Relays can be described as the switches which primarily function to close and open circuits electronically and, at times, electro mechanically. Relays mainly synchronise the opening and closing of the circuit contacts of an electric circuit. To understand this in a simple language, the dictionary defines a relay as “the action of passing something from one thing to another”. This literal definition can be used to understand this device because the signal collected from one side of the device manages the switching exercise on the other side.

A contactor relay is one special category of relays used to handle a large amount of electrical current through its contacts, unlike most other relays that usually handle low power applications. This kind of relay has several contacts which are mostly open, but this may not be the state always. They discontinue power to the load in the case the coil is de-energised. Contactor relays are widely used in lighting control and electric motors.

Contactor relays are large-sized and are usually used for loads higher than 10A. They are designed for regulating 3 phase load and consist of a minimum of one single set of three-phase power contacts. However, at times they also come with additional in-built auxiliary contacts. Every contactor is designed to function with generally open contacts. Contactors are commonly rated for up to 1000V.

Components Of A Contactor

Following are the three vital components of a contactor:
Electromagnet
A coil or an electromagnet is the most crucial component of a contactor. It provides the force that is needed to close the contacts. The electromagnet is always placed within a protected enclosure.

Enclosure

Contactors always have an enclosure that ensures insulation and protection so that the users cannot come in physical proximity with the contacts. This safety enclosure is constructed from various materials like polycarbonate, polyester, Nylon 6, Bakelite, thermosetting plastic, etc. usually, an open-frame contactor comes with an extra enclosure that safeguards the device from external conditions like bad weather, dust, oil, etc.

Contacts

Another vital component of a contactor relay is the contact. It is that part of the contactor that carries the current. There are different types of contacts, like auxiliary contacts, contact springs, power contacts, etc. Each kind of contact has its role to play.

Operation Principle Of A Contactor Relay

Whenever a current passes through a contactor, the electromagnet gets powered, resulting in the creation of a magnetic field. This pushes the contactor core to mobilise the coil. A closed contact completes the circuit between the static contacts and the moving contacts. This allows the current to travel through the contacts and reach the load. When the current is discontinued, the energy from the coil is drained, and this opens the circuit. The contacts of a contactor relay are notable for their swift opening and closing action.

Schneider Electric India has a vast range of contactor relays that is excellent for industrial usage. The TeSys contactors by Schnieder have multiple contacts that are ideal for electric motors.