Difference Between Relay and Contactor

The terms relay and contactor are often used interchangeably, and this is mainly because their functioning principle is the same. Even though the principles may be the same, there are tons of differences between these two components, and their purpose is different too.

In this article, we’ll discuss the differences between a relay and a contactor.

 

Relay and Contactor: An Overview

Before going deep into their differences, it’s better to know each of these devices better, as it’ll help you understand their characteristics better.

What Is a Relay?

what is relay switch

The relay is an electronic device that’s used for operating the contacts in a circuit through the change in different conditions. These changes can be in the same Circuit or even in a different circuit, but that must be done in a way that affects the primary Circuit.

 

What Is a Contactor?

What is Contactor Switch

The contactor is an electronic device that is used for establishing or interrupting any electric circuit under regular conditions.

 

Differences Between Relay and a Contactor

In this section, we’ll discuss the different factors where the relay and the contactor are different from one another.

Application

The main difference that you need to know between relay and contactor is their application. While relays are mostly used in single-phase circuits such as control circuits, the contactors are mostly used for switching a 3-phase load.

 

Current Switching

A contactor can be used for carrying current loads of more than 10A. However, the relays are usually limited to 10A, if not less.

 

Size

When it comes to the size, the contactors are far bigger than the relays.

 

Auxiliary Contacts

The Auxiliary contacts can be either NO or NC, and these are used for performing additional functions. While the number of auxiliary contacts in relays will be two at least, they will be at least one set of three-phase power contacts in contactors, and the number of auxiliary contacts will vary.

 

Voltage

The common voltage rating of contactors is 1000V. On the other hand, it’s usually 250V only for relays.

 

Opening and Closing of the Contacts

While the contacts are designed to work in both open and closed functions in the case of relays, they will work mostly in the open form in the case of contactors.

 

Safety Features

Contactors are required to carry high current, which is why they come with some extra safety features than the relays. First of all, the contacts are spring-loaded, which allows them to prevent energizing accidentally.

Then again, the contactors also come with arc suppression for quenching the arc faster. However, these safety features aren’t usually found in the relays.

 

Difference between Relay and Contactor: A Comparison Table

Relay

Contactor

Application

 

Single-phase circuits 3-phase circuits
Current Switching

 

Can’t carry more than 10A Can carry more than 10A
Size

 

Small in size Larger in comparison to relays
Auxiliary Contacts

 

Must be two one-phase contacts at least Will be at least one 3-phase contact
Safety Features

 

Doesn’t offer many safety features Offers spring-loaded contacts and arc suppression
Opening and Closing of the Contacts

 

Functions in both open and closed mode Functions mostly in open form
Voltage

 

250V 1000V

 

Which One Should You Use?

There are three things to consider when choosing between relay and contactor. These are:

i. Amount of Electricity Passed

If the electricity passed is higher than 10A, then you need a contactor.

ii. Voltage Load

If the voltage load is 250V or below, then go for a relay. If it’s higher than 250V and around 1000V, then use a contactor.

iii. The phase of the Circuit

For one-phase circuits, use relays, and for three-phase circuits, contactors are more suitable.

 

Final Words

Knowing the difference between relay and contactor is important, as it will help you choose the most suitable component for your work. Choose wisely, or you may end up damaging the components!

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