Contactors vs relays.

[La Poste]

Does anyone know why contactors are more expensive than relays?

In my mind they do the same thing in fact relays do more (IE normally on/ normally off terminals) so why the difference in price IE contactors are more expensive, I don't get it.

Thanks.

 

[mark1979]

in my experience contactors switch heavier loads. a 20AMP DP switch is more expensive than a 6AMP switch

 

[SPARTYKUS]

contactor sounds more expensive.

 

[Brightspark2]

A contactor is just in and out though where as a relay switches between normally open and normally closed...


Contactors usually carry bigger loads too...

 

[malcolmsanford]

A contactor will give you lovely "thunk" when it comes in, rather than the pathetic "click" on a relay, you then knew the beast of the contactor was working,

 

[Brightspark2]

In my expericance a contactor is also more dynamic in the sense you can add contacts to the front, thermal overloads to the bottom, interlocks etc etc

Where as a relay is just a relay...

 

[SPARTYKUS]

Hey

just looked it up on Wiki out of interest and it appears the only difference in definition is that in fact as we know, contactors can deal with a higher current. Relays don't

 

[johnboy6083]

Contractors are rated for higher currents, where as relays are usually for smaller loads.

 

[mechelec]

Switching higher currents requires larger contacts and more copper and as we know copper is expensive stuff

 

[Knobhead]

A contactor will be rated to make up to 5 / 6 times it’s rated current and break it’s full rated current. Like a MCB it will have arc control devices. Often additional contact blocks can be added to give N/O N/C contacts for control circuits.
A relay is the weakling little brother.

 

[La Poste]

Do contactors have enough internal resistance on their feed side to be wired straight into a circuit with only a light switch in it?

You know a 6 Amp MCB that feeds a light switch that then feeds the live side of the contactor and then from the neutral side of the contactor a neutral back to the board.

The supply side of the contactor would have a 6 Amp MCB feeding a line into the contactor and then a line out to a lamp/ lamps and then a neutral back to the board to complete the supply circuit.

Basically I want to use a contactor to feed our garage lights off an electric door, the electric door has a small light that illuminates when the door is opened and I want to use this lighting signal to switch on an few fluoro's.

The thing I am worried about is blowing the PCB in the garage door and that is why I am asking if contactors have an internal resistance on the feed side of the device, I would hate to think the contactor would allow enough current through it to blow the garage door control unit up.

So basically what sort of internal resistance are we looking at on the feed side of a contactor, how much current will they let through?

Thanks very much.

 

[Inteificio]

That is what they are designed for Poste.
A small current will flow as they lock in, then none.


IMO a contactor is a bigger relay.