I was under the impression that the white wires were the safe ones. I was 19 years old up on a twelve foot ladder working in a commercial building. I was working the fluorescent lights hot because it was a problem shutting them off. So 10 feet off the ground I learned that the white wires are extremely dangerous. Fortunately I didn't fall or get injured. After that horrible shock from 277 volts, I was really having second thoughts about the trade I was getting started in. I'm a retired 68 year old electrician and by the grace of God, still able to talk about it.
Older guys (my gdads age) used the saying “only touch one wire at a time and you’ll be ok” which is absolutely untrue. A break in the circuit path neutral or hot is a place to get hurt.
dude, a grounded conductor only has zero volts until it is disconnected from the neutral bus. onces it is disconected the voltage increases to that of the ungrounded conductor, in your case 277 volts, when you touch that and then touch ground you become a big assed human resistor to ground. current flows......that hertz real bad.
Light bulbs ? All a light is -is resistance between to connections. It not matter voltage , lights still work on all volts. You can not test voltage by lights. Must be by a volt metter for volts or a amp probe for amps and a hertz counter for hertz. Hertz is very important , it the speed of the volts and watts on material by the second. Usa is 60 hertz per second as south east asia and asia and middle east is 50 hertz per second. It ok to run a transformer for 50 hertz per second in a 50 hertz per second area . But not run a 60 hertz tranformer in a 50 hertz area. The 50 hertz core is thicker than a 60 hertz core so the curent can move slower on the thicker core , but can not move to slow on the core that the core made for the size of hertz travels over it. The slower the travel equals the thicker the core must be so it not melt.
It would have been a little easier perhaps if the phase plots of the voltage sources were shown too. This would also help explain in 3 phase Y, that the neutral carries the delta current, and how by phase, each leg will return a portion of the others current.
The video seemed cut short a bit. Would have loved for you to spend a little more time on the flow in the neutral when you have unbalanced 120V loads between L1 and L2 and also touch on what would happen to the voltage of L1 and L2 if the neutral to the transformer was lost when the 120V loads were imbalanced. I know the answers, but would drive the point home while reiterating the importance of torquing conductors properly.
There was a house fire across the street from my house one time. The fire department cut power to the burning house and inadvertently opened the neutral to my house. The effect was expensive as I looked back and my house was very bright because of the unbalanced load now running through the lights. I lost a sump pump, a transformer controlling the thermostat for the furnace and a tv that night. This video is excellent and right on the mark. Any comments regarding getting shocked while working on a neutral are just moronic, what are you doing touching a circuit with the power on? You have no way of knowing if the 240 circuit is running balanced. You cannot touch a neutral with power on.
Bro you actually explain stuff so we’ll, and with your board drawing and explaining at the same time, It is VERY helpful for me Personally to understand Thanks just subscribed
Very awesome video.very educational for someone that knows a little about electricity but you really laid it out perfectly with your drawings.what a great lesson.keep the knowledge coming.👍
For non-linear loads like switching power supplies in computer labs, the loads will not balance, so there will be much higher neutral current then traditionally expected. There is a formula somewhere for calculating it.
I used to provide surge suppression equipment in the 80’s and ‘90s for large computer systems located in large facilities such as schools, industrial plants and skyscrapers. The loads can be balanced but that only works for perfect sine waves. But the switching power supplies used at the computer locations will introduce harmonics that do not cancel, rather they add to the current on the neutral wires. If you look on an O’scope, the voltage that left the power plant as a perfect sine wave turns into a square wave that is created at the switching power supply by creating odd harmonics (odd multiples of the pure 60 Hz sine wave). The practical solution was to actually DOUBLE the neutral wires to account for the adding, rather cancelling neutral current at the load. Such was the case for 120/208 3 phase wye panels that are usually the spot where 277/480 wye wiring is stepped down with a 120/208 isolation transformer, where the neutral is tied to the ground. Lightning can induce a 6,000 Volt, 3,000 amp pulse that while only lasting microseconds, is quite enough to fry any electronic equipment down line. You are especially vulnerable if you are at the end of a power feed, as the effect is DOUBLED as the wave goes down to the end of the line and bounces back upon itself towards the supply. This is why they generally don’t put transformers at the end of the power runs, but will extend the line several hundred feet past the last home or business drop. Most importantly DO NOT EVER do any wiring at your home or business… leave it to the licensed electricians who know what they are doing. Your building code may allow the owner to monkey with electrical service projects, but your insurance provider will not pay for an electrical system caused fire. And as an electrician once told me, 120/208 V can be forgiving, but 480 will not give you a second chance! Great video covering an extremely complex subject.
a neutral wire can carry an electrical current, especially when it's used as a return source for power. The neutral wire completes the circuit and provides a path for excess current to drain off in outlets or junctions. For example, the neutral conductor of feeders that supply systems with sine wave dimmers or phase-control is considered to be carrying current.
