Contactor – Construction, Types, Working, Advantages and Disadvantages

What is a Contactor?

A contactor is an electronic device that is generally used in switching circuits ON and OFF. The electronic contactor forms a subdivision of electromagnetic switches is known as relays.

A relay is electrically operated switching devices which uses electromagnetic coil to normally open or normally close a set of contacts. A contactor is a particular type of relay. In spite of the fact that there is some important difference between contactor and a relay. Contactor is principally design for use in application where a large amount of current needs to be switched. Contact manages to use for higher current convey application than standard relay which do a similar work with having low current switching.

Construction of Contactor

A contactor is a crucial electronics device used to operate the flow of electricity in high-current circuits. It is constructed through a strong frame usually, made of metal or plastic; it houses some key components. At its core is an electromagnetic coil wound through an iron core, which is energized to generates a magnetic field. This field crawl with a mechanical connection that operates one or more pairs of contacts through the contactor. These contacts also made up of materials such as silver for optimal conductivity to open or close the control the circuit. Springs make sure that hard contact closure and stop bouncing during operation.

To manage the electrical arc that can happen when contacts open or close, contactors absorb arc suppression devices such as arc chutes or magnetic blowouts. It is also used to provide auxiliary contacts for signaling or interlocking purposes. Basically, a contactor is used in such situations where loads should be turn ON or OFF rapidly or frequently. The contactor is consisting of normally open (NO) and normally close (NC) switch. The two superior application of a contactor is electric motor starter those that uses auxiliary contacts and connectors for use in electric vehicles and another one application is used in high power lighting control systems.

When a contactor is used as a magnetic starter for an electric motor, it will also provide a range of safety features like power cuts, short circuit protection, overload power etc. However, most of the contactor is designed easily mountable and portable which is highly suitable for industrial application. The principle is like how the latching relay works where the latter is more often used in smaller circuits with reduced loads.

How do Contactor work?

The electromagnetic coil is the key component of a contactor. Depends on how the contactor is mounted and will perform a specific action on a switch contact when it receives power.The contacts in components device which carry power across the circuits being switched. There are various types of contact found in circuits such as springs and power contacts. Each types performs a specific function in transferring voltage and current.

The contactor enclosure is another important device. The enclosure is used to protects user for accidentally touching any conductive part of the circuits. It also provides robust protection against risk like overheating, explosion and environmental hazards. If the contactor is designed as only normally open (NO), exciting the coil with voltage will oust the contacts together, establish the circuits and allows power to flow in the circuit. Most of the contactor is designed in such way that when the coil is de-energized, the contacts will be open and then the circuit will be OFF.

If the contactor is designed as only normally close (NO), these circuit is working opposite way of normally open (NO). The circuit is complete, and contacts is closed while the contactor is de-energized but interrupted contacts open whenever the current is supply to the electromagnetic coil. It is a less common configuration for contactor, and it is relatively common alternative setup for standard relay switches.

Working Principle of Contactor

A contactor operates based on the principle of electromagnetism to handle the flow of electricity in high-current circuits. At its core is an electromagnetic coil that, when energized by a control voltage, which is used to creates a magnetic field. This magnetic field entice a movable armature or backer that is mechanically connected to one or more sets of contacts. As the armature start moving it either closes or opens these contacts. Closing the contacts completes which the circuit, and allows electrical current to flow within the load, whether it’s a motor, heater, or other equipment. Opening the contacts and obstruct the current flow virtually stopping or disconnecting the circuit.

Springs are connected to make sure that proper contact pressure when the contacts close, which is crucial for maintaining a reliable electrical connection and preventing arcing. Contactors contain mechanisms like arc chutes or magnetic blowouts to prevent arcs that may occur when the contacts open, and make sure long-life and safety of the contacts. Overall, contactors play a vital role in industrial and commercial applications where sturdy and logical control of electrical power is necessary, to provide a safe and reliable means to manage high-current circuits.

What are Contactor is used for?

A contactor is used in wide range of situations where there is need of switch power to circuits repeatedly. As like switch are design and build to perform this task over many thousands of cycles. A contactor is mainly chosen for higher power applications than relays. Because of their ability to allow low current and voltage to a switch, power cycle and turn higher current or voltage circuits ON and OFF.

Types of Contactors

a. Magnetic Contactor: A magnetic contactor operates via electromagnetism, and it does not require any direct intervention to perform its function. In contrast, a magnetic contactor operates mainly through the use of an electromagnetic coil to handle the switching of high currents and voltages. When the power supply is applied to the coil, it generates a magnetic field that connects a movable armature or plunger. This mechanical movement whether closes or opens electrical contacts and allows them for interrupting the flow of electricity in the controlled circuit.

Magnetic contactors are crucial in industrial and commercial applications where heavy currents required to be switched on and off accurately and efficiently. Basically, it is used for controlling electric motors, heating systems, lighting circuits, and other equipment which required remote control capability.

b. Switch Ratings and Contact Ratings: Contactor switch ratings is basically given as two different metric that is maximum switching current and maximum switching voltage. The upper limits of current and voltage must be always direct assessed in terms of requirements for the motors or circuits where it is been used.A switch rating contactor is also called as a switch-type contactor, which is designed mainly for switching low currents and voltages manually. It combines the function of a manual switch with that of a contactor and allows for both manual operation by a user and remote operation via an electromagnetic coil.

These contactors usually feature a lever or control manually toggles the contacts open or closed. This design facilitates direct handle over electrical circuits without depend on and simply automated or remote systems can be controlled. Switch rating contactors are basically used in various applications where operators required instant and direct control over circuit operation, such as emergency stop circuits, maintenance switches, or control panels requiring simple on/off functionality. 

Advantages of Contactor

1. Handling High Currents: Contactors is used to control large currents, which make them suitable for controlling heavy-duty electrical loads like motors, heaters, and lighting circuits etc.
2. Arc Suppression: Many contactors provide features such as arc chutes or magnetic blowouts to subdue arcs when contacts open, increase safety and extend contact life.
3. Compact Design: They are available in different sizes and configurations, which make suitable for flexibility in installation and space-saving designs.
4. Longevity: By doing proper maintenance and care, contactors can have a long operational life, and make it cost-effective for long-range duration.

Disadvantages of Contactor

1. Mechanical Wear: In spite of their durability and frequent switching can guide to mechanical wear of contacts and springs, requiring cyclic inspection and replacement.
2. Noise: Contactors can make perceptible noise during operation, usually when switching large currents or due to mechanical vibration.
3. Initial Cost: High-quality contactors can be expensive, usually designed for high-current in industry applications.
4. Heat Generation: When carrying high currents, contactors can generate heat, which may require additional cooling instruments which depends upon the different application.

Also read: Difference between Isolators and Circuit Breaker

Power Supply Failure Alarm Circuit

Conclusion

It is an electrical switch used to control electric motor or other devices. A contactor plays an important role in managing the flow of electricity. It required maintenance regularly, and also required proper selection for optimal performances.

FAQ for Contactor