contactors

[ONIT]

Evening all

i hope there mite be some one about who can shead a bit of light on contactors.

What are they about and what is its main job, whit in a commerical installation.

All replyes welcome

thanks very much (iam a bit unclear about them)

 

[montybaber]

contactors allow you to switch large loads by energising a coil (can be a range of voltages ac/dc), due to the coil being seperated from the secondary switched load there is very little current drawn and allows the use of PLC's etc (with small power supplies) to switch very high loads (motors etc).

Sorry if thats a crap answer had a few beers

 

[Des 56]

Yes contactors are used to switch large loads
Also by using a contactor to switch the load,it gives you the option of utilising that low current switching of the coil to make a control circuit with various devices like stop buttons limit switches etc that can be included in the control circuit to de energise the contactor

 

[CUDABOY]

basically a big (no swearing) relay,only ac .....stops you burning out the high beam switch when youve just fitted cibie spotlights to your escort capri marina etc......................aaaah happy days.

 

[montybaber]

or dc

 

[CUDABOY]

correct,ac/dc swings both ways....

 

[mrloy99]

i would use contactors regularly to control any number of lighting circuits from only one switch.the main advantage to me is that you can wire all circuits to dist board position where you would locate the contactors.The switch wire can then be broken as required,ie,key switch,timeclock,photocell or whatever the situation calls for.This in industrial situations can save the necessity for multigang switchbanks.Also on for instance,long outside lighting circuits,where it may be necessary ,due to potential volt drop,to have to use large swa cables up to 10mm sq.It would be impossible to
physically get these cables into a normal switch terminal.Generally contactors make a cost effective solution.

 

[jonny1]

ok so if you had, say 5 switch lines at the contactor how would these be connected in the contactor?

 

[mrloy99]

ok so if you had, say 5 switch lines at the contactor how would these be connected in the contactor?

Hi Jonny1 very simply--contactors that I have used come in 2,3,or 4 pole,I haven't come accross a 5 pole-so you could use a 3 pole and a 2 pole mounted side by side on a dinrail in a suitable enclosure.Your neutrals and earths do not need to be switched so these are connected straight thru in suitable connectors.For your lives ,just come straight from your circuit breaker to one of the terminals on the contactor ,and out on the terminal directly below it to the switched circuit,(load)Repeat for other 4 lines.Now the switch(coil)This can either be from an independant "control circuit" or from one of your circuits that you are switching thru the contactor.Take a live from one of your connections coming directly from CB,out to your switch and then back to A1 on one contactor,this is then looped to A1 on second contactor.You also need to take a neutral from the same "switch circuit" toA2,then loop to A2 on second contactor.