Frame v mark vie control system having input supply 125 vdc through battery charger and DACA. EOP was started from MarkVIe and stopped the same. During EOp stop command given, after 200 mili second interval of off command Control supply 125vdc dropped up to 105 vdc. P125vdc is reaching 40 vdc and N125vdc is -63 vdc. G125vdco is reaching up to -20.

We have checked EOP on only DACA. 125vdc isolated from charger and 125vdc input MCB put off from mark vie. No voltage dip was observed on DACA. Only dip observed on 125vdc direct supply system.

One more activities done, EOP checked on only battery and dip observed up 90vdc.

Kindly give the idea to resolve the problem.

 

VKGUPTA,

Was the Mark VIe provided with a new GE-design Frame 5 heavy duty gas turbine, or was it an upgradation from an older turbine control system?

How long has this problem been occurring? Since commissioning of the Mark VIe? Has it just start recently?

You post is unclear. A DACA is only provided to power the Mark VIe <b>ONLY</b> in the event that the 125 VDC battery supply is lost or very low. The DACA is <b>NOT</b> intended to power the EOP motor. So, if you're using the DACA to power the EOP motor, that ain't right.

You talk about START and STOP signals given to the EOP motor starter. Are "these" START/STOP coming from the Mark VIe? If so, are the START and STOP independent discrete outputs (one to START, and one to STOP, the EOP)? Or is it the typical GE-design single discrete output used to both START and STOP the EOP?

Where is the power for the EOP motor starter control circuit coming from? From the EOP motor starter, or is the Mark VIe providing the 125 VDC to the contactors of the EOP motor starter?

Again, it's very important to understand whether this is a control system upgrade or a new unit Mark VIe. Also, we need to understand how the EOP pump motor is being powered, and also where the power for the EOP motor starter contactors (the control power for the starter) is coming from.

 

Thanks a lot for quick response.

This is a new installation of BHEL Frame-V machine with Mark-Vie control system.

This problem was appeared recently during EOP test run. DC charger is powering the Mark-Vie control system and EOP also. Yes, start/stop of EOP given from mark-Vie through "L4QEX=1" (Start), "L4QEX=0 (Stop). No independent Discrete output is provided.

EOP motor starter control circuit power is coming from DC charger. Mark-Vie is providing a potential free contact to EOP control circuit.

Again we are mentioning our problem: (Mark-vie 125VDC input supply dropping during EOP Stop command).

EOP Test run was carried out on followings:-

A) When battery charger is powering the Mark-Vie control system, EOP started by forcing of L4QEX=1 from Mark-Vie. During L4QEX=0 (Stop) given, observed that Input supply M125VDC is dropping up to 105VDC for 200 milisecond and normalised after that.

Power supply readings are:<pre>
Variable Before EOP Run During EOP start During EOP Stop
M125VDC 128.2 VDC 123.0VDC 105.0VDC
P125VDC; 64.1VDC 62.0VDC 53.1VDC
N125VDC; -64 VDC -61.0VDC -62.0 VDC
G125VDC; -0.08 -1.3 -20.02</pre>
B) When 125VDC Input supply of Mark-Vie is isolated from DC charger and EOP test run carried out on DACA. Observed No drop in Power supply readings are:<pre>
Variable Before EOP Run During EOP start During EOP Stop
M125VDC 115.2 VDC 115.0VDC 115.0 VDC
P125VDC; 58.1VDC 58.0VDC 58.1VDC
N125VDC; -57 VDC -57.0VDC -57.0 VDC
G125VDC; -0.08 -0.09 -0.09</pre>
C) When DC charger is isolated by electrical and Mark-Vie input supply powering on only Battery. Observation are in readings:<pre>
Variable Before EOP Run During EOP start During EOP Stop
M125VDC 115.2 VDC 113.0VDC 90.2.0 VDC
P125VDC; 58.1VDC 56.0VDC 40.0 VDC
N125VDC; -57 VDC -57.5VDC -50.0 VDC
G125VDC; -0.08 -0.09 -30.0</pre>
Kindly guide us to resolve the problem.

 

VKGUPTA,

I've been thinking and thinking and thinking about this. I think, there's too much we don't know about the equipment being used at the site.

I think there is naturally a large inductive kick when the DC contactor of the ELOP motor starter opens. I think the inductive kick causes some kind of interaction with the battery and the Mark VIe power distribution modules (which have thyristors to shunt inductive kicks).

I think someone has a LOT of time on their hands to be testing this and observing the phenomenon.

I can't explain why there is seemingly a larger voltage dip and a ground when the battery charger and the DACA is isolated--that's really odd. But, again, there's just too much we don't know about the motor starter's configuration, the DC motor being used, the load on the DC motor, the type of Mark VIe power distribution module(s) being used, and the battery charger being used.

I've learned over decades that many times bad installation and commissioning practices cause premature weakening of printed circuit cards which can cause problems like this to appear when extraordinary testing methods are used. Bad practices like powering the Speedtronic with the battery charger only because the batteries weren't installed yet; or failing to properly ground the panel before energization because of rushing to get power on the panel as quickly as possible; etc. To me, the testing seems above and beyond usual, and without a lot more information--which we'll never get--it's too difficult to say with any degree of certainty what the issue might be.

Please write back if you resolve the issue.