Contactors and Control relays are electrically operated switches used for switching of loads and for controlling the electrical circuit respectively. Generally the medium of quenching of arc is air, so they are called air break contactors & air break control relays. Since both he switches are used in same control panel, so it is confusing for the people to understand the difference between a contactor and control relay.
So what’s similarity between a Contactor and a Control Relay?
Contactor and Control Relay work on same principle. They are basically electrically operated solenoid switches that are designed for the switching or control the loads. Moreover, both of them are constructed in a similar way:
- Both, contactor and control relay, have a top housing which have set of normally open or normally closed contacts. The bottom housing in both cases, have a set of magnet and coil with external cover to protect all the internal parts.
What’s the difference between a Contactor and a Control Relay?
The key difference between control relays and contactors is the rating of current that they are designed to handle. Contactors are used for loads that have comparatively higher currents and higher system voltages.
Here’s a brief definition of Contactor & Control Relay that will help you understand the key difference between the two:
Control Relay: It is a device through which contacts in one circuit are operated by an alteration in conditions in the same circuit or in associated circuits.
Contactor: It is a device which is used for repeatedly establishing and interrupting an electric circuit under normal conditions.
Below table illustrates four major differences between a Contactor and a Relay:
| Criteria | Control Relay | Contactor | |
|---|---|---|---|
| 1 | Size of the Device | Control Relays are comparatively smaller or same in size (upto contactor rating of 12A) | Contactors are larger in size when compared to Control relays |
| 2 | Current Switching Capacity | Control Relays are generally classified as carrying loads of 10A or less | A Contactor would be used for loads greater than 10A |
| 3 | Application | Control Relay is more commonly used in control circuits which are single phase circuits. | Contactors are typically built for switching 3-phase load. |
| 4 | Auxiliary Contacts | A Control Relay consists of at least two NO/NC contacts | A Contactor consists of a minimum one set of three phase power contacts and in some cases additional in built auxiliary contacts are also provided. |
| 5 | Open/Closed Contact Standards | Control Relays can and often are both Normally Open and/or Normally Closed depending on the desired function. | Contactors, on the other hand, are almost exclusively designed to operate with normally open (Form A) contacts. |
| 6 | System Voltage | Control Relays are usually rated to only 250V | Contactors are commonly rated for up to 1000V |
Below are some other criteria that really differentiate the two devices:
Safety Features
- Spring-Loaded Contacts: Contactors are designed to carry high current, and hence contain additional safety features like spring-loaded contacts to ensure that the circuit is broken when de-energized – preventing the circuit from being energized when it is supposed to be off, spring loaded contacts also prevents the contact bouncing which result in long life of contacts. Since Control relays are designed for lower power, spring-loaded contacts are not so common.
- Arc Suppression: Due to the high loads contactors typically carry, they consist of arc suppression to quench the arc faster. As Control relays aren’t designed for high loads, arc suppression is not common on Control relays.
Choosing Between Contactors and Control Relays for Application
When selecting between a contactor and a Control relay; always consider some crucial points.
| When to Use a Control Relay | When to Use a Contactor | |
|---|---|---|
| 1 | 10A or less current | 9A or more current |
| 2 | 1 phase | 1 or 3 phase |
| 3 | Up to 250VAC | Up to 1000VAC |
At C&S Electric, we design and manufacture robust and versatile range of contactors and Control relays that are designed using modern technologies to deliver complete protection and safety with long mechanical and electric life. We offer a range of high reliability Contactors and Control Relays including RobusTa Contactors & Overload Control Relays, Mini Contactor, D-Range Contactors, 2 Pole & 4 Pole Contactors, exceeD Contactors, Robusta2 Contactors, Capacitor Duty Contactors and Definite Purpose Contactors.
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Credit- C&S Electric. Published by Department of EEE, ADBU: tinyurl.com/eee-adbu
