What is a Contactor? | Working Principles
ฝัง
- เผยแพร่เมื่อ 7 มิ.ย. 2024
- ▶ C'mon over to realpars.com where you can learn PLC programming faster and easier than you ever thought possible!
=============================
▶ You can read the full post here
realpars.com/contactor
=============================
⌚Timestamps:
00:00 - Intro
00:39 - What is a contactor?
00:55 - Why contactor is used?
02:44 - Contactor vs. relay
03:39 - How to wire a contactor
03:43 - 1) Coil terminals
04:53 - 2) Contacts terminals
05:55 - 3) Auxiliary contact terminals
06:10 - How does a feedback contact work?
07:08 - How to wire a contactor to the PLC and motor
=============================
In this video, we will explain what a contactor is, how they work, how to wire a contactor, and the difference between a contactor and a relay.
A contactor is a device that is for making and breaking an electrical power circuit. For example, we usually use a contactor for turning on and off an electrical motor.
Why do we need to use a contactor? Can't we connect the motor directly to the PLC? Well, the short answer is no. Because you don't want to connect a high voltage electric motor to your shiny expensive PLC directly. This will damage the PLC cards if there are any electric surges on the motor's side.
We use a contactor to connect the PLC to the motor indirectly and safely. All contactors have a low voltage coil. We connect the PLC output to this coil. This coil usually works with a 24-volt DC signal.
Once the coil is energized, an electromagnetic field will be created. This electromagnetic field then causes the contacts to be closed and that's how the 3-phase power will reach the motor and can turn it on. So, there is no electrical connection between the coil and the contacts.
In the normal state and when the coil is not energized, the contacts are open and when a 24-volt DC signal is sent from the PLC, the coil will be energized, the contacts will close and the motor turns on.
A relay works the same way as a contactor. That means a relay also has a coil and some contact. When the coil is energized, the contacts will close.
But here is the difference... a relay is usually used for smaller devices with lower current and voltage rates. A contactor, however, is used for bigger devices with higher current and voltage rates.
Let’s talk about the wire terminals on the contactors.
1) On the front of the contactor, we see two wire terminals of A1 and A2. This is where we can connect a 24-volt DC power to the coil to energize it.
The coil may work with different voltages such as 12-volt DC, 24-volt DC, or maybe 220-volt DC.
Depending on the type of the contactor, the coil can also work with a 24, 120, or 220-volt AC power.
2) On the other side of the contactor, we have six other wire terminals. The wire terminals on the top are labeled from left to right with L1, L2, and L3. The wire terminals on the bottom are labeled from left to right with T1, T2, and T3.
The L1, L2, and L3 terminals are where the power wires connect to the contactor. The T1, T2, and T3 terminals are where the device wires connect to the contactor.
3) We have another set of wire terminals on the front end labeled as NO or normally open. This is a simple normally open contact referred to as an auxiliary contact or a feedback contact.
This contact is used to send a signal to the PLC input about the contactor's health. When the coil is energized and the three main contacts are closed, the feedback contact will be closed as well and send a signal to the PLC input.
We have discussed this more in our level 2 PLC programming course and there is a sample PLC program that shows why we always need to use a feedback contact and how to use that contact in the PLC program to get notified when the contactor is broken: bit.ly/36P7cbd
You also need a start and stop switch to be connected to the PLC input.
- When you press the start switch, the coil will be energized, the contacts will be closed and the motor will be turned on.
- When you press the stop switch, the coil will be de-energized, the contact will open and the motor will turn off.
=============================
Missed our most recent videos? Watch them here:
realpars.com/capacitive-sensor
realpars.com/photoelectric-se...
realpars.com/inductive-sensor
=============================
To stay up to date with our last videos, make sure to subscribe to this TH-cam channel:
bit.ly/realpars
=============================
TWEET THIS VIDEO ctt.ac/3Q3o3
=============================
Follow us on Facebook: / therealpars
Follow us on Twitter: / realpars
Follow us on LinkedIn / realpars
Follow us on Instagram / realparsdotcom
#RealPars #Contactor #PLC
It's been more helpful this channel than my career in more than one aspect.
