I am going to talk about one of the most important component of electrical power system which is the magnetic contactors so i’ll discuss main parts of the contactor then how the contactor works and finally i will show you the wiring diagram to how to control and energize the electromagnetic contactor.
So the basic definition of the magnetic contactor is a contactor is an electrically controlled switch used for the switching of electrical power circuit so the application of the contactor comes in every every machine in which an electrical motor is used so whenever you have to switch on or switch off any electrical machine you need a magnetic contactor unlike a circuit breaker .
Magnetic contactor does not protect the circuit from overload it is only used to switch on the electrical power circuit so now i’ll discuss the main parts of the contactor this is how an contactor looks like this is a coil normally a coil on the contactor is labeled as a a1 and a2 another main part of the contactor is the main terminal or the main contacts of the contactor the incoming main contacts are labeled as l1 l2 and l3 similarly .
The outgoing main contacts through which any electrical machine is connected are labeled as t1 t2 and t3 and this is a common standard you will find this label on different manufacturers contactor next component is an auxiliary contact this is labeled as 13 and 14 terminal number normally the contractor comes with normally open contact you can also have a normally closed auxiliary contact this is a dry contact what it means that whatever you apply on the input of this contact you will have at the output whenever the contactor is energized the next part is a moving part of the contactor which is also known as .
The plunger whenever a contactor is energized the plunger moves inside the body these are the main parts of a contactor so let us talk about how the contractor works first of all these are the incoming main contacts of the contactor in which you have connected the main supply these are the outgoing main contacts of the contactor on which an electrical motor is connected these are the moving contacts .
Which are connected through this moving core or the plunger this is a coil which is wrapped around this core and this is a core which becomes an electromagnet whenever this coil is energized and these are our auxiliary contact which is also attached with this moving plunger so what happens whenever you apply the control voltage equal to the rated voltage of the coil it will energize the coil.
Whenever the coil is energized it produces magnetic field this magnetic field when interact with an iron core produces an electromagnet which then attracts another core which is connected with this plunger so when it attracts the core towards itself the plunger move down and it will short all the main .
Contacts across each other and after that an electrical machine will be supplied an electrical power through contactor at the same time our auxiliary contact will also change their position that is a normally closed contact will now become open and over normally open contact will now become close and by using this auxiliary contact in our control circuit we can perform different functions on my left side this is a power diagram of a contactor this symbol is used to show a contactor all these contacts are connected .
With the moving part which is controlled by this coil so you need to contact your main phases that is rst or red yellow blue with the incoming main contacts of the contactor and you need to connect the load or an electrical motor or an electrical machine with the outgoing main poles of the contactor between these two.
Between the contactor and the load you need to connect an overload which is used to protect a circuit from overloading this overload can be an electro thermal or an electronic overload so let us talk about the control diagram of this contactor so if you need to energize the contactor what you need to do is that if your overload is not tripped the phase will appear at 96 terminal and since the off push button is closed .
It will now appear at the incoming side of the on push button now you need to press the on push button in order to energize km1 coil of the contactor because the other side of the contactor or the coil is already connected with the neutral this is an on push button what happens when you release .
This button it will again comes to its original position that it opens the circuit so in order to keep the circuit energized you need to put an auxiliary contact of the contactor in parallel to this on push button in order to keep this contactor energized this is also called an holding circuit because it holds the contactor or keeps the contactor energized.
If you want to de-energize the contactor you need to press this off push button which is initially in the closed position so when you press the off push button it will open the circuit and de-energize the contactor so quickly let’s talk about the main specification of the contactor whenever you need to demand the contactor you need to specify these parameters.
First is the switching voltage ac or dc next is the rated current you need to keep an eye on the application of the contactor whether it is used for non-inductive load or the inductive loads then you need to specify the number of main poles there can be three main poles or four main poles of a contactor then number of auxiliary contact.
How many normally open or normally closed contacts you need with the contactor then you have to specify the coil voltage either ac or dc because the contactor coil voltages can range from 24 volts 12 volts to several voltage then the frequency either 50 hertz or 60 hertz and finally the auxiliary contact mounting it can be a side mounted or the top .