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Gopikrishna Bathula
01-03-2014 11:54 PM

Doubts on I/O Count, Smart MCC, Motor control Philosphy..

Dear All,
Here i am posting a very basic questions which i couldn't get when i searched in internet or in books. I being very new to my profession not aware of these things which i often face in my work. Please spend some time for answering my questions or showing me a way by referring some good material or books.

In my work i often happen to count I/O's as you may be aware that I/O count are the basic things for Controls system vendor to quote his bid.

In the process of counting i am very clear with I/O count with respect to instruments like control valves, transmitters etc but when it comes to I/O count W.R.T Motor i am really very confused.

I am in a project in which only a motor control philosophy document is made on which i have to make motor schematics for P& ID's and also should give my total I/o count to my Control system vendors so that they can bid for my project.

There are some motors with features like :

1) Automatic Change over between running and standby motors
for this i have considered one DO for a running motor & considering nothing for standby motor

2) Dry run Protection
considered one DO

3) Variable speed drives
considered one AO(Setpoint) and one AI(feedback).

4) Various trips( from DCS and SIS) that are coming to motors.
for this even though there are many trips that are coming from many origins i have considered only one DO because there will be only one final effect even tough there are many causes
I have considered I/O counts for Trips separately with respect to DCS and SIS.

5) There is DCS Stop.
One DO

6) There is only Local start and no DCS start.
No I/O Count

7) Apart from this i have considered few DI's for MCC Incomer's open or closed status
I really dint understand anything about this just considered blindly from my electrical dept inputs. Can anyone tell me about this?

Can anyone tell me whether my above considerations are correct?
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Please guide me regarding Smart MCC too which i am not aware as i am from instrumentation and don't have basic electrical knowledge.

when i consider a Smart MCC will there be interposing relay panel?

my understanding is that for a conventional MCC there will be interposing relay panel and all the motor signal will be hardwired.

where as for a Smart MCC there there wont be any interposing panel and and all signal of the motor will be soft linked to DCS by which we will save save lot of wiring.

Is my understanding correct?
Please respond to my questions and don't get scared to see these many question at a time. I have collated all my doubts with respect to motors Control at one place hoping to get a clarity.

Thanks in advance.

With Regards,
Gopi.