Hi Mark V experts,

i really need some guide in understanding "TCQA LVDT POSITION DIFF HIGH REG#5" diagnostic alarm in Mark V.

For yesterday only, i have 746 entries ie. ON and OFF.

As u know this is difference from process alarm where u can straight away interpret from logic ie. CSP.PRN file.

So where do i start? How this alarm is generated? What's the setpoint? Which servo regulator is giving this alarm? Is it showing something?

 

The Mark V Application Manual describes how LVDT pairs are associated with regulators. Regulators are also called "servo-valve outputs", so you need to look at the I/O Report or IO.ASG to see which servo-operated device is connected to SVO5 (regulator 5). I believe it's most likely the IGV servo output, and that means that LVDT inputs 9 and -10 are associated with Regulator 5/SVO5, and the two IGV LVDTs should be assigned to these two LVDT inputs.

The Diag. Alarm is trying to tell you that the feedback from the two LVDTs associated with SVO5 differ by a non-configurable amount; many Diagnostic Alarm setpoints are hard coded in firmware and cannot be precisely determined nor adjusted.

The easiest and best way to see the LVDT feedback is to use the AutoCalibrate display. If you start the AutoCalibrate display and open the SVO5/IGV screen, you should be able to see the feedback and voltges from both LVDTs. (Opening the display will cause a couple of nuisance Diag. Alarms because it will read the RAM directly on the TCQA card, but it's just a nuisance alarm and can be disregarded. If the unit is running, you can't do anything with AutoCalibrate, it can just be used as a "viewer" of LVDT information.

Hope this helps!

 

CSA,

checked IO.ASG and confirmed Regulator #5 belongs to IGV.

opened AutoCalibration page as below:

http://www.sendspace.com/file/idjoj4

the servo current seems unstable for R,S and T core.

is that the origin of the diagnostic alarm?

 

dinster,

The alarm is related to an excessive difference in LVDT feedback between the two LVDTs. You didn't provide an indication of which processor is annunciating the Diag. Alarm, or if more than one processor is annunciating the Diag. Alarm. It's kind of like a Voting Mistmath Diag. Alarm, only for the LVDT feedback.

Certainly, there is something driving the servo currents to be unbalanced, but from the display you provided it's not clear why. The reference is the same for all three processors, and the actual position (which is the high-selected value of the two LVDT feedbacks) at the time this snapshot was taken was relatively close to the reference. And, you didn't tell us if the alarm was active when this snapshot was taken (which is pretty important to know).

What is the null bias current being applied to the regulator (from the I/O Configurator)?

What is the IGV reference of each processor, CSRGV? (It's probably equal to the Reference value on the snapshot, but there may be a bias we're not aware of.)

You indicated you have hundreds of alarms in a single day; this seems to mean that the difference is changing for some reason and is bordering on the limit (which isn't known and can't be changed).

I'm also curious about the MAX NEG value; I've never seen an max open IGV angle more than 90 DGA. Unless someone wasn't reading the protractor properly. Can you tell us what kind of turbine this is and what the CSKGVMAX Control Constant is?

I would say that there is a problem with one of the two LVDTs and that it is presently intermittent. Perhaps a loose wire, or sometimes the movable core gets bent and scratches the inside of the armature.

 

The reason of the alarm is,
The difference between LVDT#1 & LVDT#2 is greater than 7,5 degree.
If one of your LVDT is healthy, than you are on the safe side.
As CSA told and in according to logic, machine woks with the highest LVDT value.

When your machine over the part speed, and if the IGV openıng is under 40,8 degree than you will trip.

Also if your machine is under part speed and the difference between LVDT#1 and LVDT#2 is higher than 7,5 degree than you will trip too.