What is a Contactor and How Does it Work?

Contactors are heavy-duty electromagnetic switches that are normally used in controlling large lighting loads and motors. They operate similar to relays, but often times deal with more voltage, higher amperage, and have more input and output options.

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CONTACTORS
Contactors are extremely useful pieces of equipment that allow switching of several different circuits at the same time. They are flexible for logic controlling as well, so you can use many contactors for turning things off WHILE turning other things on at the same time. This is similar to how control relays work, except that with contactors you generally have larger coils, bigger contacts, and can control much larger loads than a typical relay could handle.

THE COIL
A contactor works similar to a light switch, however rather than needing to manually touch the switch to turn it on/off, you send current to the coil inside and that acts as your switch. The inside of the contactor has 2 large iron cores that are spaced apart from one another, with a coil of copper wire wrapped around them. When current is sent to this coil of wire, the iron cores slam together (as an electromagnet is created) and the contacts of the contactor either open or close…or both at the same time depending on which type you have.

#contactors #relays #electrical
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[Huskyresqr]

you left out one of the most important roles of contractors, especially those used in industrial machinery the machine loses power...for any reason....the (non-latching) contractor will prevent the machine from restarting when power around rotating equipment, this can be life

[mefistafree]

i watch you to learn English i am an electrician and this channel really helpful to improve listening skill and increase vocabulary memory when i hear a vocabulary or idiom that i never heard before i can guess what do you mean because you are talking about my job


when i was an apprentice i was in trouble with contactors and relays

[jesperlowinger]

Hi im 23 y old from sweden.
Currently im rebuilding a mig welder, everything except the transformer is getting replaced.
Now i need to control gasvalve, Wire feed speed and transformer with the mig torch as the main switch.
I have a plan, but i just want to give you props for your work. Always good clean easy to understand information and no BS. Keep it up!
Cheers from sweden / Jesper

[goaliedude]

My favorite use for contactors so far were in an autobody shop that had 12 garage doors all on automatic door openers. When the technicians (or anyone) drives up to the garage door, the door sensor opens the door and they drive in without getting in/out of the vehicle.

At the end of the day when they close up shop, the shop light switch also feeds to a contactor that interrupts the garage door circuits. When the lights are off none of the garage doors will open at all. There is no power going to them, cut off by the contactor.

It's not really that complicated, but I thought it was a very clever solution on how to lock 12 garage doors easily with the least amount of effort

[morisn]

Very down-to-earth explanation, dude. I like it. I actually studied electricity in high school at a time when computers were a luxury item in schools (not even homes, but schools). So I am reminiscing this knowledge buried in my brain for decades because I need it now. I'm glad I found this video.

[KevinCoop]

Dustin, Well done again! A few comments. Relays 10 amps and below, contactors 20 amps and up. Mechanically held contactors have coil clearing contacts to cut power from the coil once changed. NEMA(USA standard) (black) rated contactors good for 100, 000 operations, IEC(European standard) (white) rated for 10, 000 operations. I hope you do not mind the additional information! I hope electricians aren't really connecting coils without checking the voltage first! Respectfully, Kevin

[halidespecialist]

These vids are a lifesaver. I'm a residential electrician trying to figure out industrial controls at this new job.

[robertoperez]

Hi, I really worked with enough mechanical and non-mechanical contactors. for mechanics and had to use relay to be able to unlach. Today I tried to convert a mechanical one like the one you show in the video so you don't have to use the relay but when it was connected it was not fully connected, it just jumped continuously, I think it is coil separation. I returned it to its normal state and it worked perfectly

[cuper]

Thanks for all the good info. Here is a slightly different way of thinking about the same things you've said. Spoiler alert, point 4) is the real differentiator between a relay and a contactor.

1) Both relays and contractors are passive power amplifying switches. On a relay, the control currents are typically measured in milliamps and the voltages are typically < 24 volts. The output currents are measured in amps and the voltages are < 240 volts. On a contactor, the control currents are typically measured in 100s of milliamps and the voltages are typically < 120 volts. The output currents are measured in 10s or 100s of amps at voltages of 120 to 600 volts.

2) Both relays and contractors can be used identically in logic situations to implement boolean logic as part of your control system.


3) The main thing that distinguishes a relay from a contactor is how they are made inside. Both relays and contractors have arcing problems (which erodes the points) when the points of the device open and close under load. In a relay, "normal" material and switch design can be used and still provide a life of 10s or 100s of thousands of operations. In a contactor, "special" material and design must be used to provide a reasonable number of operations before the points wear out.

4) A second differentiator between the two is how the internal connections are made. In a SPST relay, there is one set (pair) of contacts and the armature (the part that moves and actually makes contact) is live (i.e., is connected to one of the output terminals). In a SPST contactor, there are two sets (pairs) of contacts and the armature is dead (i.e., is not connected to either output terminal). When a contactor is activated, the armature causes both sets of points to contact and the output current then flows through the armature. But the armature is never directly connected to either output terminal.

5) Point 4) is driven by power design considerations, but also provides a level of safety for high power circuits.

This is how an engineer (at least this engineer) thinks of these things. This electrical engineer also put himself through college working as an electricians assistant and still maintains a high level of respect for master electricians who are dedicated to their craft.

[paprikadesign]

I just started my apprenticeship at a switchboard company and this video (as all the others from you) is extremely helpful. Thanks heaps!

[kelsie]

Thank you so much for this video - this really helped me understand exactly what a contactor is and how it works! Great video and I love that you explain is so simply!

[MicahFunk]

Back in the eighties, when I was learning about this, I was taught to look at the contactor like a knife switch or door. When the knife or door is closed, then, it connects; whenever the knife or door is opened, it disconnects. 🚪🤓

[arthurmoore]

The lighting contactors and conversion kits were new information to me. So, thank you.

[elperro]

Excellent video, really easy to understand, please keep making them.

[brandonharris]

Awesome video you are very good teacher! This info helps tremendously thank you keep up the good work! 👍

[danielliu]

Really clear Demo, love to see the parts take off the contactors.

[IsmaelTerrenoIBunkerteam]

Amazing job ! great video! thanks for the explanation

[CAMMEDcivic]

Had to refresh my mind, thanks again Dustin! 💯

[alvarobarboza]

great content.
good music in the opening and closing segments.
thank you.

[DavidR]

Well you just completely demystified contactors for me, thank you!