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manir_b4u2002
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Close / Open in a Control Circuit

02/18/2009 1:40 AM

We know that NO=Normally open,NC=normally Closed,but i want to know what is the exact meaning of CO(close/open) in control ckt?
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JohnDG
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#1

Re: 220kv/33kv SUBSTATION

02/18/2009 1:50 AM

CO = Change Over - a device with one NO contact, one NC and one common.

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Tippycanoe
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#2
In reply to #1

Re: 220kv/33kv SUBSTATION

02/18/2009 11:36 PM

AKA - "Center Off"

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Qqberci
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#9
In reply to #2

Re: 220kv/33kv SUBSTATION

02/19/2009 1:17 PM

Maiden name: Morse contact...

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babybear
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#6
In reply to #1

Re: 220kv/33kv SUBSTATION

02/19/2009 7:07 AM

Hello John,

I think you are correct. But I always took it to mean 'circuit off'.

Anyway, take care.................

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snygolfgs
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#11
In reply to #1

Re: 220kv/33kv SUBSTATION

02/20/2009 7:30 AM

GA!

CO (C/O) is "Change-Over". Guess it depends on where in the world you are located and where the relay was manufactured.

Same as Double Throw.

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Tim in Mexico
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#3

Re: Close / Open in a Control Circuit

02/18/2009 11:42 PM

Well I beg to differ. If you are looking at the question only (close/open) it would be that the circut remains in its last comand possition and does not return in either direction.

Where as a normaly closed device would be closed until energised in what ever fashon it is designed to react with (i.e. pneumatic, electric, hydraulic, etc.)

A Normaly open the same only in reverse...

Ok guys im ready to get beat up over this, ive got broad sholders go ahead
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Grochy
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#4
In reply to #3

Re: Close / Open in a Control Circuit

02/19/2009 12:29 AM

It will depend what country the post is from eg in Australia red button on control circuit is stop and green button is start other countries it is the reverse just as standard labelling is not always a standard but i am going with John "change over" the post was not specific about CO refering to a switch, relay, contactor etc
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Tippycanoe
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#5
In reply to #3

Re: Close / Open in a Control Circuit

02/19/2009 12:30 AM

I think you got it right for a particular device, but other devices may be part of the 'ckt.' with a center off position. If you eyeball the schematic and the parts list it, or put your hands the device you'll get that "Aaha" moment

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Anonymous Poster
#7
In reply to #3

Re: Close / Open in a Control Circuit

02/19/2009 9:07 AM

You are correct as NC & NO applies to a failsafe relay (the "normal" means de-energized). These can be single pole (NO or NC) or multiple pole devices. A latching relay remains in it's last selected position and needs no power to keep it there, so there is no "normally" closed or open position. A closed/open or change/over refers to one (or more) single pole two throw set(s) of contacts.

Check out www.therelaycompany.com for a glossary of relay terms. Many others also under "relay terminology"
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Anonymous Poster
#8

Re: Close / Open in a Control Circuit

02/19/2009 10:47 AM

CO usually is just short for COmmon.
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coconutpete
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#10

Re: Close / Open in a Control Circuit

02/19/2009 6:56 PM

CO stands for change over the control circuit is whatever is used to activate the relay

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Anonymous Poster (2); babybear (1); coconutpete (1); Grochy (1); JohnDG (1); Qqberci (1); snygolfgs (1); Tim in Mexico (1); Tippycanoe (2)

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