what is contactor/ What is add on block?/ and Applications


Contactor there is an automatic switching device. Which is used for automatic switching of any motor supply. It is typically used to convert the motor supply from starter to automatic delta. 



It is mostly used in the panel of the machine. Which plays an important role in making any machine automatic. By the way, there are many companies making Contactors. Out of which the main companies are Schneider, Havells, L&T etc. 


Application of Contactor?


1) Automatic running of motor on star and delta 
2) Automatic on and off of motor 
3) Automatic interlocking in a panel  

Why contactor is used to start any motor? 

Whenever a 3 phase motor runs, it is run on star connection for the first few seconds until that motor comes to its full RPM. And after it comes to full rpm it is run on delta connection.  


Contactors are used to switch the supply from star to delta connection. The contactor abruptly switches the supply to the motor from star connection to delta connection, the process being fully automatic. This is done with the help of commands from the timer on the panel. 


For automatic on and off of the motor  


Contactor Automatic on off any machin It plays a very important role in doing this. If we want to turn on or off a machine for a specific time, then it can be done by making an automatic panel, suppose we have two motors. And out of those two motors, we have to run only one motor at a time. And if we turn on the other one, it should not be on. We can do this type of interlocking with the help of contactor. 

Use of Contactor for Automatic Control  

Contactor is generally used to make any panel automatic. For which we add a terminal block to control the Contactor on some other side as well. Which we call Add on Block. This add-on is pressed with the push button in the blog contact. It is mounted on top along with that push button. NO and NC are thermal on add on block, from which we connect the circuit. 


Terminal and button informatio on Contactor  



Contactor has automatic push button. Which you can also press manually. But when you press it and release it, it will come back to its place. And the contactor will be off. Meaning that when the button of the contactor is pressed, its terminals will be connected to L1 L2 L3 and T1 T2 T3, but when the button is not pressed, its terminals will remain separate from each other, due to which the motor will remain closed. In this process, a separate supply is provided for automatic pressing of the push button. The supply of which keeps the push button pressed automatically. And this position of Contactor remains constant. 

How to turn on the Contactor? 

Now we know that to automatically turn on the contactor, electrical supply has to be given. Which is 220 bold and 50 Hz. The points of supply in the contactor are A1 and A2. From where we can give supply to the contactor. The supply of neutral is given in A1 and phase in A2. Due to which the contact will be on. 


What is add on block? 


Add Unblock is used to make any machine automatic. With the help of which any contactor is automatically turned on and off. Add on block has two terminals, No terminals and NC terminals. These blocks are mounted on push buttons above the main contactor. The add on block has two terminals, it is further connected to the star contactor to switch on the second Delta contactor.  





Add on block is used to turn on or off another connector. For example, suppose we are running a motor, which is running on star and delta. Star has a separate connector and delta has a separate connector. There is an add on block above the star. In that the supply of the add unblock is going to A1 of the delta connector. That is, when the star contactor will be on and its push button will go inwards, then the terminal of the add on block will also be off, which will not supply the delta connection. 


As soon as the star connection contact is off, its push button will come out, due to which this add on block will start supplying to the delta contactor and the delta contact will come on. Similarly add on block is used. To turn on another contactor. 


What is NO and NC in Contactor? 

There is NO and NC point in any contactor. The full form of NO is Normally Open and the full form of NC is Normally Close. This means that when a contractor is off, his NO point will remain normal open and supply will continue to pass through it. Similarly, the NC point will remain normally closed. And he will not pass further supply. 


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