutral, which many rack devices will run on today with no modifcation.  No need for transformers or PDUs on the floor.  Granted the lower voltage will increase wire cost for distribution, but you will save money in transformers\PDUs.  Plus you eliminate a point of failure and a device that robs you of efficiency and rejects heat.  Most good-sized data centers have incoming voltage of the medium variety - minimum 4,160 and more likely 12,470 or 13,800.  Along with that would typically be a substantial standby power system.  If you've got 4 or more 2MW gensets, it makes no sense to parallel at anything but medium-to-high voltage. 

So, back to the 480 vs 400.  Let's say you've got two 12,470 utility incoming services and six 2MW gensets in a main-tie-main general setup.  Assuming you've sized your gear correctly for fault current, you actually end up with a pretty simple piece of gear that is distributing power to your loads at an efficient voltage.  Now, if you drop, say, 6 pad transformers along the building - 3 sets of A and B - and step down to 400 at those points - you can run those three hots and a (oversized) neutral directly to your UPS, into 3-phase distribution panels (cheap) and into the racks.  No additional transformers rejecting heat into you room and robbing you of efficiency.  It does save real estate and efficiency and reduces component count which increases your uptime curve.  Initial cost is likely similar.  Your generators are still a typical voltage, so no problem there either.  All that said, here's the kicker - not many UPS manufacturers are offering a 400V 60Hz box yet because there's no demand. 

Ideally, if rack devices could be made to operate on 277V (they already do it with lighting) this all gets easier.  You wouldn't think 47 more volts would be a bid deal, but I'm not a server guy so maybe it's a huge deal.  If that is indeed the case, watch out - I can see a drive toward 400V coming. 

Just a note: as stated above in another post - this is a 60Hz problem - in places where the utility is 50Hz we may already be in business.

Cheers!

[#8]

Ladies and gents, I was linked over to this from a friend , so please forgive my intrusion but this is a topic that is the very heart of my industry. I am a lead technical director / "all around Shell answer Man", for the manufacture of modular data centers. In the past, the IT industry, which is comprised primarily of electronic background people, have shied away from higher voltages because of lack of knowledge and safety.

For those of us in the power world, 480/277 Vac is not high-voltage, in the IT industry it is considered to be right on the line between low and high voltage. This rise in industry-standard voltage started at 48 V DC and is now comfortably progressed upwards to the 240 / 230 volt level. For several reasons, it has stabilized at this point, primarily because it is 50/60 Hz universal. It just so happens that the method to derive the 230/240 volts in a standard WYE configuration- is the three-phase line to neutral voltage of 415 / 400. A second choice is to use a corner grounded center tapped delta configuration- which is not standard and is a line to line configuration. Not to insult anyone, but you cant get to 240 VAC single phase in residential service without a transformer. Sorry to drag on here but this 240 V AC  is the reason for the 415 / 400 V AC requests.

Most all IT Rack components run at universal 100-240 V AC single phase and none of the commoditized manufacturers are making power supplies that will accept voltages higher than 250 V AC single phase input. Why? Lots of reasons, strangely the biggest is political, next is physical size and for most it is simply philisophical. This is about to change, but the change that will come, is going to surprise everyone. What we are discussing will follow the same transition as PC's have experienced in the rest of the world, "Why have a laptop or tablet, when I already have a smart phone?".

Most of the future dev discussions is a jump from the current 240 single phase inputs to the IT equipment , not to 277 V AC single phase but a jump up to 480/460/440 three phase V AC to the IT Components and even up to 600 V AC 3 phase input. I can keep going with reason to do this, but the most important reason, not to do it is from the IT person perspective and that is a philosophy that anything above 250 V AC is dangerous. 

There are many arguments for different voltages and configurations, both for AC and DC, but until the equipment can take these inputs directly and eliminate the power transition losses from Transformers or rectifiers there is no real advantage, other than potentially the reduced cost of installed copper. It is also important to remember that we here in the United States have a tendency to think we are leading industry and in reality we are lagging. US engineers are ignoring a lot of the methods to achieve optimization in the data center world hoping that these creative methods will just go away and not negatively impact their business as engineers. EYP learned this the hard way and exists as a financial loss for HP with less than half of their previous staff.  If the data center Industry is able to commoditize the parts and pieces of a data center, of which they are doing so very rapidly, look at the latest Microsoft announcement about a 2nd enterprise class data center in Virginia. Their goal is to control the innovation and future next steps of optimization and economy of the build, without extensive engineering services or costs. 

In the short term of 3-5 years the 415/400 V AC is here to stay, to simply find economy by moving the location of the transition losses, which in some cases does exist. Everything we manufacture is 415 / 400 Universal 60 / 50 Hz and we have never been asked why and the customers install transformers- no questions asked. 

In the long term, Power supplies will change to the highest tolerant 3 phase input voltage that the industry will accept and will have a greater economy and higher efficiency than the single phase SMPS that exists today.

From a build perspective, my bet is that 415 / 400 is here to stay for "traditionalists" in the IT industry, but real progressives will jump at the "higher voltage 3 phase to the device" and crush their competitors by eliminating most of their losses and making big gains in the world of efficiency.

Better, faster, smaller, cheaper thats the criteria.