Emerson Exchange 365

Automatically Stopping Motor with Fail Active is True

Hello, 

I use DC block to start and stop motor and monitor running status. 

Sometimes, while motor is running (set point equal START, and PV is equal to RUNNING), something electrical happens and the RUNNING status is loss resulting in DC1/FAIL_ACTIVE true after about 10 seconds per our design. 

The status of the DC blocks becomes set point equal START, and PV is equal to STOPPED. The Operator acknowledges the FAIL ACTIVE alarm. 

The problem is sometimes Operator forgets to change set point to STOP, so if some other logic triggers that motor to START, nothing happens because set point is already START. 

Is there a setting in the DC function block I can set such that anytime a fail alarm occurs the set point is set to STOP? Of course I can build some logic to set the set point to STOP if this type of failure occurs, but I would think DeltaV already have something like this. 

Thanks for your help in advance. 

• Fail Active
• motor

DCS Newbie

• 27 Dec 2017 9:54 PM
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3 Replies

• MCrisler

  

  • 28 Dec 2017 2:53 PM

  In the DEVICE_OPTS, you might want to try enabling 'Trip'. From BoL: "When the Trip option is enabled (True) and an Active Confirm is lost for a time greater than TRIP_TIME, OUT_D is set to Passive. The SP_D value must return to Passive to clear the tripped condition. When the Reset Required option is enabled (True), RESET_D must also be set to True to clear the tripped condition."

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• DCS Newbie

  

  • 2 Jan 2018 5:52 PM

  In reply to MCrisler:

  Thank you for response MCrisler

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• Bill Sayers

  

  • 26 Sep 2023 2:08 PM

  I know this is an old post, but does anyone have an answer that works for this issue? I too have the same issue that in a time of panic operators forget to top change the SP to stop to equal the PV so they can start it back up. Am i missing something in the settings of the DC block?

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