Contactors are a critical part of the electrical circuit that is used to secure and break power supply lines passing through the electricity line. They are also responsible for establishing or interrupting electrical power circuits. The contactors can perform on their own as a part of a starter or power control device. They are mainly used to control light load and complex machines.
Similarly, contactors are also used in motors, heaters, and transformers, and is considered as a converging point between a power circuit and a control circuit. Since the control circuit controls it, it also regulates the circuit between power and loads.
Let us understand the importance of a contactor and its working principle.
What is Contactor?
Contactors are electrically controlled switching devices that are used for electrical switching circuits. Principally, its basic operation is similar to that of a relay up to 12500A. While they are incapable of overload protection and short circuit, they can break the connection when the coil electrifies.
Parts Of A Contactors
The contactors are made of two iron cores out of which one is fixed, and the other one is a movable insulated copper coil positioned on a fixed core. There are six primary contacts for power connection where three are fixed cores, and the remaining are movable cores. All these contacts are made from pure copper.
The contact points, however, are made from a special alloy that is capable of withstanding high current as well as temperature. The primary contacts are responsible for cutting the light control loads on and off, such as relays, timers, contactor coils, etc., that are linked to the contact mechanism.
It has three main parts:
- Coil: It is responsible for providing a force that is required to close the contact. The coil is called as an electromagnet, an enclosure that is used to protect the coil and contactors.
- Enclosure: The main job of an enclosure is to protect the circuit from any dust, oil, or electrical contract. Additionally, it also adds as a protector and an insulator. They are made up of various materials such as Bakelite, Nylon 6 etc.
- Contacts: The main job of contacts is to carry the current to multiple parts of the circuit. They are classified into axillary contacts, power contacts, and contact springs. Each of these contacts has its respective functions.
Working Principle of Contactors
An electromagnetic field is created every time current flows where the active coils draw each other. In the beginning, huge amounts of current are attracted by an electromagnetic coil. As a result, the moving contact is propelled by moving core, and the electromagnet can hold the moving and fixed contacts together due to the force created.
Once it de-energizes, the contactors coil spring moves back the electromagnetic coil to its initial position, and the current no longer flows in the circuit. At the same time, if contactors are electrified with AC lines, the magnetic flux of the core experiences a slight delay. Simply put, the working principle of the contactors is to pass current through the contactors, when it electrifies the electromagnet.
As a result, the energized electromagnet creates a magnetic, causing the core of the contactors to move the rotating coil. This is when the circuit is complete between the fixed and moving contacts by a closed contact that allows the current to move from the contacts to the load. When the current stops flowing through, it de-energizes the coil and opens the circuit.
The contactors are able to rapidly open and close, which makes them capable of handling larger loads. They are also constructed and designed to enable the contractors to rapidly open and close. As a result, the moving contacts may recoil rapidly as they collide with fixed contacts. This is the reason bifurcated contacts are preferably used in many contactors to prevent bouncing.
The current input to the coil can be either DC or AC. It is essential to note that the contactor coil utilizes up a very small amount of power for its operation. To reduce the amount of power drained by the contactor’s coil between the operation, economizer circuits can be utilized.
Remember to consult with a certified electrical professional to get the best recommendations on contactors as they are equipped with the right knowledge to help you find suitable contactors.