What an amazing compliment! Many thanks
Totally Agree 🙏
When a YT video explains much more clearer than my Engineer Teacher.
I am in industrial automation domain from last 2 years and have referred many videos. But the quality and vibrancy of Realpars videos us exceptional ❤
Thank you so much!
I'm going through the greatest challenge of my life: becoming an automation engineer in a industrial plant. I've got a degree in electrical engineering, which was more related to power supply systems, but not so much to automation... however, I accept the challenge anyway! And I have to thank You for sharing this knowledge in a so wonderful way! It's been very helpful for beginners like me!
We truly appreciate your support, Leandro! We're happy to hear that our video courses are helping you.
If you have any questions along the way, please feel free to reach out.
Probably one of the most lucid presentations on contactors I've run across. Great job!
Thank you very much, Ken! Much appreciated
So glad I found this channel when I was starting my career. Your videos are always so easy to understand with the good narrative and the images. Than you so much. One day I'll come back to buy your courses even if I don't need them at that point.
Amazing compliment, many thanks!
In the past year I have seen many Hvac videos. This is by far one of the best channels I subscribed to. I promise to share with some of my school mates. Thank you sir! Respect and keep the knowledge flowing on a high pressure gauge!
Thanks for sharing!
I have been waiting for contactor vs relay video since long. Thank you for this.
Glad to hear that! You're very welcome.
Amazingly simple and interactive way of explaining.
Glad it was helpful!
Very well explained in American-English, recently I did a L3 PLC programming in UK and it was horrible. Anyway, I took the certification...And by the way regarding the contactors and relays, you can always put three relays instead of a contactor for some small motors temporarily, just check the ampers. I have an Arduino controller with 230v 10A ,very small relays working even on 3.3v DC, so with them, I can easily switch On/Off a 1000W , 450V motor.
What if only one phase trips? Wouldn't that cause phase imbalance?
This was so helpful and helped me embarrass my lead for trying to troubleshoot a broken contactor incorrectly when it was working just fine!!!
thanks a bunch RealPars
You're very welcome, David! Glad to hear that our video course has been helpful!
Very informative video, and you explained everything with no way to misinterpret the information. Very nice!
Glad you enjoyed it!
I'm not an engineer but in hvac school. This video really helped. Thank you!
Glad to hear that!
Clear and great video thank you for sharing your experience.
Well thought out clear and concise presentation thanks very much
Glad it was helpful! You're very welcome.
Exceptional full scope of the content on the blog about the information about the contactors.
Congratulations on your exquisite work.
Many thanks!
What an excellent explanation of how a contact operates!🤩
Thank you very much!
Hats off to you RealPars. What a nice way of explanation!
Thanks a ton!
Excelent clear information. Congrat!
Glad you enjoyed it!
Excellent video by RealPars!
Thank you very much!
I'm very appreciated that you did this video. It's very helpful. I got the power & courage again. Thank you. I'll keep studying.
Glad to hear that! You're very welcome.
My fav TH-cam channel. ❤️
RealPars you best! Real learn videos! Thanks!
Glad you like them!
Fantastic intro to the topic! Thank you.
Glad you liked it!
The very best video on this topic!
Thanks a lot, Bill!
Really good video explaining things clearly and easy to understand. Many thanks.
Glad it was helpful!
This channel is really damn helpful for technician and engineers working in industries..
We're very happy to hear that, Natesan! Always feel free to leave us your questions if anything is unclear.
Thanks a million for your support!
Very simple and understandable explanation thank you realpArs
Glad to hear that, Ahmad! Happy learning
Great video. Remember one thing. You must connect a thermal relay in series between the outputs of the contactor and the inputs of the motor, plus the output that indicates a overload as a signal to PLC.
At that point why not just use a VFD instead?
...and now you have a motor starter and not a "contactor".
Wonderful explanation. Thank you so much 👍
Glad it was helpful!
Your videos are very useful to learn and I would say that I like the way of teaching through the awe animated videos..Thanks.
Happy to hear that!
