MCB - Circuit Breaker - How does it work?

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In this video we will look at the popular Miniature Circuit Breakers and find out how they work. Using very simple drawings we will discover the two modes of operation and look at how to interpret and use the time and current tables to which they must all adhere.
Understanding how they work and the two modes of operation is very useful in fault finding on circuits that have tripped. Knowing in what manner they tripped can often give clues as to where to start the fault finding process.
This video is No.116 on our RU-vid channel where we have videos on a wide range of electrical topics.
To see a full list of all our LearnElectrics videos, click on the link below.
/ @learnelectrics4402
You can also view all our videos by typing LearnElectrics all one word into the RU-vid search bar.
Always work safely, electricity can be dangerous. If you are unsure, stop and seek advice.
This video is provided for guidance only. Every electrical situation is different, please check and ensure that you are applying this learning information to your own individual circumstances correctly and safely. If in doubt, stop and seek competent advice.

Опубликовано:

23 июл 2024

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Комментарии : 31

@mb-electricalservices 2 года назад

These videos are the equivalent of finding money you forgot you had. Brilliant guys! 😎👍

@learnelectrics4402 2 года назад

Thanks Mike, great feedback and much appreciated. Dave.

@peterrobinson850 2 года назад

Hi Dave, From an old spark from the 60's. Yet another excellent well presented explanation you've got the gift just like Joe Robinson, I've seen others try to explain the same thing and made it overly complicated, top marks. Peter.

@learnelectrics4402 2 года назад

That's a great comment Peter, thank you. I try and make them understandable. Thanks for your support. Dave.

@orestismiaris4928 Год назад

This is gold thank you very much!

@learnelectrics4402 Год назад

That's great feedback. Thank you Orestis, really appreciated. Lots more to come. Dave.

@johnhalse2779 Год назад

Thanks Dave - you present very well. Cheers Halsey

@learnelectrics4402 Год назад

Thank you kindly John, much appreciated.

@spcyman7209 2 года назад

Very good explanation, Dave. Keep them coming.

@learnelectrics4402 2 года назад

Will do. Lots more to come. Dave.

@hypermotard617 2 года назад

Thanks for the great videos, please keep up the good work 👍

@learnelectrics4402 2 года назад

Thanks, will do Scott. Dave.

@30mAkills 10 месяцев назад

Simple to understand

@learnelectrics4402 10 месяцев назад

Glad it helped, thanks for the support. Dave.

@ifyougetstucklookitup237 2 года назад

Thank you.

@learnelectrics4402 2 года назад

You're welcome, glad you like them. Dave.

@stuffoflardohfortheloveof 2 года назад

Thank you, very interesting and I now understand both the mechanism and the table. My only comment would be that when you showed the reg table (and then your simplified, coloured version) you didn’t state what the line (with the knee) ACTUALLY signified…..ie if you simply said “this line is when/where the MCB trips” it would have immediately made it all clear. Not a criticism, just pointing it out. Thanks for posting 👍🙂

@learnelectrics4402 2 года назад

It does actually say in the video. The point at which the MCB operates almost instantaneously. The MCB can trip before the knee too if it is a thermal response. Have another look at the video, it is there. Hope this helps. Dave.

@Trade920 2 года назад

Great video Dave so simple to follow, i do have a question tho please. How would the cable hold up with such long tripping times as explained at 10:30? lets say the 20amp circuit scenario is a 2.5mm twin and earth cable and was carrying the mentioned overload current for 2000 seconds or 33 minutes. That cable is designed to only withstand 26-27 amps normally thats if it is not buried in insulation, so i appreciate 30 amps isn’t a great deal more than what the cable can withstand, however, What could be done more to protect the cable from overheating/melting or in more serious scenarios where there is more fault current flowing potentially causing a fire under these slow trip times? Sorry if this is a daft question but i’m just trying to better myself Keep up the great work love the channel

@learnelectrics4402 2 года назад

That's a good question and logically it doesn't add up but this is the standard to which the MCBs have been manufactured and we assume that they know best. I just use 30 amps as a classroom example to show that not every overload will cause an instant trip. Most often though it may be two 13A devices (kettles) and that is less than the cable max. Not a daft question at all my friend. keep them coming and thanks for watching. Dave.

@Trade920 2 года назад

Thanks fpr replying dave 👍

@hussamalsalem2438 Год назад

Thank ssssssssss

@learnelectrics4402 Год назад

Thank you Hussam, appreciate your comments.

@zazugee Год назад

this explains why TN schemes need very low impedance earthing, it's because those MCB need a very high current to trip faster

@learnelectrics4402 Год назад

You've got it. Thanks for watching, hope it helped. Dave.

@deborahskeete 2 года назад

Please do a video on the whirlpool jetbath

@learnelectrics4402 2 года назад

That's a thought Thanks.

@learnelectrics4402 2 года назад

Thanks for watching.

@maxwang2537 4 месяца назад

I don't understand why slowly changing current will have no, or little, electromagnetic effect. I believe this is wrong. I suspect you are confused by the difference between this and the property of inductor, which resists rapid change of current. Please correct me if I'm wrong of course.

@learnelectrics4402 4 месяца назад

Thanks for your input.

@maxwang2537 4 месяца назад

@@learnelectrics4402 thanks for your video. It’s still very helpful.