Contactors and relays are electrically operated switches used for the control and switching of loads. The difference between them primarily lies in the load current that they can handle, where they are used, and how they are used in a circuit. This article can give you a clear picture of the difference between contactor and relay.
Contactors and relays have similar construction. Both have an external envelope to protect all the internal parts from the external environment. An electromagnetic coil is provided for the opening and closing of contacts. The contacts are opened and closed by exciting this electromagnetic coil.
Operation of Relays and Contactors
A Contactor is used for switching motors, capacitors, lights, etc, that drains very high current. It has at least a single pair of three-phase input and output contacts. It would be normally open. Some contactors come with additional auxiliary contacts that may be either NO or NC. These auxiliary contacts get activated along with the main contacts. Switching is achieved by energization and De-energization of the contactor coils. They are chosen based on the current ratings of the load. Contactors require an additional supply (either AC or DC depending upon the type of contactor we use) for excitation.
A relay consists of at least two contacts and an excitation coil. These contacts may be normally open or normally closed. These contacts are closed or opened by exciting the coil. Relays are used for switching control circuits and cannot be used for power switching with relatively higher ampacity. It can be used for switching small lights, sirens, indication lamps, etc.
The key difference between contactor and relay
Relays are switching devices used to control a circuits, a low power devices or multiplying the number of contacts available.
Contactors are switching devices used to switch on/off heavy electrical loads such as electric motors, power factor correction capacitors, lights, reactors, etc.
Contactor vs relays
|Relays are switching devices used in any control circuit for checking a condition or multiplying the number of contacts available.
|Contactors are switching devices used to control power flow to any load.
|Relatively smaller in size
|Larger when compared to Relays
|Used in circuits with lower ampacity. (Max 20A)
|Used in circuits with low and higher ampacity up to 12500A
|Mainly used in control and automation circuits, protection circuits, and for switching small electronic circuits.
|Used in the switching of motors, capacitors, lights, etc.
|Consists of at least two NO/NC contacts
|Consists of a minimum of one set of three-phase power contacts and in some cases additional auxiliary contacts are also provided.
|Relays do not have an arc suppression system built in.
|Normally, contractors have in-built arc chutes for suppression.
- “Understanding Relays & Wiring Diagrams”. Swe-Check. Swe-Check. Retrieved 16 December 2020.
- “Contactor or Motor Starter – What is the Difference?”. EECOOnline.com
1. Contactor v/s Relays
2. Where are contactors used and where are relays used?
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