Contactors

[new]

hello… i am new here so hi to you all.

I am in my 3rd year of my apprenticship.

I have a question that i seem to be getting confused about (not collage related) we work in some industrial properties most of the time and the lighting is switch via a contactor.. i understand the coil pulls in and contact in act but the switching part i am confused

Can i draw a diagram of how i think it works?

 

[new]

Posting pics

are these correct regarding my previous post ?

 

[Marvo]

Your first two drawings are confusing me with your neutral arrangement but your last one looks promising if you're switching the neutral through the contactor as well as the three phases and assuming the contactor coil is 230v.

 

[new]

ok.. N just there for show. won't switch the N then? also is it best to use the live going to the switch from L1 or use a separate mcb?

if i wanted to use a 0.50mm cable to switch a load of say 32A ?

 

[Marvo]

MCB's are sized according to the current carrying capacity of the wiring so if the control wiring (the wiring going to the switch and to A1 and A2) is capable of carrying 32 Amps then you could, in theory at least, take your supply from L1.

If you're using 0.5mm control wires then you'd need to supply the control side from a 6A MCB.

 

[tazz]

Maybe this will help, photo showing 3 phase switching and single phase....the idea with the contactor, is to switch high current loads, from a low current switch, timeclock etc. So for instance, our switch could be on a 6A lighting mcb, and the contactor supply(s) may be 20A supplying flood lighting

 

[new]

can't see a pic

 

[tazz]

The forum is playing up asking for security codes

 

[Darkwood]

College really need to teach you how to spell college and to draw a wiring plans/diagrams you have mixed 2 methods there and caused confusion but that aside you normally have independent O/L protection for your lighting circuits and dedicated control circuit, this then avoid a fault on a lighting circuit taking out the whole lighting because the control may be borrowed from the circuits thats at fault, having said this on smaller projects this isn't as crucial.

If I've time tomoz Ill draft a simple to follow diagram for you unless our resident Tony pulls one of his on file diagrams out.

 

[Darkwood]

EDIT..... went for a leak before hitting post and seems you have been given all the help you need, can't edit post as forum still playing up at moment so had to add another post.

 

[Pete999]

"Youtube" "how does a contactor work" simples

 

[PEG]

Bollokynoodles,typed out a lengthy missive and it dissappeared....anywho...My shortened advice to the OP would be to assemble some DPST contactors/relays,of as many contact groups as desired,and make up a test board,controlling whatever is to hand (lamps,buzzers,small motor etc) and experiment. Practice drawing out circuits and try to include NO and NC operation,maybe an interlock or two. I am unsure if they allow/use this method at college these days,but it is how i did,and still do get an understanding of a process. At his stage,and with it powered off a 3A plug-top,it should provide hours of fun.