Why Circuit Breakers DON'T Protect People (electric shocks)

Sponsored by Brilliant Will this

circuit

breaker save you from

electric

shock? No, none of these, why? Well, this number here tells us that the

circuit

breaker is rated at 3 amps of current and is one of the smallest ones you can buy for reference. about 0.14 amps, this toaster is about 3 amps and this hair dryer is 7.8 amps. His body has a very high resistance. We can touch a low voltage battery and nothing really happens, but the wires in our homes have much higher voltages. If you touch them, current can flow. Straight through you with only 20 milliamps your muscles contract and you probably won't be able to release them at 0.2 amps for 1 second and your heart may stop beating so this 3 amp breaker won't trip and will save you. just provide power to everything connected Ed including you, in fact even this 3 amp toaster won't trip this 3 amp breaker.

This card tells us that and I will explain it later in the video, so if it doesn't

protect

people

then what does it

protect

? protects wires and property and property is expensive why property well, current flows through the wires in our properties inside the wire there is a metal conductor that provides a load resistance path to the

electric

al charge, this It is covered with an insulation to protect us and prevents the current from taking alternative roots every time current flows through a wire it generates heat. Now this is not a problem, but as the current increases, the temperature increases and at a certain point the insulation weakens and eventually melts, exposing the metal. conductors and even causes fires Each size of wire is rated for a certain maximum current, so the circuit breaker should not exceed that value.

The circuit breaker will detect excessive current and automatically trip to protect the wire. It does this using these internal parts which I'll explain in just a moment, if we run 20 amps through this 10 amp breaker, how long will it take to trip? Tell me in the comments section and I will give you the answer at the end of the video to protect

people

we use another device that measures the current flowing in and out of the device, then it trips if these two values ​​are not equal, but that is a topic for another video. This circuit breaker only detects short circuits and overloads.

Normally, current flows from the line through the load and back to the neutral. It is AC current so it actually flows back and forth but I will explain it as DC for simplicity, the resistance of the load limits the current but if the line and neutral come into direct contact then we have a short circuit because there is no resistance, so a huge, instantaneous surge of current occurs and trips the circuit breaker instantly. We know that the circuit breaker is rated for a certain current every time we plug and connect the appliance. We increase the current.

Eventually we will exceed the limits of the circuit breaker and it will trip. This is an overload and takes much longer to trip, we can manually operate the circuit breaker to isolate the power, but it will trip automatically once the fault is cleared, we can manually reset the device even if the lever is kept in the on position, most devices will still be able to activate. trip and that's thanks to clever internal design, most of the world uses these mcbs for residential uses, but North America and some other places use plug-in circuit

breakers

, although mcbs are still often used in industrial and control applications in those regions, each manufacturer has a little different design, they all work very similarly, but you should not mix them.

This is a consumer unit installed in the UK. We can see that it has many mcb. Remember that electricity is dangerous and can be fatal. You must be qualified and competent to transport it. When carrying out any electrical work within the consumer unit, we have the incoming current and neutral supply. This enters a two-pole main switch. The current passes to the rcd and then to a metal bus bar which connects to the bottom of the rcd and this will provide power. to multiple circuit

breakers

a wire runs out the top of the circuit breaker to the load a neutral wire then runs from the load and back to another neutral block this block connects to the rcd the rcd connects to the main neutral block and this connects to the main switch so that current flows into the live through the main switch into the rcd through the circuit breaker through the load and into a terminal block, then back through the rcd to the main terminal and out through the main switch to complete the circuit, although since this is AC electricity the current actually flows from one side to the other looking at the circuit breaker we find a notch on the back that allows us to clip onto a rail d this rail is not electrified on the front we have a lever which moves up and down and also indicates the status usually there is an indicator window there is also a lot of text which I will explain later in the video we also find two screw terminals that allow us to adjust the terminals to hold a cable or bus bar in the top and bottom, be careful as it can go behind giving a false connection and you definitely don't want to often have a heat vent at the top and at the bottom we see a small hidden screw.

I will explain that at one point I had to drill out the rivets, but then we can remove the case to see all the strange parts inside. Each manufacturer has a slightly different design but they all work very similarly. Basically we have a bimetallic strip for overload protection, a solenoid for short circuit protection, a lever, a mechanism with a movable contact and an arc chamber, as well as two terminals in normal operation, current flows through the lower terminal along from the track through the biometal strip through the braided wire to the movable contact arm through the contact pad into the copper track and then into the wire around the solenoid coil and then out of the wire and through the top terminal and then goes to the load, the contact arm simply moves away to break the circuit to understand how it works, we start with the main lever and notice that it has a small spring The spring pushes against the case and forces the lever into position off.

Below we see the mechanism which has three main parts in the center is the main arm which is held in position with a pin. The arm can rotate around this point. There is a metal contact plate. Attached to this arm when the arm moves, the plate also moves. A spring is attached to this arm and pushes against the case, forcing the arm down. A trigger arm sits on top of the main arm and can move a small amount around the same pivot point. The trigger arm has a small opening on the end that lines up with a channel in the main arm.

A small spring pushes against the trigger arm and main arm, forcing the trigger arm to rotate and close this gap. A metal link is inserted into this space and connects to a hole in the lever, the main arm and trigger arm partially surround this metal link when we rotate the lever, the metal link will also move and follow the rotation of the lever, this pushes down on the main arm, causing it to also rotate, which compresses the spring. The lever cannot advance any further because the main arm spring is now pushing firmly against the metal link, the spring tension in the trigger arm is sufficient to hold the link in place, but if a small downward force acts on the The trigger arm will move and release the metal link.

