What is Contactor: Definition and 16 Discussions

In semiconductor testing, contactors can also be referred to as the specialized socket that connects the device under test.
In process industries, a contactor is a vessel where two streams interact, for example, air and liquid. See Gas-liquid contactor.A contactor is an electrically-controlled switch used for switching an electrical power circuit. A contactor is typically controlled by a circuit which has a much lower power level than the switched circuit, such as a 24-volt coil electromagnet controlling a 230-volt motor switch.
Unlike general-purpose relays, contactors are designed to be directly connected to high-current load devices. Relays tend to be of lower capacity and are usually designed for both normally closed and normally open applications. Devices switching more than 15 amperes or in circuits rated more than a few kilowatts are usually called contactors. Apart from optional auxiliary low-current contacts, contactors are almost exclusively fitted with normally open ("form A") contacts. Unlike relays, contactors are designed with features to control and suppress the arc produced when interrupting heavy motor currents.
Contactors come in many forms with varying capacities and features. Unlike a circuit breaker, a contactor is not intended to interrupt a short circuit current. Contactors range from those having a breaking current of several amperes to thousands of amperes and 24 V DC to many kilovolts. The physical size of contactors ranges from a device small enough to pick up with one hand, to large devices approximately a meter (yard) on a side.
Contactors are used to control electric motors, lighting, heating, capacitor banks, thermal evaporators, and other electrical loads.

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  1. srinaath

    Current rating for an electromechanical contactor

    I have a elctromechanical contactor (contactor is an electrically operated switch - It is larger version of relay) which has following specification, Inductive full load current - 30A Resistive full load current - 40A Why is rated inductive current less than rated resistive current?
  2. srinaath

    Definite purpose and general purpose contactors

    I came across a contactor catalog saying "Definite purpose". Then tried to figure out the types of contactor. Came across definite purpose and general purpose. What is meant by definite purpose contactor and general purpose contactor? On what basis can i choose definite purpose?
  3. Nikhil N

    How to wire the contactor just to switch on and off

    I am first time using a contactor. I have a 3-phase contactor with me, Need to switch on and off without any load connected. It has two auxiliary terminals A1 and A2, for just to turn on how it should be connected?
  4. Nikhil N

    How to make 3-phase contactor to chatter?

    I have a ABB A16, 3 phase contactor. I need to generate burst signals from this contactor as similar in relays when it switching on and off frequently. I need the circuit diagram for making the contactor to chatter. The circuit I used to make chattering relay was as below:
  5. R

    Electromagnets and contactor relays

    I am supposed to make an electromagnet for a project. how will i know what gauge of wire to use and how many turns do i need so that my electromagnet will only get 100mA of current from a 24V dc source? Thank you!
  6. S

    Can Two Control Signals Be Safely Connected to a Single Phase Contactor Coil?

    If I have a contactor that I want to use with two separate control sources, on a site with a single phase power source, is it possible to connect two 120V control signals to the contactor coil, potentially live at the same time and connected to the same source, without causing a short, or...
  7. W

    Development of a contactor, prototype manufacturing

    I am designing a contactor for both DC and AC mainly for polarity independent circuit-breaker. It has a contactor unit, actuating solenoid, arc chute, Electromagnetic arc blow out coil Auxiliary contacts and base plate. Basically i got stuck in the Time constant measurement, ie the Bracking and...
  8. L

    Is a Contactor Suitable for High Power 3 Phase Transfer Switching?

    I am designing a transfer switch to switch main power to Generator when main power is lost. Main power is 3 phase, 480VAC and rated at 300amps. Is a contactor a good choice for this? I cannot seem to find one rated this high of power.
  9. N

    Power electronic switches VS dc contactor

    As we know the contactor in power circuit make spark when it open and so its contacts may damage and aging Is it possible to replaace the contactor by power electronics switches such as MOSFET TRIAC and IGBT? Any help will be appreciated
  10. E

    My IEC Contactor Coil keeps overheating

    I have a 3ph IEC contactor with 120v coil voltage. For some reason, the coil starts heating up like crazy when I run it. I have 121v on L1, 120v on L2 and 121v on L3. I re-connected all the wiring to make sure there were no loose connections but still it keeps heating up when I energize the...
  11. J

    Two Phase Power For Contactor Coil?

    Is anyone able to explain why someone wired this motor contactor circuit such that activating the coil is done by connecting the two leads to the following: contactor: Allen-Bradley 69A86 lead 1: 120V AC lead 2: 120V AC - Phase Shifted by 120 degrees So I guess the difference of the...
  12. I

    Contactor with auxillary contacts

    Hi, i want to make automatic on/off the 3 phase pump with float switch and 3 phase contactor(with auxillary contacts) for my tank. i have, 1. contactor with auxillary contacts(3 phase contactor , a1,a2 coil voltage 220volts, no and nc) 2. Float switch(single phase) 3. with this i want...
  13. I

    Contactor with auxillary contact

    Hi, i want to make automatic on/off the pump with float switch for my tank with contactor(with auxillary contact) i have, 1. contactor with auxillary contacts 2. Float switch 3. Manual On/Off switch for pump i want the connection details according to attached diagram. Thanks.
  14. A

    Wiring Diagram for 3-Phase Contactor with Two Switches - Ahmed Hassan

    Hi everybody I am new here but I hope that you help me. I need wiring diagram for 3-phase contactor with two switches one for start (give the contactor the signal) and the other for stop. when the electricity went off , the contactor should stop working it's too simple not...
  15. M

    Magetic contactor humming noise

    Hello. The ac contactor with two magnets sometimes give a noise.For some contactors humming is more audible.What are the possible causes of humming. Also what is the effect of humming on performance of contactor.Can anybody help on this subject?
  16. S

    Contactor vs Relay: What's the Difference?

    I don't see the difference between a contactor and a relay. Can anybody tell me what the difference is, when to use a relay over a contactor ? What are some criterias that need to be taken into consideration when choosing a contactor ? Thanks, Thanks,