contactors and relays

Here's the definition of a contactor from BS EN 60947-4-1:
mechanical switching device having only one position of rest, operated otherwise than by hand, capable of making, carrying and breaking currents under normal circuit conditions including operating overload conditions
NOTE 1 Contactors may be designated according to the method by which the force for closing the main contacts
is provided.
NOTE 2 The term "operated otherwise than by hand" means that the device is intended to be controlled and kept
in working position from one or more external supplies.
NOTE 3 In French, a contactor the main contacts of which are closed in the position of rest is usually called a
"rupteur". The word "rupteur" has no equivalent in the English language.
NOTE 4 A contactor is usually intended to operate frequently.

However the corresponding standard for relays (60947-5-1) doesn't have a definition!
It (60947-5-1) probably doesn't need a definition (and might, indeed, be a redundant Standard!), since I'd be hard pressed to think of any relay that would not qualify as a 'contactor' per the above 60947-4-1 definition! [NOTE 4 is clearly going to have plenty of excpetions, no matter what one calls the device]

Kind Regards, John
 
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And further, just to confuse the issue even more, there are relays dealt with by a totally different IEC committee, TC94. These tend to be (but not exclusively) smaller relays such as the plug-in and printed-circuit types. Their basic standard is 61810, which has the following definitions:

3.2.1
electrical relay

device designed to produce sudden and predetermined changes in one or more output circuits when certain conditions are fulfilled in the electric input circuits controlling the device
[IEV 444-01-01]
NOTE 1 For the purpose of this standard, output circuits are contact circuits.
NOTE 2 For the purpose of this standard, the term “coil” is used to denote “input circuit”, although other types of input circuits are possible.
3.2.2
all-or-nothing relay

electrical relay, which is intended to be energized by a quantity, the value of which is either within its operative range or effectively zero
NOTE "All-or-nothing relays" include both "elementary relays" and "time relays".
[IEV 444-01-02]
3.2.3
elementary relay

all-or-nothing relay which operates and releases without any intentional time delay
[IEV 444-01-03, modified]
3.2.4
electromechanical relay

electrical relay in which the intended response results mainly from the movement of mechanical elements [IEV 444-01-04]

There are several more, but you get the picture!
:confused:
 
And furthermore, many manufacturers have products which look identical to their contactors but are marketed as relays. These tend to be called "auxiliary relays", but are better know in mainland Europe as "contactor relays".

To the OP, are you sorry you asked yet? :D
 
And furthermore, many manufacturers have products which look identical to their contactors but are marketed as relays. These tend to be called "auxiliary relays", but are better know in mainland Europe as "contactor relays". To the OP, are you sorry you asked yet? :D
I think I can but refer back to my very first response to the OP - it doesn't really matter a damn what one calls them, provided the specification is appropriate for one's application!

Kind Regards, John
 
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it doesn't really matter a damn what one calls them, provided the specification is appropriate for one's application!
Quite, as long as the specified information is appropriate for the application, and is complete - the requirements for specification are slightly different.
 
Quite, as long as the specified information is appropriate for the application, and is complete - the requirements for specification are slightly different.
In what ways to they differ? The answer to that might conceivably give us some insight into what they consider to be the difference between a relay and a contactor!

Kind Regards, John
 
In what ways do they differ?
Couldn't easily tell you. The difference isn't necessarily anything physical about the design and construction. If a manufacturer has a product that meets the requirements of the contactor standard, then he sells it as a contactor. If it meets the requirements of a relay standard then he sells it as a relay. If it meets the requirements of both standards then he can sell it as either, or both. As you said, it doesn't matter what it's called if it's suitable for the application.

Many years ago I asked the marketing manager of the market leader for contactors exactly this question. His reply was that a contactor was rated for motor duty, a relay wasn't. Shortly after I came across a standard for motor-rated relays! Maybe he should have said that a contactor was rated for motor duty, a relay wasn't necessarily.
 
Couldn't easily tell you. The difference isn't necessarily anything physical about the design and construction. If a manufacturer has a product that meets the requirements of the contactor standard, then he sells it as a contactor. If it meets the requirements of a relay standard then he sells it as a relay. If it meets the requirements of both standards then he can sell it as either, or both.
Fair enough. I was rather hoping that you might be able to explain what characteristics could make a product satisfy one of the Standards but not the other - since that might have helped us to understand what distinction the writers of the Standards had in their minds. However, it sounds as if you probably can't.
As you said, it doesn't matter what it's called if it's suitable for the application. ... Many years ago I asked the marketing manager of the market leader for contactors exactly this question. His reply was that a contactor was rated for motor duty, a relay wasn't. Shortly after I came across a standard for motor-rated relays! Maybe he should have said that a contactor was rated for motor duty, a relay wasn't necessarily.
... unless, of course, you had been able to find a 'contactor' which clearly wasn't rated for motor duty (I suspect you could have done), in which case both parts of his assertion would have been wrong, and in need of qualification! Whatever, I think that such things probably 'say it all' :)

Kind Regards, John
 
... unless, of course, you had been able to find a 'contactor' which clearly wasn't rated for motor duty (I suspect you could have done), in which case both parts of his assertion would have been wrong, and in need of qualification! Whatever, I think that such things probably 'say it all' :)
Yes, I certainly could have found plenty of contactors rated for distribution duty, or capacitive switching, or several other utilisation categories.
The answer to the question is really that there is no answer!
 
NOTE 3 In French, a contactor the main contacts of which are closed in the position of rest is usually called a
"rupteur". The word "rupteur" has no equivalent in the English language.
It does actually.

Contact breaker.



 
Thanks BAS, I'll pass your comments on the the Working Group responsible for IEC 60947-4-1!
 
It actually makes perfect sense as a term for a NC relay/contactor.
Well, I suppose the sense would be perfect if we called a NO relay/contactor a "contact maker".

I think relays got their name because they were (literally or almost) first put to widespread use as a means of extending the range of telegraphy, using them as 'amplifiers' to 'relay' the signal, at a usable level, from one intermediate point to the next.

Kind Regards, John
 
It actually makes perfect sense as a term for a NC relay/contactor.
True, it does. I think the purpose of the note is just to point out that it isn't a commonly used term in English.
In Germany a normally-open switch is called a "closer" and normally-closed is called an "opener".
 
That can't be right.

Surely the German words would be electricallyoperatedautomatedmachineforclosingcontacts and electricallyoperatedautomatedmachineforopeningcontacts ?
 

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