How Does a Circuit Breaker / Trip Switch Work? - Pt 1
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- เผยแพร่เมื่อ 5 ต.ค. 2024
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In this video:
We take a look inside a thermal magnetic circuit breaker to see how it works with both AC and DC.
I do a practical demonstration on how the circuit breaker works to protect against overloads and short circuits.
We take a look at some circuit breaker ratings such as:
In: Rated current - maximum current that the breaker is designed to carry continuously at an ambient air temperature of 30 °C.
Icu: Ultimate short-circuit breaking capacity.
Ics: service short-circuit breaking capacity.
I test what parameters (voltage vs current) affect the overload protection of a circuit.
I demonstrate the instantaneous breaking / tripping capability of a circuit breaker on an oscilloscope under various loads.
I show circuit beakers that are designed to cater for electric motor start-up inrush current with an adjustable instantaneous trip setting.
en.wikipedia.or...
Understanding Electric shock / Electrocution:
en.wikipedia.or...
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This is such a good explanation of how the circuit breaker works. It should be taught in school rather than Chaucer and Shakespeare. Another great video. Thank you.
alex tworkowski could do both
Thank you for the effort in making such a detailed presentation. It helped me understand the importance of using a well designed and reliable breaker.
Excellent demonstration. Inverse current time duly demonstrated. Great effort Mjlorton
easily the best video on YT for the topic! comprehensive and clear
Great work learned this thirty years ago but now I learnt it all over again . :)
Really really well done
.
hey mjlorton. I really admire your work and the effort you are putting into publishing these tutorials for general public as I have gained a lot of information through your videos which helped me in many ways. Keep up the good work and we will continue to show you support.
If i may, I would like to request you if you can upload videos on complete working of Electrical Standard products like Air Circuit Breakers, Moulded Circuit Breakers, Changeover Switches, Contactors & relays, basically all Switchgear Products. It will be of further great help than from what I have already been receiving from you. Cheers.
good work. I have no knowledge about electricity.
You may save my life by making this video. thanks
Excellent demonstration as always. Cleared a lot of concept in this video. Great work.
hey Martin, thanks for the in depth analysis of how breakers work, thanks mk
Just a note a circuit breaker in the distribution board is only to protect the fixed wiring, which is in the walls, not the equipment attached. You need another protective device inside equipment to handle failure inside the equipment.
In the USA you will also come across RCD outlets and AFCI breakers, which serve a different function to a circuit breaker, though the protection function of the circuit breaker can also be added to it, and in most cases already is.
SeanBZAThanks, my mistake...adding an annotation now.
SeanBZA Not true everywhere, in parts of Europe (not the UK) the fixed breakers in the board DO protect at least part of the appliance (usually the cord)
***** Not unless the cord is rated to survive. A 20A breaker will do very little to protect a 0.7mm cord ( like on a clock radio) from melting, until it gets to the point where it shorts out, which very well might be well after the fire is raging. On a 1.5mm cord it will provide some protection, but it's main point is to prevent the 2.5mm wiring in the house from burning if say you connect a 2 kW heater to the outlet and then connect a second 2kW one to the same circuit from another socket, then plug in the 1.5kW vacuum cleaner to do the floor.
***** Does this not still happen? (20 amp earth bond test) ?
Have a qualified electrician use a clamp-on amp meter to check the circuit load. If the load is within the limits of the rated breaker, then replace the breaker as they have been known to go bad.
Good ! Hopefully, next ep will be shed some light on the In-Line GFCI Ground-Fault Circuit interrupter.
As already mentioned before, when you connect a source of constant current to the circuit breaker, doesn't make sense to test changing the voltage of the power ... the time of break-out will be always the same. Anywhere, the video is very interesting !!!
oh wow! this was a very educational video..well done!! I learned a lot...well done
Thanks you for your explanation and demostration because your video was fully understood me how to work the breaker cutoff.
Excellent video and explanation. Great to learn and clear concepts by watching these educational videos.Looking forward to watching some more. Great job.
Maybe a part 3 can cover protection more downstream of the breaker box such as: AFCI breaker outlet, isolation transformers, and power regulators/conditioners.
thanks for the indepth explaination looking forward to seeing pt2
cheers
quite comprehensive, thanks, looking forward to new videos on new topics.
Excellent job you did with this video.