Thank you for the great and simple explanation
You're very welcome! Happy learning
I'm very confused about those,now I'm cleared. thank you
Glad to hear that this video course helped you clear out the confusion. Happy learning and keep up the learning curve :)
this video explained the essence to me more than anything existing on TH-cam
That's amazing to read! Thank you so much for your kind support
These videos are great,although you can be in maintenance field for many years it’s always some details and concepts you may miss but going back and studying and just doing a little research clears up a lot of the fog that can be in you’re head about certain things
Thank you very much! We're very happy to hear that.
Why did I only come across your channel now? Very well explained. Thanks
Glad it was helpful! Thank you very much
Love this channel
Thank you!
Now am clearly understand about contractor and relay thank u realparas
Glad it helped!
Brilliant, very clearly explained, and very good visuals, thank you sir
Glad it was helpful!
Thank you! I'm from Brazil.
Our pleasure!
Finally my question has been answered
This is the best ❤
Glad to hear that, Ibim! Happy learning
Thank you very much for this video
Glad it was helpful! You're very welcome
It was so helpful, thanks a lot!
Glad to hear that! Thank you for sharing
Very well explained I saw it many times easily understood thank you so much for this information..
Glad to hear that! Thanks for your support
I Praise God and thank those who have designed and worked on (and may continue to do so) such things as this to make things safer and to help prevent damage to other things. I imagine that some or all of the specifics to the design of such things may have required much work and testing. God Bless them.
Awesome video, great explained!
Glad you liked it!
Yes, video has been very helpful!
Glad it was helpful!
Great explanation. Hat's off..
Glad you liked it!
OMG thank you so much, this video is very helpful!!!
You're so welcome!
Thank you so much for making this video I'm just starting my career in this feild and this video was very simple and helpful
Glad it was helpful!
Nice introduction with the connection content of PLC, like it!
Glad you liked it!
Best video ever. Keep up the good work
Thank you, Sanele!
Perfect explanation
Glad you liked it
Wow that's why i like all your videos
Very lucid and audible, your videos are the best. How I wish you could have established a training center in Africa for hands on training 🤷🤷🤦 Kindly also do a video on electronic modules 🙏🙏
Thanks for your kind comment, Kasonde! I will happily pass your topic suggestion on to our course developers.
Great Explanation 👍
Glad it was helpful!
Amazing explanation!!!!very nice channel
Thank you so much, Gilberto!
very well explain. thank you sir.
Glad you liked it!
thank you, well explained
Glad you liked it! Thank you for sharing
❤ beautiful explanation
Thank you!
Thank You Real Pars
You're very welcome!
Amazing video, I really love this channel.
Happy to hear that, Khaled!
Impeccable teaching, thank you ❤️
Glad it was helpful!
Thank you very much, i like this video
You have a very good way to describe
Thank you, Garo!
Neatly explained, thanks!
Glad you enjoyed it!
Simply superb sir 🙏🙏
Thank you, Kuppili!
this is an amazing and awesome video. keep it up sir. thanks for teaching us💖💓
Thanks for your kind support, Zubair!
Such a helpful video.
Glad to hear that!
Useful video thanks realpars
Glad to hear that!
👍 so nice and easy. Thank you for good work.
You're more than welcome, Ihab!
I realy love your videos, they are very helpful.
Thanks a lot, Xuan!
Nice video! Thank you for sharing
Glad you enjoyed it!
Thank you very much for valuable information.
Kindly make a video on Different PLC programming languages available and their applications and their best uses.
Thank you very much for taking the feedback and making the same.
Hi Maruthi!
Thanks for your comment and your suggestion. I will pass this on to our course developers!
Thanks for sharing and happy learning!
really Appreciate the Basics 👋
Glad you like them!
Thanks for the great video, I love your channel just wish you did more on AB.
Thanks for your kind comment and feedback, Lukas! I will happily pass this on to our course developers.
Well done good job , thank you
Our pleasure!
Thanks very helpful 😊
Glad it was helpful! You're very welcome
beatiful and helpful... you have a new suscriber
Awesome, thank you!
Clearly understood sir thank you
Glad to hear that!
Great explanation about contactor
Glad you liked it!
Thank you soo much you help me a lot
We're so glad!
Thank for your video❤
You're very welcome!
Awesome... Excellent work❤
Thank you so much!
Hi! I really like your videos, congratulations for the excellent manner in which they are presented. They are an excellent training resource!
