UK computer power supply config

Hi

I tried to send this as a pdf, but it did not work, so please see the extract from the Department of Trade and Industry in the UK regarding electrical supplies.

Electrical Supply Tolerances and Electrical Appliance Safety

Many of the UK appointed Notified Bodies for the LVD and the UK Authorities remain concerned that with the UK electricity supply being 230 V +10% -6% and much of Europe being 230 Volt +6% -10% and the standards testing at rated voltage +/-6% that there is a small possibility that some electrical equipment may be unsafe at voltages for which it has not been tested. Though this issue is often referred to as a UK problem it is not. The UK is one of about 11 countries in the EEA which have an upper voltage limit of

230 V +10%, with of the order of another 13 scheduled to move to the same upper limit in 2008. There are also a number of countries with lower limit less than 230 V -10%. Though the electrical supply is quoted as being over a range, it is preferable for power distribution companies to keep supply voltages as high as possible to minimise current in the supply network and hence delaying the need to make improvements to the supply infrastructure to increase the current handling capability. There is information suggesting that certain cities in Europe have already pushed the supply voltage up to the upper limit. It is foreseeable that many will take advantage of the option to raise the supply voltage to 230 +10% at an early opportunity. The UK Government is of the view that equipment placed on the market in the UK must be safe at the operating voltages which the equipment will find itself exposed. We remain concerned that the standards may be inadequate by not testing over the full voltage range. We have been informally made aware of appliances which have failed at the 230 V +10% limit - there are also allegations of appliances which have been found to be unsafe at 230 V -10%. But as none of these have been formally referred to Government there has been nothing to investigate. Others in industry are also concerned, though others are not. It was agreed many years ago between the UK appointed Notified Bodies and the UK Government that UK Notified Bodies when assessing products would ensure that the product was safe for all supply voltages that an appliance was liable to be exposed to. The UK Government continues to expect Notified Bodies, when verifying a product, to assess the risks that may be present. The Government considers this to be a risk which should be taken into consideration. We have been advised that this situation is well known by many major UK wholesalers/distributors/retailers and some will not handle products which have not been assessed against the full supply voltage range within the UK. Whereas the concern raised in this notice is with respect to safety alone their concern may additionally be with performance and fitness for purpose.

Hope this helps

BIllB

| I believe that I have seen some posts here regarding data center power in | the UK. I'm curious to find out what input voltage and configuration is | commonly used for single phase computer power supplies in large data | centers. | | In the US, it's common to use switching power supplies with an input range | of about 95 to 240V. This covers single phase voltage of 110V or 220V. It | also allows operation from a 208V 3-phase delta source (line to line). The | same supply could also operate from 400V 3-phase wye with a line to neutral | voltage of 230V. Is this common for the UK? If so, are unbalanced neutral | currents a problem? Are any other configurations common? Thanks in advance.

There are two kinds of SPSs that support international voltages. One kind has continuous voltage support. The other is switched (maybe automatically) and only supports two narrower ranges. This latter kind may not work so well on 208 volts.

Larger computers (using 2 kVA or more) often are designed to operate from

208 volts or 240 volts (e.g. don't even accept 120 volts).

Operating from 208 volts means no current on the neutral since it is not connected to these loads. There will be no neutral harmonics. There will be harmonics on the phase lines, but that will be 2/3 of what would be on the neutral, though double what would be if 120 volt loads were used.

I'd prefer to operate full range (100 to 240 volts continuous) SPSs on a

240 volt circuit. That will give the added advantage of brownout operation, though the average current will go up when that happens.

They should have required the country to switch everything to 240 volts in the latest Energy Bill that will ban glass bulb heaters in 2012 to 2104.

Yes, that's why they are designed for 230V operation.

Neutral conductor is normally at least same size as phase conductors, so there's no problem if the phases are not balanced. (Supply company might not be pleased, but there's no dangerous situation present.) Something which had to be factored in was the harmonic content of the SMPSU's. 3rd harmonic (and multiples) add in the neutral and could require the neutral being sized larger than the phase conductors, although with recent power supplies, that's no longer the case as they are mostly power factor of nearly 1.

Larger computers prefer to run from 3-phase 240V star (or wye as you call it) -- it's easier to build high power SMPSU's with a 3-phase input. Some can take either 3-phase star, or single phase supply.

| Larger computers prefer to run from 3-phase 240V star (or wye as you | call it) -- it's easier to build high power SMPSU's with a 3-phase | input. Some can take either 3-phase star, or single phase supply.

Do these larger computers make connection to the neutral conductor in addition to the three phase conductors and the earthing conductor? Or might they leave the neutral conductor unused and base their circuits on 415V line to line (e.g. a "delta load")?

Similar questions could be asked of larger electrical applicances that connect to three phase power, such as an electric stove. Would heating elements within be wired to 240V or 415V?

All of the mainframe computers I have worked on have been wired 3-phase

240V star. The change from single phase to three phase seems to be around 5kVA. YMMV.

Same answer, although the biggest I have come across was 25kW.

Would you have a link to a company that sells a SMPSU with a 3-phase 240V input?

I may have missed something of significance to our business, would appreciate your trying to email the pdf to me at snipped-for-privacy@lyons.demon.co.uk or the link if it is on the BERR (DTI) website.

Why I'd like it is to see if I need to update the text at

As you may know (this is NOT an advert!) we make energy-saving voltage regulators which provide energy saving (and equipment life prolongation) by controlled voltage reduction.

We currently advise that equipment needs to allow for a supply voltage range of 230V +10% (pretty closely equivalent to the old 240V +6% although for safety UK mfrs used to often test to 240V +10%), down to

230V -14% (the EC norm of -10% plus the old IEE recommendation of up to a further 4% for drops within the consumer's installation). Obviously, except for some SMPS pretty well nothing operates satisfactorily over such a wide range.

I appreciate this is a matter of operational integrity rather than safety as such but they are obviously closely linked.

Many thanks Bill (W)

Is this the sort of thing?

Thanks for the link. We already use a Puls brand supply that runs on

380-480V 3-Ph in and a single output of 48V. They are top of the line as far as switching power supplies go. However, I was thinking more along the lines of a supply that output ATX voltages to power a computer mainboard (5V, 12V, etc.)

-N.Morrow