Contactors and relays are often used interchangeably but in fact that they are two very different things. They are both switches that are electrically operated to control and switch over loads. Technically, the basic principle between the two is the same, but the core difference lies in their applications. In this article, we will clearly understand the difference between contactor and relay.

Similarities Between Contactors And Relays

Contactors and relays are constructed in a similar fashion, in the send that they have an external envelope to protect their internal components from the outside environment. They both come with an electromagnetic coil which is electrified to open and close the contacts. 

Due to their similarities, there is a lot of confusion in the industry about contactors and relays. As per their definition, the contactor is a device designed to establish and disrupt the electrical circuit under normal conditions. On the other hand, Relay is a device that helps contacts in one circuit operate through an alteration in conditions of the same circuit in one or more related circuits. 

Difference Between Contactors And Relays

Let us now talk about the main differences between the two: 

  • Load capacity: While relays carry loads of less than 10A, a contactor is used when the loads are greater than 10A.
  • Standards for Open/Closed contact: Contactors are specifically designed to operate with normally open contacts. On the other hand, relays can handle both normally open and normally closed, depending upon the function. It means that when a contactor is de-energized, there is no connection. However, with a relay, the connection may still be there.
  • Auxiliary contacts: Contactors are sometimes fitted with auxiliary contacts that can be normally open or normally closed. However, they are meant to perform additional functions associated with the control of the contactor. 
  • Additional Safety features: Since contactors carry high loads, they often come equipped with spring-loaded contacts that offer an additional security layer to make sure that the circuit is broken when de-energized. This is crucial, especially in high load situations, where the contacts can weld together. 

As a result, it can lead to the circuit being energized when, in fact, it should be off. Spring-loaded contacts reduce this possibility by ensuring that all circuits are broken simultaneously. Since relays are normally used in low power situations, spring-loaded contacts are not that common. 

  • Arc suppression: This is another standard safety feature in contactors due to the high load they carry. Magnetic arc suppression extends the path on which that arc would have to travel. If this distance is more what the energy can overcome, then the arc is suppressed. Arc suppression rarely happens in relays because they are designed for high loads, and arcing isn’t much of a concern. 
  • Overloads: Contactors are usually connected to overloads that break the circuit if the current exceeds a certain period of time, normally between 10-30 seconds. This helps protect the contactor equipment from damage due to current. Overloads are uncommon in relays. 
  • Applications: Contactors are mainly built to be used in 3-phase applications, whereas a relay is more commonly used in a single phase. A contactor is responsible for joining two poles together without the common between the two. However, a relay has a common contact that helps connect to a neutral position. 

Since contactors and relays are similar and dissimilar simultaneously, it is essential to take help from an expert service provider to ensure that you choose the right one between the two. Also, licensed professionals know the standard industry regulations, which ensure installation safety!