Relay and contactor are both virtual devices in electrical systems. Relay and contactor are used in the electrical system according to the requirement of the electrical system. If the requirement of the system is one relay, then it could not use more than one relay in the system. You can not use a contractor in this system instead of a relay. This article discusses relay vs. contactors. What are these two components, what are the construction and functions, and what are the applications of these two components?

So let’s get started to explore more about relays and contactors.


You use a lot of switches in your home, office, and other places. Like these switches, the relay is also similar to a switch. The difference between relay and switches is just the way of switching. In real life, we use our fingers to operate the switch, while in an electronic relay, the switch operates electromagnetically. The purpose of relays is to make or break electronic circuit connections. There are two stages of the relay:

  • Open
  • Close

A relay without a closed contact (NO) is not energized. In contrast, if the relay is closed (NC), it is not energized as it has a closed contact. The energy supply (electricity or charge) tends to change the states.             

Relay function

Electronic and electromechanical relays operate by opening and closing circuits. Relays open and close the contacts of another circuit to control another circuit. An open contact is created when a relay is not energized when its contact is usually open (NO). Relays are unenergized when their contacts are closed. The electrical current will affect whether the contacts are closed or open.

Small motors and Solenoids usually draw low amps when relays control them, so they are not typically utilized for power-consuming devices. Relays can switch larger voltages and amperes even with a small voltage applied to their coil because a small voltage can cause a significant voltage to be applied to the contacts.

Following are the name of some faults that can happen with any electrical system:

  • Overcurrent
  • Undercurrent
  • Overloads
  • Reverse currents
  • Protective relays

The abovementioned faults are very dangerous for any electrical system; with the use of relays, you can protect the system. In addition, relays are commonly used to turn on starting coils, heating elements, pilot lights, and alarms.

Relay types

Relays can be classified according to their properties into various types and categories. Each of these types of relay has a specific application.

  • Electronic Mechanical Relay (EMR)
  • SSR (Solid State Relay)
  • Hybrid Relay
  • Reed Relay
  • Electrothermal Relay (Thermal Relay)
  • Polarized & Non-polarized Relay

Relay application

There are many applications for electromechanical relays. Various types of relays are available for multiple applications, based on various factors such as the rating of the contacts, the number and type of contacts, the voltage rating of the contacts, operating lifetime, coil voltage and current, and package. Relays are often used for controlling, automating, and protecting power system networks.

The typical applications of electromagnetic relays are motor control, automotive applications like an electrical fuel pump, industrial applications such as controlling high voltages and currents, controlling large loads, etc.

Read More: All Important Information That You Must Know About What Is An Control Panels In Electrical?


A contactor is a device that switches an electrical circuit with the help of electricity. By using a circuit whose power is much lower than that of the motor switch, an electromagnet may be able to operate 230-volt motor switches.

Contactor Functioning

Electromagnetic fields are excited by currents that pass through the contactor. An excitable electromagnet creates an electromagnetic field in the contactor core that moves the armature. A normally closed contact (NC) completes the fixed and moving contact circuits. Bypassing the current through the contact, the current reaches the load. After the current is removed from the coil, the circuit is opened, and the coil becomes de-energized. Contactors are known for opening and closing their contacts rapidly.

Contactors type

  • Magnetic Contactor
  • Manual Contactor
  • Manual Contactor
  • AC contactors
  • DC contactors
  • Three pole contactors
  • Four pole contactors

Contactors applications

  • Contactors are used to start and stop induction motors using Star-delta and Forward-reverse starters. Contactors are also used to start and stop heating loads.
  • They are used to switch a capacitor on and off.
  • You can control multiple lights with the help of contractors.

Contactors vs. Relays

A contactor and a relay are very different devices. Some of these differences are described below:

Auxiliary Contacts

Auxiliary contacts in contactors can be confusing because they can be either NO or NC. Still, the purpose is to perform additional functions related to the contactor control. A contactor can transmit motor power. The control circuit of the motor starter can also be connected with an auxiliary contact, which would light up a pilot light to indicate that the motor is running.

 Capacity and Power

Second, both relays and contactors have different capacities for handling load. Electrical relays are typically used with loads up to 10 amps, while contactors are rated for loads exceeding ten amps.


To help you compare the two, you can follow a few general rules.

  • Here are some tips for choosing relays.
    • Use current less than 10A.
    • Use 250VAC or DC for the coil voltage.
  • The following situations require a contractor:                     
  • Currents of 9A or more
  • Up to 1000VAC
  • 1 or 3 phase

Relays are used to regulate the contacts in an electrical circuit when one or more of the circuit’s characteristics or circumstances change. Contrarily, contactors are employed frequently under various circumstances to interrupt or make connections in an electrical circuit.

A contactor is a kind of relay.

A contactor is a unique kind of relay used to turn on or off an electrical circuit. They are most frequently utilized in lighting and electric motor applications.


Hopefully, now that you understand relay vs. contactor, you’ll have an easier time deciding. Next time, while working on an electrical system that requires either relay or contactor, you can choose accordingly after reading this article. It is recommended if you are working on high voltages than working under the supervision of a professional.


  • What are relays and contactors used for?

Signal detection, transmission, conversion, or disposal are the main functions of a relay. It is usually used to control weak signals in control circuits because of its small on-off circuit current. Typically, a contactor connects or disconnects the primary circuit.

  • How do relays and contractors differ?

Relays operate to allow us to change contacts in a circuit continually. The alteration is accomplished by altering a single circuit or two related circuits. On the other hand, an electrical contractor consistently interrupts and creates electrical circuits in a typical setting.