Re: [foxboro] [UCE] Re: Motor Start/Stop Logic

Ah, yes, I forget -- picture = 1k words and all that.
      Field
      start
----|--| |---------------------------|---(M)--
    |                                |
    |                                |
    |--|/|-----------|/|---|--| |----|
      Field          DCS   |  DCS    | 
      stop           stop  |  start  |
                           |         |
                           |--| |----|
                               M

Field start/stop is actually one 3-position switch:

Pos             F. Start        F. Stop
--------------------------------
"Start" C               C
"Run"           O               C
"Stop"  O               O

the "Start" is momentary and spring returns to "Run".


Pros:
-------
Can bump motor in field regardless of DCS state
Simple -- doesn't rely on DCS logic

Cons:
--------
2 outputs required & more control wiring.
If field start gets stuck closed, can't stop motor from DCS.


Corey





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01/24/2006 01:56 PM
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[UCE] Re: [foxboro] Motor Start/Stop Logic






We use the FBM just like a field start-stop-light.  Two outputs ... one
driven by COUT_1 is momentary on, one driven by COUT_2 is momentary off ..
and 1 input for motor status.  Sometimes we'll use another input for some
auxiliary data, like vibration.  It seems so easy to me, I don't know why
you'd want to complicate it with all that other stuff.

local DCS    local   motor
stop stop   start    coil
---|/|--|/|--|--| |--|--(M)--|---
|       |       |
|  DCS  |  run  |
| start |  ind  |
|--| |--|--(X)--|
|       |
| motor |
|  aux  |
|--| |--|


Brad Wilson
ExxonMobil Chemical Co
Edison Synthetics Plant
732-321-6115
732-321-6177 fax
Brad.S.Wilson@xxxxxxxxxxxxxx










 
 
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