Rotary with a 10s kinetic energy store - 97% at full load, 95% at half load. Why?

Hello Ian,
I want to understand the mix between rotary and static UPS systems, I would also like to know what load people typically have on their UPS systems? Since, this also affects how efficeint it is.

I await the answers with interest. Lets take a stab at it for 'data-centres' above 500kVA rated load.
Share = Static 70%, Rotary+battery 20%, DRUPS 10%
Typical load = 65% for an established facility
Typical load after the first year (excl MSN, Yahoo, Google, Facebook et al) = 15-20%

We utilize a high percentage (95%+) of static dual conversion UPS systems and most of these operate between 93% and 95% efficiency. Rotary units have been found to be lacking in the capability to support high harmonic content loads and line interactive provides more exposure to external environment, less robust isolation. DRUPS have a whole set of considerations which are different than previous usages, including the notably short duration of back up support.

Thanks Mark,

What load is running on your UPS systems? I am trying to establish what the real world efficiency of a UPS is since it is affected by load.

Regards

Andrew

Most UPS modules in large N+1 facilities run at 25-35% load (note its the module load not the system load that matters. In 2N facilities this can fall to 15-20%. A typical rotary UPS runs at 96.5% at full load, 94.5% at half load and 90.5% at quarter load. The very best statics struggle to match this at the full load end but have no problem in bettering the low load performance. Eco-mode static are better at all loads but you have to accpet the increased risk of failure.

Great info thanks Ian. Good point on the module power; so we should really be trying to optimise UPS module efficiency at 30% load?

Does anyone use ECO mode (Bypass)? It is a feature that all UPS seem to have these days but I have never heard of a data centre using it.

Yes, UPS efficiency should be optimised at 30-40% load.
As for eco-mode: Few do today. Lots will, in the future. Its just a matter of the technology proving itself robust and the cost of power going up (and up, and up) - 'when needs must'. Old-school codgers like me wouldnt touch it with a barge pole unless pushed - but we are a dying breed.

From my point of view, a bypass type ECO-mode, is a dead born marketing noise.
Just lets remember that over-voltage during a commutation is proportional to the commutating current. And the fact that high current installations definitely have relatively high inductance in their meshes of wires.
V = L *dI/dt
It is work fine with small offline UPS, but with something at MW range, the first bypass triacs fire may be the last. Especially, if for example, you lose only one phase, or short it to the earth.
If you need high UPS efficiency, nowadays you may choose between Symmetra MW and Trinergy. Both are modular and use the effective alternatives to the double conversion. Another possible way may be with the rotary units.

Mikhail - For the record Trinergy is high efficiency because it runs in bypass (eco-mode). All eco-mode systems switch in under 4ms and dont let through any overvoltage to the load outside of the CEBMA/IEE466 ITC curve. Thats not to say they all work or are desireable - I'm just putting the opposite case.

Hi Ian! Maybe I am too conservative, or too expressed by experience of dosens burned out high power UPSes. (Not because of ECO :)).
By the way I meant VI mode of Trinegy not trivial VFD. In this mode, as far as I understand, the Trinegy works most like the delta conversion adding or substracting some voltage for the line, but not with the delta transformer, somehow else.