Nice,,very informative video.. Looking forward to see the second part..
Very very very great explaination
so was detailed and help the researcher more understand
Very interesting, thanks for the infotainment. It would've been cool to design that kind of system. The amount of features and functionality you need to satisfy require a fair bit of engineering vision.
Why the hell has someone thumbed this down? Some people just hate education
bad formatting, too many tangents. Don't assume they don't like learning.Accept people's criticism.
You should do one of these for earth leakage breaker (ELCB)
This shows the importance of cct brkr box location. Out in the open air or outside wall, winter temps increase trip time.
Nice work bench Im impressed
#25:42 The reason the voltage setting of the power supply is independent of the Thermal Trip Unit (TTU), is because the two are independent variables: the power supply is acting as a current source and the (TTU) is a function of the I^2R dissipation in the Bimetallic Strip. In this case 376.36x Bimetallic Strip resistance. The power supply is operating in current limit by definition: see the Clamp-On ammeter 19.4A reading in this case. The voltage setting of the power supply doesn’t come into it.
“...In this case with the heating of that Bimetal strip, it’s not the power but it’s the current you are carrying through the breaker that will dictate the time in which it takes to break…”
No, it’s power that determines the TTU. Current, in and of itself, is not a measurement of energy. This can easily be demonstrated by putting an automotive incandescent lamp in series with a mains incandescent lamp across the mains supply. The automotive lamp will glow while the mains lamp will be almost full brilliance: despite both shipping the same current. In the UK, this was taught at ‘O’ level physics back in ‘79.
Excellent demonstration. Thank you. BTW, I may be wrong but you have a South African accent?
Excellent looking forward to part 2!
Great teaching. thumbs up!!
Good info in video and the comment section, nice job.
A lot of details about types and markings of breakers in the first half of the video. "Useful", but the images gets pretty first at 11:15 and the really interesting part is at 15:54.
When I was young I had a nasty shock from a AC to DC 9V adaptor, direct from a 220VAC @ 20A) I remember the period I held on due to the muscles in my hand contracting was for approximately 8 seconds, It was a disaster, I manage to let go (I don't know how) After that, I could not use my hand for a whole day. I've never shocked again, and hopefully wont have an experience like that again. its no joke safety first, always use a fuse and common sense.
***** did you tell your mom?
Beryllium yes my dear troll
Great video and explanation. Now, I 'd need to know how to install these things, for example, I need to make a separate line for all kinds of outside appliances, a line to my garage and other buildings outside the house, but I want to put one of these breakers on that line at the house, so if I need to mingle with the wires, I can switch that off, not the main breakers and leave the house without electricity, just these, and safely work on the wirings there, so what kind of CB would I need if I have an incoming line with two wires, one is obviously L and the other is N. Is it enough with a single pole breaker for this situation?
You should measure the voltage across the circuit breaker...
Brilliant video and very well explained, thanks
I cringe when people talk about a certain amount of current that it takes to cause a person to be injured. Voltage is the primary thing that does it. It takes voltage to overcome the resistance of the body and cause the current to flow. You can hold onto a battery that can deliver thousands of amps, but if it's only like 1.5 volts, it's not going to harm you. The current that can be delivered from the voltage source is the secondary cause of injury. Think static electricity. In general, there is little current capacity behind common static electricity. It obviously can deliver the voltage to overcome the resistance of the body, and you can feel it travel through you, but it can't deliver the current.
Great video, thanks, looking forward to part 2!
I wanted to know-
1)When does the solenoid pushes the lever to release the arm?
2)Use of solenoid.
+Saurav Vats in the event of a high (surge) overcurrent state - say, 100A on a 20A breaker - the solenoid gets energized with enough force to release the latch
Fantastic video !
great video, great explanation, but you certainly have a slow reaction time, lol :D
I feel I should point out that unless you're running the trip tests through a constant-current dummy load, your voltage setting is irrelevant, as the power supply will be in constant-current mode and only delivering the voltage needed to drive the desired current.
That said, the voltage won't make any difference to thermal and mechanical trip time anyway.
Monkeh616 So are you saying that if you have a constant current that the voltage has no bearing on the activation of a solenoid?
mjlorton As far as I know, the voltage won't make any difference to the solenoid, either. It is the current which generates the magnetic field, just as it is the current which causes heating in the bimetal strip.
