Before understanding the contactor self-locking wiring, we must first understand the principle of the contactor, as well as the normally open and normally closed contact.
Now let's first explain the principle and structure of the contactor. 380 volt AC contactor has three main contacts, that is, power input line and load terminal outlet line, the input line is three-phase live line L1 L2 and L3, the load terminal outlet line is T 1 T 2 and T 3, the contactor main contact inlet line and outlet line correspond one by one. Respectively,L 1 corresponds to T 1,L 2 corresponds to T 2,L 3 corresponds to T 3, and the main contact is normally open when the contactor is not drawn.
What is normally open? Normally open means that the contact is disconnected, not connected, normally closed means that the contact is connected. The contactor also has a normally open auxiliary contact, that is, the fourth contactor contact on the right side, and the upper and lower contactor are also one-to-one corresponding, the contactor does not draw has always been normally open, the role of the auxiliary contact is the auxiliary button to control the contactor, and the role of the main contact is to control the load end, so it is divided into the main contact and the auxiliary contact.
So how can the contactor pull into operation? If you want the contactor to pull on, the contactor will pull on only if the contactor coil is powered on, the AC contactor coil voltage has 220 volts and 380 volts, the two contacts of the coil voltage connection are A 1 and A 2, that is to say, the coil A 1 and A 2 as long as there is electricity, the formation of 220 volts or 380 volts contactor will pull on, which should be well understood.
The position of the coil is in the middle of the rear of the contactor, and its function is that the coil generates electromagnetic after being powered on, and there is a piece of armature in the middle of the front of the contactor. After the contactor coil generates electromagnetic, it begins to absorb the front armature, and the armature pushes the upper and lower contacts of the contactor main contact and auxiliary contact, so the normally open contact of the contactor becomes normally closed contact. Normally closed contact will change to normally open contact. And we use contactor self-locking main contact contacts and auxiliary contact contacts are normally open contacts, so after the contactor suction contacts are turned into normally closed contacts, that is, the four contacts above the contactor and the four contacts below the contactor are connected, after the connection, the load end of the contactor will have electricity, the load end starts to run, the coil power does not produce electromagnetic, so it will not absorb the armature. And there is a spring in the middle of the coil and armature, which will automatically pop the coil and armature back to the original position, so the contactor normally closed state and return to the original normally open state, the contacts above and below the contactor are disconnected, and the load stops running, which is the principle of the contactor, should be understood! Below we understand the button, the button has a group of normally open and a group of normally closed, stop button we want to connect the normally closed contact, start button we want to connect the normally open contact, the button is pressed normally open into normally closed, normally closed into normally open, the button is released normally open and normally closed and returned to the original position, this is very easy to understand!
Contactor self-locking circuit diagram there are many components, such as thermal relays, fuses, indicators and so on.
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The 380 volt contactor self-locking main contact connection is connected to three three-phase power supply above, the load terminal below, coil A 1 and contactor L-1 connected, that is, coil A 1 long charged, we control the contactor by controlling the contactor coil A 2 power supply, power supply L 3 through the circuit breaker or fuse to the stop button, stop button we need to connect the normally closed contact. That is, it is always connected, and then the power goes to the normally open point of the start button, the normally open point of the start button comes out to the contactor auxiliary contact, and the contactor coil A 2 is connected as shown in the figure. Then the normally open line of the start button is divided into a line under the contactor auxiliary contact, this line is very important, because the stop button we connect is normally closed, and if we do not press it, it is always connected. So the auxiliary contact is constantly charged below.
We press the start button, the start button is normally open to normally closed, so the power supply through the auxiliary contact to the coil A 2, then the coil A 1 and A 2 form 380 volts power supply, so the contactor begins to pull, the contactor upper and lower contacts are connected, the motor starts to run, but we release the start button, the start button will become normally open, and the power will be off. The contactor can not operate normally, then the contact under the contactor auxiliary contact long charged will come into play.
When we press the start button, the contactor has already drawn, and the auxiliary contact has also drawn, so the power supply under the auxiliary contact also starts to send power to coil A2, so the start button is released, and the power is still being sent under the auxiliary contact, so the contactor forms A self-locking, and we press the stop button, the power is off, and the contactor is disconnected. Therefore, the power supply under the auxiliary contact does not work, which is the principle of contactor self-locking