One question: I keep seeing in your videos that you mention a -24V DC connection when in reality it should be 0V (M in schematics). When you say +24V in the positive connection, and then -24V in what should be the 0V (M), it gives the wrong impression of a net 48V potential across the supply of the contactor coil. I've seen other of your videos that also have this mistake (not exactly of contactors by the way).
Am I missing something?
No, you are not missing anything. Having designed and installed hundreds of panels over my career, I have seen a few different ways to identify the negative, or common, connection for 24VDC circuits. Technically, the return leg, or more negative connection, in a 24VDC circuit is identified as 0V, earth potential, or COMMON. However, some like to identify the common terminal as the (-) terminal or the negative terminal of the 24VDC circuit (-24VDC). This designation is designed to separate it from other grounds or earth potentials.
I always say "DC Common" or "DCC".
Perfect animation
Thank you!
Excellent work ❤️
Thanks a lot!
Thanks u very much realnpars
Always welcome!
Very helpful 💯💯
Glad to hear that, happy learning!
If I remember correctly, contactors use a bar across two contacts per line where it can split the voltage to prevent arcing, whereas a relay uses only one point where it will experience the full voltage drop across the contacts, when opening the circuit, so a relay will take damage when opening a higher voltage/higher current source when the contactor is designed to split the voltage across the 2 contacts and reduce possible damage from arcing.
This is correct. The contacts in a contactor are also larger than a small relay and have contact surfaces designed for higher currents. Often the contacts in a contactor will also 'wipe' or rub across each other slightly as they close, this serves to clean off slight oxidation traces and keep the contacts fresh.
the double breaking does not cancel the electric arc but helps to extinguish it, which will define the breaking capacity of the contactor.
Much of the complexity of contactor design lies in implementing different arc breaking techniques in a minimal amount of space.
it is this electric arc which determines the electrical life of the contactor (because of the progressive degradation of the contacts) which is much less than its mechanical life which is often around ten million operations.
The electrical life depends on the type of load supplied by the contactor. An inductive load will generate larger arcs than a resistive load and decrease the longevity of the poles. The contactor manufacturer gives life curves as a function of use to provide for the replacement of devices.
this is amazing, thank you
Our pleasure!
I am from Bangladesh and EEE engineer.ur video helps me a lot
Glad to hear that! Happy learning
Very Helpful 🔥🤩
Glad you think so!
Thank you
Good job guys!
Thank you, Bartosz!
I love this channel.
Glad to hear that, Lola!
Hello Real Pars, I enjoy watching your videos. Undoubtedly, I have learnt a lot through them. I have a request. Can you please make a video on phase monitoring relay? I'm having a challenge understanding it. Thank you
Great suggestion, Cletus! I will happily pass this on to our course developers.
Thanks for sharing and happy learning!
Howdy. Nice basic knowledge.
However. I would be reluctant to connect a contactor coil directly to a PLC output. I would use a relay in between.
Also a backfire or free-wheeling diode over the contactor coil is mandatory with DC. There is a lot of induction in the contactor coil when engaged. This energy will rapidly burn the relay or PLC card contacts if not managed. With AC the backfiring problem is not as big but some backfire managing is still necessary by a suitable RC filter over the coil. Typical values are R = 100 ohm and C = 100 nF 500 V in series.
Regards.
Thanks for sharing your knowledge and experience with us! We always appreciate such comments.
@Mindaugas Vaitiekūnas Yes.
The backfire diode is a good solution in most cases. It is sometimes experienced that the contactor disegages too slowly as the back current takes too long to dissipate in the coil and the diode.
A solution to this may be to use, say, 7 diodes in series. This will force the back induction to rise to about 5 V and provide a faster dissipation.
The output transistor will see a voltage of 24 V + 5 V, or some 30 V but it will most likely tolerate that.
One could consider using a regular diode and a 5 V zenerdiode in anti series but it is not recommended. Zener diodes are slow and will allow the build-up of a high spike before going into conduction.
For the same reason Schottky diodes cannot be used.
Regards.
Very useful video.... Keep it up 👍
Thanks a lot!
Thanks for the video
You're very welcome, Peter!