These breakers should operate from practically no voltage (as you would have with a power supply shorted across them in constant-current mode) right up to the point they're incapable of arc suppression. This will not be true of all types, however. AFCIs I believe, certainly GFCI/RCDs, combo devices, devices with programmable tripping characteristics, etc, will require a certain voltage to operate.
For bonus points, measure the voltage across the breaker at rated current and determine how much power is lost in it.
Monkeh616 Correct, voltage has no part in the trip on ether thermal or instantaneous trip, the only voltage is developed across the breaker internal resistance, but it is the heating from the current that is activating the thermal bimetal time delay on low overload ( what is being tested here) and the high current through the solenoid coil to pull the internal slug across the magnetic field ( the core of those is a lot more complex than a simple solid metal slug, there is a moving pole piece inside that is pulled into the solenoid coil to provide an impulse to trip the breaker, held in place by a weak magnet in the core) on large overloads, where the thermal trip is too slow to clear the fault before the wire overheats.
That is why there are very few purely thermal breakers in house wiring, they require a thicker cable to withstand this overload condition. Here in South Africa the original thermal only breakers from the 1960's required a 4mm cable to ensure it would have enough thermal overload capacity. With the introduction of the thermal magnetic breaker ( as shown here and almost universal in premise wiring protection) you did not need the thicker cable, as it would provide protection to thinner 2.5mm cabling safely.
The voltage rating is there for the breaking function, too high a voltage and the arc suppression will not provide adequate arc breaking capacity, which will rtesult in an arc that will self sustain till the breaker burns out and the supply cabling burns off enough that the arc goes out, or an upstream fuse or breaker trips out disconnecting the whole supply. That is why you often have a DC rating so low, as the arc does not tend to go out 2 times per mains cycle, but only when it is either cooled by the arc suppressor cooling off the plasma below the ionisation temperature, or it grows so long that air cooling does that. A nasty demo is to take one of those AC breakers and use a 48V supply from 4 series connected car batteries, where the arc will not extinguish ( though I would not recommend closing the breaker into that but use another larger DC rated switch instead) but will carry on burning even with the breaker opened. I might do a video using a 140A arc welder and a sacrificial 5A DIN breaker, like the ones used, to show that, as I should get a high enough current to make a sustaining arc from that. Going to be fatal for the breaker in any case.
mjlorton
Yes, that's the whole point of the constant current setting. In an over-current-limit situation the PSU reduces the voltage below the value you set until the current is at the set limit.
I guess in all your tests the "current" LED was on? This means current is the limiting factor and not voltage. And unless you have a very weird PSU you should have seen the voltage on the display drop (to the same value in all of your tests). PSU normally show the real outpur voltage and not the one set under no load.
Also how could the voltage make a difference when the current and the resistance stay the same? It's Ohm's law.
The voltage WILL make a difference though if it's about extinguishing the spark. At higher voltages it will (obviously) take longer, but that's at values way out of that PSU's ranges.
superdau Yup, thanks for the post. I certainly went down the wrong rabbit hole. I'm going to follow-up with another video covering that mistake.
Cheers, Martin.
Awesome information! Thank you!
Maybe I missed it, but I thought he said that in certain conditions, the switch will not re-activate the breaker... What condition is that? Is it the spring loaded coil thing? The heat will dissipate so long as the circuit is broken, but what makes the spring coil thing activate?
Off-topic: When you doing a review of the Fluke 867B? (I ask, because I have one, and wondering if you have the same display issue, and for other things I have missed ;p)
thanks a lot. Just one question, how the plunger is operated during sudden high overload (referring to time stamp 12:30)?
I'm nit picking here, but when you say "DC 50 Hz 60 Hz" (describing the little black breaker) it might be good to qualify that DC power can't be 50/60Hz for the people who may not know that. It's either DC power, or AC power (at 50/60Hz). Cheers.
best demonstration thank mate
great explaination
I got a question. Why do they use the 2 metal strips if the solenoid itself can break the circuit way faster than the metals?
Very nice and informative. Thankyou
In my circuit breaker the copper wire is breaked down ,what may be the problem there's also some black patches on the plastic cover as if it has been short(spark)
For some reasons, that heat bending stuff got me disappointed... I don't know what I was expecting though...
Does that mean that a circuit breaker that is in a cold place (say a cold Canadian garage in winter) would take longer to break or even not break at all?
