UPS

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m sleem

m sleem

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Today i had a meeting with an UPS's supplier, he says the liebert UPS has a built in static bypass switch to unify the sources when the transferring operation, i'm wondering what are the differences between the static bypass switch and the static transfer switch?
Please correct me if i'm wrong,

The maintenace bypass is a manual override used basically for direct connected online UPS to bypass and maintain.

The static transfer switch is an automatic electronic transfer switch with very high speed operation & particularly used for the critical equipment in hospitals & not for the direct online UPS & the maintenace bypass is optional to be installed.

Static bypass switch??!!!
 
I would get the Liebert one line diagram and go through it a few times.

It is possible the static bypass parallels the UPS output with the utility, but only for a short time period to allow a switching operation with the external mechanical bypass. The static bypass is used during the transition from UPS to mechanical bypass.

There could be (are) different variations on this which is I would go to the Liebert one line and be sure I understood the intended switching procedure.

A static transfer switch would have two sources to select from, the static bypass will parallel across the inverter output with the utility.

The static bypass may also be the failover position if the UPS fails. It may fail to utility on the static bypass. It all depends on the Liebert intended method of procedure.
 
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m sleem said:
Today i had a meeting with an UPS's supplier, he says the liebert UPS has a built in static bypass switch to unify the sources when the transferring operation, i'm wondering what are the differences between the static bypass switch and the static transfer switch?
Please correct me if i'm wrong,

The maintenace bypass is a manual override used basically for direct connected online UPS to bypass and maintain.

The static transfer switch is an automatic electronic transfer switch with very high speed operation & particularly used for the critical equipment in hospitals & not for the direct online UPS & the maintenace bypass is optional to be installed.

Static bypass switch??!!!
Click to expand...

Static bypass switch is common among amny manufacturers.

It operates on a subcycle basis, you can hardly notice the transfer on an oscilloscope trace.

It operates when there is something wrong within the UPS module and transfers the load to the bypass input to the UPS. (Hence the UPS output is always synchronised to the bypass source.) It also operates when there is overload - like some genius trying to start a motor on a UPS - and the UPS detects a high inrush, that is not at a short circuit level yet.

There are all sort of 'maintenance' bypass configurations and they are mostly manual and differ from the above.
 
weressl said:
Static bypass switch is common among amny manufacturers.

It operates on a subcycle basis, you can hardly notice the transfer on an oscilloscope trace.

It operates when there is something wrong within the UPS module and transfers the load to the bypass input to the UPS. (Hence the UPS output is always synchronised to the bypass source.) It also operates when there is overload - like some genius trying to start a motor on a UPS - and the UPS detects a high inrush, that is not at a short circuit level yet.

There are all sort of 'maintenance' bypass configurations and they are mostly manual and differ from the above.
Click to expand...
From all opinions i could understand the UPS is always energized?!!
 
m sleem said:
Can we discuss the applications of the offline UPS?
Click to expand...

A new operating mode recognized by the Dept of Energy (Energy Star) and Green Grid as Eco Mode which is essentially a double conversion UPS running in off-line mode (in static bypass). When power quality is detected to be unacceptable, it transfers to the double conversion mode.

You can also get little desktop and small floor mount UPS's that are offline.

Very energy efficent.

http://www.datacenterdynamics.com/f...eco-mode-great-there-are-some-things-consider

http://www.geindustrial.com/criticalpower/images/GreenGrid_WP48-_Evaluation of Eco Mode in UPS.pdf
 
ron said:
A new operating mode recognized by the Dept of Energy (Energy Star) and Green Grid as Eco Mode which is essentially a double conversion UPS running in off-line mode (in static bypass). When power quality is detected to be unacceptable, it transfers to the double conversion mode.

You can also get little desktop and small floor mount UPS's that are offline.

Very energy efficent.

http://www.datacenterdynamics.com/f...eco-mode-great-there-are-some-things-consider

http://www.geindustrial.com/criticalpower/images/GreenGrid_WP48-_Evaluation of Eco Mode in UPS.pdf
Click to expand...
Good, keeping the ups offline in eco mode will not apply any reduction due to the efficiency & aside from that, the continous operation of the online ups will cause a reduction of the efficiency due to life time of the electronic elements.
 
weressl said:
...............................

There are all sort of 'maintenance' bypass configurations and they are mostly manual and differ from the above.
Click to expand...
I tuned my memory & found an old single line of the ups with a static bypass, From the below sld, do we need an extra mechanical bypass for maintenace? if yes, why do we need where the static bypass could perform the same function!

