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Failing MKV Controllers
Two, <R> and <S>, controllers of MKV system failed simultaneously at base load.

Two, <R> and <S>, controllers of MKV system failed simultaneously at base load. At SOE first alarm was low hydraulic oil pressure, all standby and DC motors started.Trend showed 2/3 TTXD's were down for 1 minute. No additional process alarms prior to the trip. In diagnostic alarms only "power supply P15 out of limits" from <S> controller constantly coming&going. Strangely, no messages about controllers being rebooted or communication being lost.

Controllers statuses, DIAGC statuses and power supply voltages, hydraulic oil system operation were checked and found OK.

What can be a possible reasons for this kind of failure?

Thanks All for thinking.

Jolene,

How many times has this occurred?

Is there an active 125 VDC Battery Ground alarm? Is the ground persistent or intermittent?

Have you replaced the TCPS card of the processor with the intermittent power supply voltage Diagnostic Alarms?

>How many times has this occurred?

At this unit - never.
We had something similar in other unit at the moment of 52AR/AS changeover, when also only two out of three MKV controllers failed and rebooted themselves (including alarms). We connected it to bad settings of AR/AS (which indeed was not so good).

>Is there an active 125 VDC Battery Ground alarm? Is the
>ground persistent or intermittent?

No 125 VDC Battery Ground Alarm at all.

>Have you replaced the TCPS card of the processor with the
>intermittent power supply voltage Diagnostic Alarms?

Not yet.We are going to replace the TCPS card at first opportunity.

Interesting little tidbit of information....

Do the units have <DACA> AC-to-DC conversion modules as back/ups to the 125 VDC supply?

>Do the units have <DACA> AC-to-DC conversion modules as
>back ups to the 125 VDC supply?

Yes, of course.

>Yes, of course.

Did you know that MANY Mark* turbine control systems DO NOT have <DACA>s?

<DACA>s are KNOWN to accentuate any AC input voltage spikes or dips. They are NOT filters. Even the <CPF> filter module is NOT there to protect against issues with input power spikes and dips--they are more to prevent electronic noise from INSIDE the panel from getting out to the power supply(s).

So, if I understand the 52AS/AR comment, if you're having problems during switching of AC power sources (supplies), this can be made worse by the action of the <DACA>s.

<DACA>s are crude AC-to-DC converters--that's all they are. And, if there are problems with the AC power supplying the <DACA>, the output of the <DACA> will actually be worse than the input. There have been MANY sites with <DACA>s that were powered by inexpensive (cheap) inverters--which take DC from a battery and change it to AC with very little filtering or smoothing, which is then fed to the <DACA> which converts it back to DC from AC. But, in the process the <DACA> has been shown to make AC input voltage spikes and dips larger on the DC output.

And, again--battery charger problems can also cause problems, even if the <DACA> input, and output, are fine. The Mark* turbine control does a high-select of the 125 VDC inputs, and if there are spikes or dips of one of the other, that can be damaging to the Mark*. And, lead to nuisance and intermittent problems until the cause is found and resolved.

Please write back to let us know what you find!

0 out of 1 members thought this post was helpful...

>>THIS IS A RECOMMENDATION OF HIGEST PRIORITY!!!!<<<

Replace your battery charger..you're sitting on dynamite.

Jolek,

C^2 has a valid concern--failed capacitors in the battery charger can be very problematic and even destructive (to cards in the Mark V, or Mark VI). And switching power sources can make spikes and dips in voltage output from a battery charger with bad cap's even worse.

And, switching can also cause spikes and dips from a <DACA>, if so equipped.

Battery grounds (which your unit doesn't seem to have) can also make problems worse.

There was a batch of Mark V power supply cards which had capacitors that failed prematurely and can cause nuisance problems, including processor re-boots--usually during times of input voltage disturbance, or battery grounds.

Do have someone familiar with using a oscilloscope use one to check the output of the battery supply, preferrably under some kind of load. You can temporarily start the Emer. L.O. Pump to apply a load to the battery charger; do this while the unit is not running, if possible--starting the Emer. L.O. Pump won't trip the turbine, but if the battery charger and/or one or more TCPS cards are suspect that could result in a situation similar to the one in the original post, which would trip the turbine.

Please write back to let us know how you progress with your troubleshooting!

>There was a batch of Mark V power supply cards which had
>capacitors that failed prematurely and can cause nuisance
>problems, including processor re-boots--usually during times
>of input voltage disturbance, or battery grounds.


CSA:

Can you elaborate on your comment regarding a bad batch of MK-5 power supply cards with bad capacitors? What vintage, how the issue was identified (since you indicate it was intermittent) and how long the issue existed in the field before the actual issue was discovered?

Also, can you elaborate on how the processor reboots are initiated (I believe they will re-initialize at some voltage level but have never seen any literature discussing that)?

MHWest,

If I recall correctly, it was in the early 2000's, and it took a while (maybe a year and a half) to identify the problem, and I think there was a PSB (Product Service Bulletin) or maybe even a TIL about it.

The TCPS cards would emit a high-pitched but low-volume "screeching" noise which was difficult to hear for some people but was very easy to hear for others. And, the noise seemed to start and stop if the temperature in the compartment where the Mark V was located changed by a few degrees (went up and down during the course of a day if the air conditioning couldn't keep up with the heat load in the compartment). Sometimes the screeching noise would vary somewhat in pitch, but not always.

I don't have any PSB or TIL numbers. But I believe there was a revision number change on the TCPS card when the problem was identified.

As for what voltage change caused the reboot, I don't recall ever seeing any published number. My experience was that intermittent and hard battery grounds made the problem of TCPS re-booting worse, as did large, sudden 125 VDC power supply voltage swings--such as when certain devices were de-energized (HGA-style relays (commonly used for 52GX), and compressor bleed valve solenoids and liquid fuel forwarding shut-off solenoids--devices with large inductive kicks). GE provided RC filters to be installed across such device could to help reduce the re-boots, until, I believe the TCPS issue was identified.