What is a Contactor ? How does it work ? And how to choose a correct contactor replacement ?

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miss our upcoming videos what is a

contactor a contactor is one of the main

electrical circuit parts which can stand

on its own as a power control device or

as a part of a starter

contactors are used to make and break

power supply lines running to a load

or to repeatedly establish and interrupt

an electrical power circuit

contactors are used starting with light

loads to the most complex machine

control contactors are mainly used with

motors transformers lighting heaters and

distribution panels

and it can be considered as the

intersection point between control and

power circuit because it's controlled by

the control circuit and it's controlling

the connection between power and loads

so you can find the contact to symbol in

both control and power drawings

contactor is used when frequent


or remote

trolling is required

the contactus consists of two iron cores

one is fixed and the other one is

movable the coil and it's an insulated

copper coil located on the fixed iron

core six main contacts for power

connection three are fixed and the other

three are free to move with the movable

iron core these contacts are made from

pure copper and the contact points are

made from special alloy to withstand

with the high starting current and

temperature spring it is located between

coil and the movable core auxiliary


it could be normally open or closed and

it is not designed to carry high load

same as the main contacts it allows us

to make on and off for some light

current loads such as contactors coil

relays timers and many other control

circuit pasts and it is linked to the

contactor mechanism so when the

contactor is energized it will change

its status from normally open to close

and vice versa

how a contact to works when applying the

control voltage on the coil leads a 1

and a 2 a magnetic field will be

generated attracting the movable iron

core towards the fixed core so the

movable contacts which are fixed to the

movable core will move as well towards

the fixed contacts to make a contact and

allow the power lines to run to the load

if we interrupt the control voltage

supplying the coil the magnetic field

will disappear and the force spring will

push the movable parts to back again to

its original position that will lead to

interrupt the power going to the load

how to choose the correct replacement

for a contactor first you have to check

the coil voltage it is the control

voltage which is used to energize the

contactor and you can find it printed on

the contactor between a1 and a2 it must

be same as the used contactor

second check the auxiliary contacts if


how many normally open and close were

used in the old contactor third check

the contactor ating it is the contactor

designed capacity and it is printed in a

table on the contactor if we check this

contact a table it is written from

eighteen point five to fifty six kilo

watt which one is the contactor rated it

depends on your load if your load is a

motor so you have to check the AC three

table then say your power Network

voltage is 400 volt that means that this

contactor rating is thirty kilo watt

thank you for watching