On a two wire circuit the neutral will be carrying the same current (amps) as the hot. The voltage on the neutral will be near zero, unless the path to the panel gets broken. If you shared a neutral on two 20 amp circuits that were connected to the same service leg in the panel the neutral would turn yellow and perhaps eventually cause a fire. The heat is caused by the current running through the wire.
Wow really good job man! Keep up the good work! Congrats on your accredation for continuing education. Maybe do a Journeyman's' Test Prep School and Contractors Test Prep school so these guys come out good. Thanks My biggest tip would be know where to find what in the Code book the fastest; since it's a timed test. I had my book all tabbed.
That was fantastic. I never had so comprehensive description of current flowing. But now I had much more questions: * single circuit have 2 fazes which are opposite to each other? 3 wires. * or it is actually 2 different circuits which are connected to 2 different home panels? 2 wires to each house, but it seems that 2 different neutrals will meet each other near the transformer. * here in Ukraine we have 240V circuit and hot and neutral 2 wires. ** Does it mean that we have x2 voltage through one hot wire ** or we have somehow combined opposite fazes in one? * also very interesting how 3 faze circuits are built to supply eg. machine in workshop
We've been around electricity for over 100yrs and we still don't agree on how it works. People stand on soap boxes and say this is the way it works and so it is taught and codes are written. I'm here to tell you that we were lied to. Juat a few years ago the building I worked in had to be completely rewired with wiring with an extra neutral wire because it was discovered that too much current was carried by the single wire and created a fire hazard.
One of the most impressive things to me about this video is that it takes 23 minutes to give the simple answer that is given in exactly one second between the (spoiler) 4:23 and 4:24 mark.
This is why the neutral wire doesn't need twice the current capacity of the individual legs. We might logically think that if we're drawing 20 amps on one leg and 20 amps on the other that we would read the sum (40 amps) on the neutral. The greatest possible current on the neutral leg is the theoretical point where one of the hot legs is fully loaded and the other has no load. At the point where both hot legs are fully loaded, the current on the neutral is theoretically zero.
At 12:34 is when all of my knowledge of balanced 3 phase loads came in and it clicked for me as to why the neutral sometimes does and doesn’t have current flow. 😁
Even with a balanced load the current is still flowing through the neutral. You explained that with the 10 amp -2 amp=8 amp explanation. You measured 8 amps because 2 amps canceled due to the "out of phase" condition. If you have a balanced load the same thing applies. 2 amps cancels 2 amps because they are out of phase. It is a meter issue. The current is still flowing through the neutral, but an ammeter is incapable of measuring it because it is out of phase. For measurement purposes, the phases cancel each other, but the current is still flowing through the neutral.
If there is no current flow in white neutral, why would all that extra copper wire be needed ? Only time neutral is needed but not used is if hot has found a sneak circuit, short, arc to ground, then ground is carrying dangerous circuit return current. Although white neutral and ground are tied together at service entrance, only white neutral is suppose to carry circuit return current.
Great content Dustin! As an electronics instructor and evaluator for over 30 years your enthusiasm is awesome! Let me pass along a few tips that might help: 1. Your rate of delivery is way too fast. Slow down. This was a 23 minute video. 30 minutes with the same content would have been much easier for most people to grasp. 2. Your sequence of illustrations was poor. You should have started with a single circuit, then double circuit, then a balanced split phase, then an unbalanced split phase. 3. Your equations were presented backwards when doing the math. I = V/R You presented I/R = then showed V/R. 4. You should have made it clear that these were resistive loads, not reactive which are very different and that they would be covered in another segment. 5. Use the standard: Tell 'em what your gonna tell 'em, Tell 'em, Tell 'em what you told 'em approach. Much better learning happens that way. 6. Your panel drawing tried to show WAY too much and was hugely confusing. Redraw as needed. 7. A physical example on an actual panel would have helped a lot of learners and would have dramatically simplified your explanations. 8. Pre-drawn slides posted on your white board would have been great, then use the whiteboard to highlight what you are talking about.
Most of this is awesome. If you have a 3 phase source, then each phase is 120 deg out of phase (120x3 = 360). If the installation has 2x phases then in fact there will be the residual of the 3rd absent phase flowing through the neutral (normally tied to earth in Australia, not sure on the practice in US). What would be interesting is the same diagram and explanation for a single phase installation (which is what all domestic connections are in Australia - a single live phase, neutral - to where? - and an earth).
Not trying to nitpick and you probably know this. Residential 240 is single phase. Referring to phases is not technically correct although I hear it all the time. Instead of phase or phases I’ll refer to Line 1/2 or simply hot conductors.
I know exactly what you mean but have no trouble at all with hearing the 120V lines referred to as “phases,” even though derived from single-phase 240V. Nitpicking is what a complaint about the terminology is, because it is useful to view the 120V circuits as a 2-phase system. There are some other terms which some people use to describe electric circuits which are less useful and more confusing, so worth complaining about.
