Difference between contactors and relays

Contactors and relays are two closely related terms. Both of them are electrically controlled switches used for control and switching of loads.

Constructional Features:

Contactors and relays have similar building. Both have an outside envelop to shield all the internal parts from outside surroundings. An electromagnetic coil is provided for opening and closure of contacts. The contacts are opened and shut by exciting this electromagnetic coil.

Difference between electrical contactors and relays

electrical contactorsA Contactor can be used for changing of motors, capacitors, lights etc, that drains really high current. It’s at least one pair of three phase input and output contacts. It’d be generally open. Some contactors comes with added auxiliary contacts which could be either NO or NC. These auxiliary contacts getsactivited together with the primary contacts. Changing is reached by energization and De-energization of the contactor coils. Contactors are selected upon the ampere ratings of the load. Contactors needs yet another supply (either AC or DC dependant on the kind of contactor we use) for excitation. It’s used for electricity changing.

A relay contains 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 changing of control circuits and cannot be used for electricity changing with comparatively higher ampacity. It may be used for changing of little lights, sirens, indicator lamps etc.

To turn things on and off, we want devices which are switchable by the use of a current or voltage. Electrically, we’ve transistors and integrated circuits. Mechanically, we’ve relays and contactors. The primary difference between contactors and relays is the loads they are designed to manage. Contactors are used for loads that have high voltages, high currents, or both. Contactors are used for devices that pass more than 15 amps or batch of more than 3kW. For lower numbers, average relays are used.

When it comes to characteristics, a contactor has some than ties in directly with the preceding difference. A contactor has arc suppression mechanisms while relays usually aren’t. At really high power loads, it is extremely possible that currents will arc across contacts while the switch is in transition. Arcing can cause serious damage to the contact points causing it to fail much earlier than its anticipated life. Arcing is not as likely to happen at lower voltages where relays are commonly used.

Another difference between contactors and relays is the quantity of electricity they use up. Contactors should change bigger contacts, so they also have substantially bigger electromagnets that draw substantial numbers of electricity. In contrast, the smaller electromagnets in relays are easier to change and doesn’t need just as much electricity.

electrical contactors and relaysThe preceding difference is crucial if you think about the circuitry used to determine the substitution is electronic in nature. These circuits will not be with the capacity of supplying the electricity needed to change contactors; on the other hand, can be changed by electronic circuits with comparative ease. As a result of this, relays in many cases are used as a middleman between the electronic circuit and the contactor. The electronic circuit supplies the electricity to turn the relay on, which changes a bigger voltage source needed to turn on a contactor.

Selecting between a relay and a contactor isn’t extremely hard. You should just examine your planned program. For most instances, relays can do the job with no trouble. But for high power applications, using a contactor may be required.

Comparatively smaller in size
Used in circuits with lower ampacity. (Maximum 20A)
Primarily used in control and automation circuits, protection circuits and for changing little electronic circuits.
Consists of at least two NO/NC contacts

Bigger compared to Relays
Used in circuits with low and higher ampacityupto 12500A
Used in the changing of motors, capacitors, lights etc.
Consists of minimal one set of three phase power contacts and in some instances added auxiliary contacts may also be supplied.


A contactor manages considerably higher current flow than relays
A contactor has arc suppression mechanisms while relays aren’t
A contactor draws significantly more electricity than relays
A relays can be used as a middleman between electronic equipment and a contactor


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