Really good video
how would you go about seeing how a motor protecting circuit works. wtnpd 22-551 in a floor 1 1/2 HP scrubber ??
Thank you! Nice job. What temperature is needed to break the circuit? If the circuit breaker box on the outside of house is in direct sunlight, would that maybe cause circuits to break more often than normal, or is that too low a temperature to have any affect on the thermal strip?
i think yes .. i work in lab service in summer season there is increase in mcb fault i observed
very nice video.
It is normal for main circuit breaker to be a little hot at time? Mine once in a while trip, I dont think my appliances is shorted as
it could be reset. I think maybe it is too old, mine house is 25 yrs old, Ty, I may change a new one myself. My electrician in Spore is vy exp,
want to charge 200$ just to change this MCB which i can get for 20$..
My MCB are both electromagnetic for short circuit and thermal for overloading.. ABB S202 type2 40A
God bless you
It was a good description until you started talking about the voltage in the circuit.
The voltage in the circuit has no bearing on the results, (unless you measure across the breaker).
All you are doing is using the wiring as a resistor. The power supply lowers the potential to limit the current.
I've never seen a circuit breaker where the switch remains in the 'on' position after it trips. Is this something that differs between countries? How do you tell which breaker has tripped in a household panel if they are all showing as on?
Dear Sir. If your company is stay in South Africa? I know the ONESTO very well. because the manufactory is nearby our manufactory.
Wow that was really helpful!
Fantastic video, thanks
Is it possible to just insert a metal wire across your heart to protect it?
Good video.
Hi mate, I couldn't find a message box so all I can do is ask you here.
Myself and a couple of friends grow silver perch in 1000 ltr tanks, is there a device we could get that will monitor a water pump and switch on another water pump when the primary one has died . My friend recently came home to find his fish nearly dead because his water pump had died.. We don't want to use battery backup..
Thanks Martin.
great video
Dude, it was exhaustive for me ! Had you been teaching in MIT ? I will need some reference documents to understand, what you say ! :)
how is this breakage instantaneous if the bimetal strip needs to get bent all the way for the break to happen
Great video
will dried up salt water prevent the breaker from tripping ?
Hi there
I just want to ask about the circuit breaker if it has input and output or not
Thanks
P=(I^2)*R interesting what is the resistance of bi-mettal, mjlorton ??
thank you for this video
I stumbled here and got lost in this video for 20 minutes. I should go back to school for engineering.
college is school
22:13 If you use 50A, after how long the CB will trip?
nice information thank you.......
Hi sir..can i use some part of your video for my youtube tutorial video? I will credit your link in my description. Thanks sir.
About how many times can a circuit breaker trip before it needs to be replaced?
***** which means that the switch wouldn't hold anymore, right?
TheEnneagram when the contacts of it get dirty by the arc and then you start noticing it heats more than usual with the normal load. That means the contact having resistence.
+TheEnneagram how many times can a circuit breaker break before it breaks?
Andrew Geng How many licks does it take to get to the center of a Charm's Blow Pop?
chines low quality mcb goes crack with 5 to 8 times it trips and high quality breaker keep working again and again ......life long
My automatic circuit breaker buzzing whenever i'm turning on my water heater. Is it dangerous or can harm other electronic devices likes phone ar laptop? It buzzing calmly when i'm charging laptop battery but a bit loud when i'm turning on my water heater. What should i do?
I was of the understanding that AC Voltage shock will throw you off and DC Voltage shock will clamp you to the fault.
good info
voltage on a closed wrench to zero and it is useless to turn it on the power supply
thanx for useful vedio
23:25 what kind of clamp is that?
Great
How could i measure RPM with an optical breaker circuit
Very cool
it is 1976 i woking in bukatir's group & i found a complain in building belong to Health Club The Floor Wiring have problem of Ac's Wiring Ac's wiring Size problem Thank
GOSTEI
It's almost THAT art of youtube
good
Have you ever seen a main breaker turn off ? Not trip but actually be turned off it's been happening for the last 3 months at random times.....
11:20 is when he takes it apart
CE is made in PRC
Yes. you are correct.
Ok i decided to put a ground wire and we fixed it
go to 11:15
thank some mcb's have menufecturing male function they do not write the crect informetion technicaly even on of posetion to locete the in emergency on of thank