Contactors and Protection Relays

5 Differences Between Contactors And Protection Relays

In the electrical industry, there is plenty of confusion about the differences between contractors and protection relays. For the uninitiated, relays are utilized to control an electrical circuit’s contacts due to an alteration of conditions or parameters in that circuit or any related circuit. On the other hand, contractors are utilized to establish or interrupt links in an electrical circuit in a repeated manner under various conditions.

Operation of Contactor and Relay

A relay is a kind of electromagnetic switch that operates based on the current alteration in a circuit. If a circuit has an overload, it will trigger the relay’s electromagnetic armature to open or close based on the configuration.

A contactor operates in a similar manner to relay. Its electromagnet is energized by the current passing through it. If the electrical circuit has an overload, the energized electromagnet produces a magnetic field. This makes the contactor’s core to shift the armature to an open stance, and this cuts the power flow to the circuit.

Comparison between Contactors and Relays

Let’s have a look at some common and basic differences between contactors and relays:

  1. Load Capacity

To start, the load capacities of relays and contactors are different. Relays are utilized with electrical loads of around ten or fewer amperes. In comparison, the load capacity of contactors is more than 10 amperes.

  1. Auxiliary Contacts

A contactor uses auxiliary contacts to perform functions that are connected to the contactor’s controlling. Also, a contactor’s auxiliary contacts can be normally closed or open as per needs.

  1. Open/Closed Standards

Relays are built to function in both manners, i.e., in a normally closed and normally open method as per the demands of the function. However, contactors are built to run in a normally open mode. To summarize, when a contractor is triggered, there is no link between the contactor and the circuit. However, a relay can or cannot connect with the circuit when triggered according to the relay’s configuration in the circuit.

  1. Safety Functions

Contactors and relays have different safety features based on each device’s power. Spring-loaded contacts are utilized to make sure the circuit is opened or tripped in the event of any over-circuit occurrence to prevent or reduce damage to electrical gadgets. Relays are utilized in circuits with load capacity smaller than or equal to 10 amperes; therefore, relays commonly don’t have spring load contacts because of their minimal load capacity.

However, contactors carry greater loads as they have a load capacity of more than 10 amperes. Because of the higher loads, contactors use spring-loaded contacts that make sure the circuit gets disconnected when it is de-energized because of an overload happening. In circuits with higher loads, the contactors’ connections are welded together. This can cause a dangerous situation because if there is an overload, the circuit will not open. To remove this risk, spring-loaded contacts are utilized.

  1. Applications of Contactors and Relays

Relays are designed to be utilized in single-phase networks, and they thus have single-phase uses. Contractors are built for use in three-phase networks. Relays are commonly leveraged in managing power loads, industrial applications, motor control, and automotive applications.

There are different types of contractors, and they have numerous applications, including common ones such as lighting control, switching of capacitor banks, and motor starters.

Last Word

We advise you to consult licensed professionals to get recommendations for electrical systems. They can provide you guidance in choosing the right electrical solutions for your company’s requirements.


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