UPS.jpg
 
In that one line diagram, the maintenance bypass breaker may be key locked off with no key in the lock. The key is in the static bypass lock. Going to onto static bypass may release the Kirk key held by the static bypass, necessary to unlock and throw the maintenance bypass breaker.

A multi module configuration would have a different switching procedure. The switching instructions would have to be as specified by Liebert.
 
__dan said:
In that one line diagram, the maintenance bypass breaker may be key locked off with no key in the lock. The key is in the static bypass lock. Going to onto static bypass may release the Kirk key held by the static bypass, necessary to unlock and throw the maintenance bypass breaker.

A multi module configuration would have a different switching procedure. The switching instructions would have to be as specified by Liebert.
Click to expand...
In this case, we would have three current paths from left side as follows:

1. Automatic path through the online ups during normal condition.
2. Automatic path through the static bypass when the ups fails.
3. Manual path through the optional path when we need to maintain either the ups or the static bypass.

Am i right in this sense?!!
 
m sleem said:
In this case, we would have three current paths from left side as follows:

1. Automatic path through the online ups during normal condition.
2. Automatic path through the static bypass when the ups fails.
3. Manual path through the optional path when we need to maintain either the ups or the static bypass.

Am i right in this sense?!!
Click to expand...

Yes, the Manual bypass is often referred to as the wrap around maintenance bypass, so the complete UPS module can be taken offline for service with no energized parts in the module. It would also allow you to loadbank the UPS module with the critical load safely on some other source, such as generator. While loadbanking, you could test the functionality of double conversion to static bypass, without the critical load being in jeopardy.
 
ron said:
Yes, the Manual bypass is often referred to as the wrap around maintenance bypass, so the complete UPS module can be taken offline for service with no energized parts in the module. It would also allow you to loadbank the UPS module with the critical load safely on some other source, such as generator. While loadbanking, you could test the functionality of double conversion to static bypass, without the critical load being in jeopardy.
Click to expand...

"without the critical load being in jeopardy" except that is not being supplied from a UPS source. All these schemes lost the focus of NEVER letting the critical load be left alone without backup power and instead shift the focus onto testing and maintaining the UPS.

There are tomes written about reliability issues with batteries themselves, which is the WEAKEST part of the entire UPS. After Exide decided to separate their battery business from the UPS business there were no UPS manufacturer left that would take responsibility over their entire package, inclusive of the batteries. Third party battery monitoring companies emerged to somewhat assure that you get forewarned of impending battery failure. No UPS manufacturer hopped on board. Monitoring the health of your batteries and weeding out infant mortality
suspect is essential, especially in cheaper battery systems, such as VRLA. While you are replacing your faulty battery, you are still without UPS protection, so you may opt for a second battery bank.

Redundant UPS's often have a single common failure point so they still remain vulnerable. I choose a dual UPS installation where each UPS (with an online bypass) feeds a separate power supply to each control system where dual supply exist. Where only a single supply point exist I either double up the DC supply with a blocking diode or a small static switch between the two AC power sources into a single input.
 
weressl said:
"...........I choose a dual UPS installation where each UPS (with an online bypass) feeds a separate power supply to each control system where dual supply exist. Where only a single supply point exist I either double up the DC supply with a blocking diode or a small static switch between the two AC power sources into a single input.
Click to expand...
If the below SLD is what you meant, how the online bypass will be?

DUAL UPS.jpg
 
ron said:
For some basic topology info, see the attached link. The wraparound bypass is shown simplistically on Page 4 of the pdf.

Almost every manufacturer has a similar primer.

http://pqlit.eaton.com/ll_download_bylitcode.asp?doc_id=21590
Click to expand...

Unfortunately the UPS 'industry' is focused on IT, not process equipment. These papers are 'dumbed-down' to IT 'technical managers' level who knows didly-squat about relability from the configuration and control topology viewpoint of electrical circuitry.

Nowhere in this White Paper do they address MTBF, MTTR, single/common point of failure, battery rliability or the pros and cons of the various configurations. They love the latest buzz-word 'hot-swappability' but never say a word about what happens when the rack bus shorts. The writers have NO operational experience to draw on.

The paper has about as much value as the 'paper' it is written on.....Actually, its value is negative, because IT managers will take it as the sascred word, install systems based on it and never know what hit them.
 
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