Contactor and how to change the coil 220/110/24
Contactor and how to change the coil
Contactor and how to change the coil
Contactor:
It is an electro-mechanical connection and disconnection device
It is controlled by a coil whose terminals are on the contactor (A1, A2).
When current passes through this coil, the contactor closes the main contacts.
He changes the position of the control contacts, so that the closed contacts become open and the open contacts become closed.
With the main contacts closed, the electrical circuit is completed between the supply and the load.
The following figure shows the shape of the contactor.
The following figure shows the contactor symbol in electrical diagrams.
The most important information written on the contactor is:
1- Coil Voltage.
2- Electrode voltage (main contacts)…
3- Current or power of the poles.
4- Operating Clique.
Contactor parts:
1- Electromagnet: It consists of a coil and a magnetic core, and it either operates on direct current
(6,12,24,48,60,80), or works on alternating current (24,50,110,220,380).
2- Poles (main contacts): inputs (L1, L2, L3), outputs (T1, T2, T3).
3- Auxiliary contacts: They are either open contacts (N.O.), or closed contacts (N.C) with a time delay that open and close after a period of time is placed.
Operation code:
AC1: For ohmic circuits (P.F=1) such as heating and lighting operations, i.e. we do not have XL or XC.
AC2: Related to wound circuit motors.
AC’2: Related to wound-circuit motors.
AC3: Related to squirrel cage motors.
AC4: Designed for frequent disconnection and connection within a short time.
The contactor is available with a power scale (KW) with the following standard values:
( 4, 5.5, 7.5, 11, 15, 22, 30, 37, 45, 55, 75, 110 )
How to know and determine the edges of the contactor?!
Before connecting to the contactor, you must first determine the main contact points, the closed and open auxiliary contact points, as well as the two ends of the coil.
For main contacts, three points are usually in the open position
(normally open) and take the numbers 1,3,5 as the input (as these inputs to the contactor are the outputs of the electrical circuit breaker) and 2,4,6 as the output.
As for auxiliary contacts, there are some that are in a normal open position
(normally open) and abbreviated with the letters (N.O), and some of them are in a normally closed position (normally closed) and abbreviated with the letters (N.C)
As for the numbers, the open auxiliary points take the numbers (14-13) or the following numbers that start with the number 3, such as (23-24), (33-34)… and so on..
The closed auxiliary points take the numbers (11-12) or the following numbers that start with the number 1, such as (21-22), (31-32)… and so on..
It is possible to determine whether the point is open or closed using a series lamp or multimeter
Where any contact point outside the circuit is tested, that is, the parties connected to it are separated.
If the multimeter pointer does not move on Analog devices or the letter OL appears on Digital devices,
Press the manual button to make the contactor, the indicator will move or give 00. This means that these points are open in the normal position (N.O).
When the hand is removed from the button, the contacts will return to their normal position, and vice versa in the case of closed points (N.C), where the multimeter pointer will move or give 00.
When you press the contactor button, the state will change, and when you remove the hand from it, the contacts will return to their normal position.
comments :
1- Some contactors carry a certain number of auxiliary contact points, and no other points can be added.
As it is found in many brands, the contactor has one auxiliary contact point and a piece can be installed on it that carries a number of additional auxiliary points.
It becomes an integral part of the contactor, moving by the force of the magnetic field of the same coil.
It is possible for a single point or piece to contain two or more open and closed points.
2- This same idea is used to place a mechanical timer on the contactor.
For the ends of the coil:
The coil usually has two terminals, designated A1-A2 or A-B. When measured with a multimeter, it will give a certain resistance value, not zero, and this is very important in maintenance.
Contactors have coils that operate at different voltage values, including 24, 48, 110, 220, and 380 volts. The higher the coil operates at a voltage, the greater its resistance value
It is wound with a thinner wire diameter and more turns. R=
It is possible for the same contactor to operate with a 24 volt or 380 volt coil, and the coil may be changed individually.
The contactor is left as it is, and therefore the value of the voltage at which the coil operates is written on it itself, and not on the body of the contactor, and the number appears on the outer surface of the contactor.
There are many types and sizes of contactors,
When buying or changing a contactor, you must know three basic things:
1- The intensity of the current or capacity of the load that will operate through this contactor.
2- The voltage at which the control circuit operates
3- Number of open and closed auxiliary contact points.
The intensity of the current or capacity of the load that will work with this contactor.
You must first know that the part that bears the intensity of the motor current inside the contactor is the three main contacts
These points are responsible for delivering current to the motor
Therefore, its size and the type of material from which it is manufactured must be able to withstand the current consumed by the load, whatever its type.
Whenever the value of the contactor current is greater than the value of the load current,
It was better and gave the contactor a longer life, but economically, a suitable contactor should be chosen and not much higher.
This depends on the type of load and the number of times it is connected and disconnected, and the brand of contactor must also be taken into consideration
If the number of stop and start times is more, a contactor with a higher value is needed.
The better the brand of contactor, you can choose it with a value close to the value of the load current.
It is known that the same capacity of the motor, whenever it operates at a higher voltage, the intensity of its current decreases, and vice versa
Therefore, you will find a table on the 9 amp contactor that records if the engine is running at 220 volts, so the contactor is suitable for an engine with a capacity of up to 3 HP.
If the engine runs on 380 volts, the same contactor is suitable for an engine with a capacity of up to 5.5 HP.
The voltage at which the control circuit operates (coil voltage).
It is related to the value of the voltage difference in the control circuit. It is not required that the control circuit operate at the same voltage as the source.
Rather, it is preferable for it to operate with a lower voltage difference and powered by an independent circuit breaker.
The control circuit voltage is what will reach the contactor coil, therefore
If the control circuit is 24 volts, the voltage of the contactor coil must be 24 volts, regardless of the voltage of the source with which it will operate.
Engine: This is a very important point during the connection process.
Number of open and closed auxiliary contact points.
Depending on what is required of the control circuit, it is possible for the circuit to be without any auxiliary points.
Or it contains a certain number of open or closed points (that is, depending on the application to be performed through the electrical circuit).
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