What is the contactor, how it works, and its components
What is the contactor, how it works, and its components
In the field of electrical engineering and industrial automation, contactors are considered one of the main devices that play a vital role in controlling and operating electrical circuits. A contactoris known as an electrical control device used to open and close electrical circuits, and is characterized by its ability to control the operation or stopping of electrical devices in an effective manner.
Contactor components:
- Electromagnetic coil:The electromagnetic coil is an essential part of the contactor installation. This coil is connected to the power source, and when activated, it creates a magnetic field that moves the electric arm of the contactor.
- The electrical switch: The contactor is characterized by the presence of an electrical switch that disconnects or connects the electrical current. When the electric lever is moved, the switch is opened or closed to allow or prevent the flow of electrical current.
- Control unit: The control unit is an important part of the contactor, as it allows on and off parameters to be set and defined based on the specific needs of the electrical application.
How the contactor works:
When the electromagnetic coil is connected to the power source, a strong magnetic field is generated that attracts the electric arm and opens the electric switch. The contactor is thus able to disconnect the electrical circuit and prevent the flow of current. When the power is disconnected, the electrical appliances connected to the circuit are turned off.
Conversely, when the electromagnetic coil is disconnected from the power supply, the magnetic field retracts and allows the electric arm to close again, making the switch contact current and current returns to flow in the circuit.
In short, the contactor is an essential device in the world of electrical control, as it contributes to turning on and off electrical circuits in a safe and efficient manner.
InstallationThe contactor includes several basic components that work in harmony to achieve the required electrical control. The contactor consists of two iron cores, which are an essential part that plays a vital role in the control process. These two cores are made of silicon wrought iron metal strips, to reduce eddy currents that cause overheating and energy loss. One core is fixed, while the other is mobile.
The composition of the contactor also includes other components that play an important role:
- Fixed iron core: This core is shaped like the letter E and is surrounded by an insulated wire wrapped around a spool of insulating material, such as plastic. This coil, known as a coil (COIL), has a specific number of turns and a specific thickness of wire, depending on the voltage it operates on.
- Moving iron core:This core carries several main and auxiliary contact points, and is moved by the magnetic effect resulting from the coil current.
- The coil (COIL): consists of a copper wire insulated with varnish and wrapped around a plastic or fiber spool. When a certain voltage is applied to its terminals, a magnetic field is generated.
- Touch points:
- Main contact points: They are used to connect or disconnect the power circuit. They are stronger and can withstand higher currents.
- Auxiliary contacts: They are used in the control circuit and are smaller in size and carry lower currents. It can be open or closed.
How the contactor works:
When the coil is operated by the control circuit, a magnetic field is generated that attracts the moving core towards the stationary core. The position of the contact points changes, with closed points opening and open points closing. This remains the case until the current is disconnected from the coil, when the moving core returns to its original position under the action of the spring mechanical lever, and the contacts also return to their original position.
How to know and identify contactor parties:
Before connecting the contactor, the main and auxiliary contact points and the two terminals of the tube must be determined. In some contactors, the main and auxiliary contacts are placed in one level, while the auxiliary contacts on the sides are in another, making them easier to identify.
Identifying the contact points in the contactor is a vital step to ensure that they are connected correctly and achieve the desired functionality. Key points can be easily identified using consecutive numbering or designations such as (1-2-3-4-5-6) or (T3-T2-T1-L3-L2-L1). As for auxiliary contact points, open (NO) points are always designated in the tens place with numbers such as 3 and 4, as are points 13-14. Closed points (NC) are always under numbers 1 and 2, as in point 21-22.
As for the contactor coil, it is connected through points A1 – A2 and is present in all types. The two ends of the coil (the tube) may sometimes be adjacent to each other or located in two different directions, depending on the type of contactor.
To determine the contact points more accurately, measuring devices such as an ohmmeter or amphometer can be used. When using an analogue ohmmeter, its two ends are placed on the points to be checked, and if the pointer moves when the contactor is pressed and returns to its place, this indicates that this point is open. If the cursor does not move, the point is closed.
Using the ohmmeter, the ohm mode is selected and its two ends are placed on the point to be examined. If the reading O.L. If the contactor is free, and when pressed, the ohm is 0, this means that this point is open (N.O), and vice versa, it means that it is closed (N.C).
Finally, the contact points must be confirmed using the device’s data sheet or contactor, or using appropriate measuring devices.
When selecting a contactor, many factors must be considered to ensure its effective and reliable performance. Here are some points to consider:
- Motor current intensity:
- The current or power of the motor that the contactor will control must be known. This helps in choosing a contactor that matches the loading strength.
- voltage difference:
- You must know the voltage at which the control circuit connected to the contactor operates. The coil voltage must match the circuit voltage.
- Number of contact points:
- The number of open and closed auxiliary contacts required to suit the requirements of the control circuit must be known.
- Operating voltage of electromagnetic switch coil:
- The ability of the electromagnetic switch coil to operate at different voltages, whether continuous or alternating, must be verified.
- Load current intensity:
- The load current intensity or its power in horsepower or kilowatts must be taken into account to determine the capacity of the main contacts.
- Contactor uses:
- You must know the scope of use of the contactor and ensure that it suits the type of application intended, whether it is to run motors or control other power loads.
By choosing the appropriate contactor according to these points, the stable and safe performance of the electrical system can be ensured, and effective control of electrical equipment can be achieved.
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