Contactors and relays are used for switching on and switching off the loads. The air is the medium of arc quenching after switching off the relay or contactor, and they are also termed as air break contactor or air break relay.
Similarity between Contactor and Relay
Both contactor and relay function on the electromagnetic induction principle. When current flow through the coil of the contactor or relay, magnetic field is generated and the magnetic field exerts force on the actuator which pulls the contacts making NO contacts to close and NC contacts to open. The reverse process takes place when coil supply cut off.
Difference between Contactor and Relay
The main difference between contactor and relay is the current rating of contacts. The contactors are designed for handling large current in comparison to current handling capacity of the relay. The major difference between contactor and relay is as given below.
Size of the Device
The contactor is bigger in size as compared to relay. The size of the contactor is bigger because contactor handles more current than a relay. The relay is used up to 16 amperes current handling.
Current Switching Capacity
The relay is used up to current switching of 16 amperes, while the contactor is used for switching off the large loads.
The relay is more commonly used in single phase control circuit. The contactor is used in 3 phase power circuit.
The relay is rated to 250 volts, whereas the contactor is rated up to 1000 Volts.
The relay has usually 2 NO+ 2NC contacts, up to 6 NO+ 6 NC is also possible. The current rating of all the contacts are equal. The contactor has three or 4 contacts known as power contacts which are designed to carry large current. The contactor has auxiliary contacts of lower current rating used in control circuit.
Spring Loaded Contacts
The relay is used to handle lower current, therefore the relay does not have spring loaded contacts. On the other hand, the contactor handle large current therefore the contacts are designed with spring loaded features. This ensures switching off contactor when coil is de-energized. The spring loaded contacts prevents the contact bouncing as well, and hence the life of the contactor gets enhanced.
Arc Suppression System
Contactor is used to handle large current. The arc is formed when the contactor is switched off. The contactor has arc suppression system which quickly suppress the arc at the instant of switching off. Relay is used to handle lower current hence there is no need of arc suppression