The main arm spring instantly forces the arm down to the off position. This happens so fast that we need to sit in slow motion. You can see the trigger arm move and release the metal link. The main arm spring instantly moves the arm opening the circuit The spherical strip and solenoid can activate the arm and trip the switch The spherical strip protects against overloads is made of two different metals joined together, each with a different coefficient of thermal expansion in This version you can see the different colors of the materials there are other designs it just depends on the manufacturer when the strip is heated one metal expands slowly the other expands much faster which causes the strip to bend the current flows through the strip biometallic which generates heat and causes the strip to bend the braided wire allows some flexibility, but if too much current flows the strip will push against the trigger arm and trip the circuit breaker.

There is also a small screw here that the manufacturer uses to ensure that the strip bends into the designed position. current flow level you should not make adjustments yourself the next part is the solenoid which protects from short circuits this is simply a coil of wire connected through the top terminal and a copper track is held in position by a metal bracket and trim The box inside the coil is a plastic box with a spring-loaded piston inside the spring that forces the plunger up, but we can easily move it. The full circuit current will pass through the coil in normal operation, but the piston will not move, however, if there is a short circuit. circuit occurs, the piston will immediately be lowered until it hits the trigger arm, which activates the mechanism and cuts off the power.

Let's see that in slow motion you can see that the piston is lowered and activates the mechanism. Why does this happen when we pass current? a wire generates a magnetic field if we reverse the current the magnetic field is reversed we can see that by placing some compasses around the wire the greater the current that flows through the coil the stronger the magnetic field will be and if we wrap the wire in a Coil, the magnetic fields come together and create a stronger and larger magnetic field. The wire is coated with Van insulation, so current has to flow through the entire coil, otherwise it will take the shortest path and create a short circuit under normal conditions.

A field is generated, but it is not enough to overcome the force of the spring; However, during a short circuit there is very little resistance or impedance, so the current instantly increases to potentially thousands of amps, which will create a very strong magnetic field that easily overcomes the spring. force and pull the piston down our circuit is using alternating current so the current actually flows back and forth, the piston will be pushed down no matter the direction. You may notice that this small circuit breaker has a very thin wire with many turns to help increase the strength of the magnetic field, but the larger current R circuit breakers have much thicker wires and fewer turns, so both the bimetal strip and the solenoid can activate the mechanism and break the circuit, but when the contact point opens, we often find that an arc is formed because there are many The amount of energy flowing in this arc is extremely high temperature and could easily melt through of the casing, so we use an arc chamber.

This is simply multiple parallel sheets of metal, usually steel or copper-plated steel, held together by an insulating material. All plates are electrically insulated. one from the other, a copper rail called The Arc Runner runs from the biome's metal strip along the side of the arc chamber, sometimes angled and sometimes curved. We usually find a small pad on the top copper rail to protect against arcing and improve connection. Larger current devices usually have a double layer track when the contact arm opens the arc is formed between the fixed and moving contacts. the copper track widens the path leaving the ark far away the ark extends over an increasing distance to help weaken it a small ark will break and dissipate naturally as the path widens but a larger ark will continue on and hit the path camera.

The plates will split the arc into many smaller arcs that cannot support themselves or dissipate their energy. The Arc chamber absorbs heat and vents this through the top, we often find an extra layer of insulation around the chamber to help protect the housing, so why doesn't this 3 amp circuit breaker trip at 3 amps of current? This letter b means that we should look at the type B. table that is provided by the manufacturer normally we also find type C and type D and these have their own corresponding tables on the vertical axis we have the time and on the horizontal we have the current the section of the curve relates to the metal strip B for overcurrent protection the vertical section relates to the solenoid for short circuit protection.

The two lines show the minimum and maximum limits that the circuit breaker will tripwithin this area. At the bottom we have multiples of the device's rated current for simplicity, let's assume a 10 amp circuit breaker, so you have 10 amps 20 amps 30 amps Etc., if 20 amps pass through the breaker, that's twice as much. the rating, then we draw a line and see that it reaches the lower limit of the metal section of the biom and this happens at around 9 seconds and then it reaches the upper limit at around 50 seconds, so this should shoot between 9 and 50 seconds when 20 amps flow through the breaker at 1 times the rating, so 10 amps we see does not reach the line at all, therefore this breaker will not trip if 10 amps flows through it, it will not be it will trip until it reaches 1.13 times the rated current i.e. 11.3 amps and it will take 3600 seconds which is 1 hour with three times the rating say 30 amps it will take between 0.02 seconds and 11.5 seconds to shoot up, that is.

In the worst case, if 60 amps flow, it will take 0.01 seconds to trip, so type B breakers will trip instantly if three to five times the rated current flows through them or anything above that , but they will take longer if anything less than that happens. Types C and D will take much longer, therefore the tables are expanded, so a type C will not trip instantly unless 5 to 10 times the rated current flows through it and a type D will not trip will shoot up to 10 to 20 times the nominal value. So why would we want that? When an appliance is running it has a fairly constant current, but when we plug in or turn on an appliance we have an inrush current because the internal capacitors and inductors store energy and this causes a lot of current. to flow so for a split second we have a big current flowing and then it will normalize by the way our viewers can get 15% off all kiwe tools just use code em15 at checkout and I will leave you a link in the video description we need different switches for different applications and circuits, for example this induction motor may have a working current of 5 amps, but the input current is four times that of 20 amps and It only lasts 0.03 seconds, so we couldn't use a type B circuit breaker as it will trip every time the motor starts.

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