UPS Installation - Rotary V Static

[CJFlatters]

Does anyone have experience and / or useful advice regarding large rotary / static UPS units.

Currently considering two 650kVA units arranged as n+1 configuration, based upon diesel / rotary units.

I have been advised that some data processing loads (servers) can operate with a leading PF which static units dont like though rotary units can cope with easily (ie a synchronous generator).

Any ideas / comments / advice ????



_______________________________________
Regards -

Colin J Flatters
Consulting Engineer & Project Manager

 

[ScottyUK]

Hi Colin,

I'm sure this is the first of many replies, but in my opinion if the client has the money to pay for a pair of rotary UPS's, they will offer superior performance when compared to a static unit with a standby diesel generator feeding the rectifers. Rotary types cope better with leading PF loads as you say, and have much better fault-clearing capability than an equivalent static type. Statics running on battery without a bypass supply available can struggle to trip breakers before they shut down to protect themselves. Treat manufacturer's claims regarding fault-clearing capability with a healthy degree of scepticism. Performance of the rotary types with a distorted load current is arguably better than statics too, although the difference should be trivial when compared to a decent static unit.

Downside of rotary types is higher capital and maintenance costs, although if you factor in battery replacement every five years for a static unit the financial gap closes somewhat over the lifetime of the system.

Who are you considering for the rotary units?



----------------------------------

If we learn from our mistakes,
I'm getting a great education!

 

[CJFlatters]

Thanks Scotty

Had already considered the 'Harmonics / Power Factor' issues in my discussions with the client, but had completely forgotten to mention the major chesnut aka fault
current.

Completely F###s up the existing 'rotary based' design with regard to protection grading.

Have been discussing the job with Piller UK - Do you know of any others ???

_______________________________________
Regards -

Colin J Flatters
Consulting Engineer & Project Manager

 

[ScottyUK]

Company called Eurodiesel made some top-notch units which were very popular with the major financial institutions. Last I heard, the Seghers Group sold the Eurodiesel operation to GE. GE seem to have been buying up quite a few 'names' in the UPS market in recent times - they also bought IMV to gain a static UPS product.

I guess they are still using the old website for now.

http://www.euro-diesel.co.uk

Caterpillar have an interesting-sounding unit of which I have no experience at all, but the web link is below:

http://www.catups.com

Finning are the UK agent for Cat.


Protection grading is a nightmare with static UPS on battery, and tricky with rotaries. Good luck!



----------------------------------

If we learn from our mistakes,
I'm getting a great education!

 

[CJFlatters]

Thanks chaps

Appreciate the help, will follow up the alternative leads, have already spoken to HiTec who have also been helpful.

_______________________________________
Regards -

Colin J Flatters
Consulting Engineer & Project Manager

 

[alehman]

I think it's hard to say which is better in general. It depends on the application. A few pros and cons..

Static UPS:
1. Huge installed base with lots of experience. Trained maintenance and parts readily available in most areas.
2. It is "static". There are no moving parts to worry about except fans and circuit breakers.
3. Made of electronic components with their inherent propensity for hidden faults and sudden unexpected failures.
4. Static bypass circuit provides fault clearing capacity.
5. Typically uses batteries for energy storage which are always a maintenance issue. Can also be a reliability issue if not properly maintained. Large batteries can be an environmental concern.


Rotary UPS:
1. Higher inherent fault clearing ability.
2. Fewer electronic components to fail unexpectedly.
3. Larger than comparable static system.
4. Intertial system typically have less stored energy than static systems means shorter ride-through and less time to get backup E-G started.
5. Systems tend to be customized rather than off-the-shelf which can mean longer acquisition time and more difficult maintenance.
6. Rotating parts need periodic maintenance, subject to unbalance and bearing problems (some use magnetic bearings).
7. More costly than static systems.

 

[mpparent]

Also, to add to alehman's great list, static UPS systems require cooling in the room they're installed in, and from what I'm told, rotaries require little or no cooling.


Mike


PS I've heard of some folks using rotary systems coupled with batteries as well. Something else to think about.

 

[ghazelip]

I'm looking for a magnetic bearing expert to comment on the usefullness of a patented technology that measures forces with an optical strain gage in a magnetically levitated bearing. Strain gage is located in various configurations, typically at the poles. Reference patent #6,518,770. I'm performing a technology assessment as part of a graduate course.

Locally, in Austin, TX Active Power builds Rotary UPS. Can't comment on their use, not familiar.

 

[itsmoked]

ghazelip.. Potted tomatoes are nice.

That should be its own post.

 

[hmchi]

Another issue not mentioned above --- Overall energy efficiency.

Both conventional static UPS and dynamic rotary UPS consume a lot of power in standby mode. When you compute this energy loss [and the cost of removing the heat, especially in tropical installations] into dollars and cents, bearing in mind that the loss is incurred 24 hours a day, 365 days a year, the costs really go up ...

The trouble is --- most specifiers are only there to build the system, not to use it and live with the high operating costs. Thus rarely is this efficieny issue taken into consideration during purchasing decisions.

For better UPS efficiencies, see

http://www.sandc.com/products/purewave/ups_1250.asp

 

[mc5w]

A rotary UPS is about a century old technology and if your load can withstand the frequency dip while the diesel engine is cranking up, these are absolutely satisfactory.

Back in the 1920s when grandfather was earning college tuition by working in paper mills in Wisconsin, each paper making line had all synchronous motor that ran off of a motor, flywheel, generator set. An elelectrical transfer switch was used to switch to the alternate source. The synchronous motors in the paper making machine were designed to tolerate the voltage and frequency droop while a standby generator was cranking up.

A lot of these mills had cogeneration because of the process steam requirements - if a steam engine generator failed the flywheel gave them time to switch to the spare generator. I think that the steam engines ran in parallel with the utility as well and if the utility crashed the cogeneration needed time to disconnect from the utility and then reclose the local bus breakers.