If no current is flowing on the neutral of a 120v circuit with a load, you should turn off the circuit breaker. Then check on grandpa. All kidding aside, we can be thankful for the advent of 2-circuit "romex" cable that actually has a separate neutral for each "hot" conductor. (Notice I didn't say "phase" conductor.) This new cable is identified as 14-4 and 12-4 or 14/2/2 and 12/2/2, which consists of a black conductor, a white with black strip conductor, a red conductor and a white with red strip conductor. This new cable is very compact, and appears to be no larger than a 14/3 or a 12/3. This eliminates the need for a shared neutral in a dwelling, but here are a couple of other benefits: 1) Want to run both circuits in the cable on the same phase? No problem! 2) How about using AFCI/GFCI breakers in the panel on two remote circuits? Now you can do this with one cable!
voltage in a series circuit is divided between loads while the ampere or current remains the same across both; ohms law. and voltage in a parallel circuit remains the same while the amperes or current is divided.
If reading amps on neutral which is needed to balance 3 phase systems is always the miss Ballance between the hots,,,, if one crews up a 3 phase service in a large scale senario one can have very heavy neutral load,, and then one has to move loads around from bus to bus, to balance the load ,,, and the go threw and make sure all motors and such are still running correct direction 👍
YES it does on a single phase circuit what goes to the load in the "hot" returns to the source in the Neutral conductor! Never confuse a Neutral with a Ground!
The Union apprenticeship doesn't charge you any money for education. Plus they guarantee you a job while you're learning, paid living wages, and paid benefits. Journeyman wage currently in Las Vegas is $50.48 an hr. That doesn't include the benefits and retirement the contractor is required to pay you for per contract. Non Union charge general contractors a high number for an employee and pay them low with a tap on the back. No pension or Healthcare paid for with a low wage.
Electrician U the light marker colors don't show up on your board. yellow shows up a bit (squint), white does not show up at all. Kind of hard to follow.
I wish someone could answer if current flies back to the pole while operating a generator with the interlock approach. Since neutral is not disconnected can this be an issue for lineman or any thing else?
It is the usual practice when making electrical schematics and describing the function of the circuit to start at the hot wire and finish at the neutral and call it the return. However, as we we know that is not strictly correct but it serves our purpose to have a start and finish to a circuit. Some people can get carried away when describing circuitry but a common sense approach should prevail. Please explain what you mean by “giving resistance to the hot”.
@@kennethcohan9630 well I guess for instructor s I should have said "Giving resistance from the hot through any fixture turned on. If you're not familiar troubleshooting residential and commercial problems. For an example open a hot circuit feeding an appliance turned on. Hopefully low load. When you open the neutral at the panel you'll see a small spark. Then measure the voltage between the open neutral and the panel neutral buss. Depending what voltage you have. You should read half voltage like an open neutral. Then connect the neutral back up and you should measure a small amount of current this return. Sorry I miss spoke.
Nice tutorial👍. I have a question: When the furnace comes on, the lights in the house flickers, and I lose power to the master bedroom, sometimes 2nd bedroom and the living room. I've tested every single block/breaker and received 123-125. Is there anything I can check or something I can do before spending $400 for an electrician to come out?
A neutral is a travelier not a ground. Think what does ac mean ? Aleternating curent. Alternate mean goes out and returns. If circuit is 120 v - 20 amp , it 120 v 10 amps back= it returns 1/2 of curent back to service. Ac .
My question is what is the meter measuring? If it is measuring the field, it seems that would be why the fields are cancelling and the meter says zero. Is the meter measuring the actual current moving? I have my doubts; is the meter "in" the circuit or outside measuring the field(s) created by the movement of the electrons?
Yes, current flows on the "neutral" and because of that, "neutral" is a wrong, bad name for it. I call it "return", which still isn't accurate in terms of physics, but at least it doesn't imply you won't get zapped by it under the right conditions like "neutral" does.
“Return” is an inaccurate term so has its own pitfalls. “Neutral” means that it is near ground potential under normal conditions. Of course anyone working with electricity should be prepared for abnormal conditions. People get confused when they don’t have a good grasp of the difference between voltage and current. When you get a shock from a white wire, it probably isn’t connected to the neutral bus bar in the main panel. When you disconnect a wire from the neutral bus bar, it is no longer a neutral.
There was a lot of good information in this video but there was also some confusing information in this video that I think should be clarified if it’s going to be used as a teaching tool. And I did notice that you made an effort at one point to attempt to address the subject but I just didn’t feel it was very clear if a person who did not already have a basic grasp. I in a 240/120 split phase topology The reason for having the neutral is in order to be able to have 120 V devices. Without it there it’s not possible for you to have 120 V potential. If all you wanted to run was 240 V loads there would be no need for you to have a neutral conductor because you could simply have the two hot conductors which are tapped off the end windings of the transformer and fed down to the entry point of the dwelling… And that would provide you a potential of 240 V tap to tap. That would happily run anything like a stove or a dryer without a problem. However, when you wanted to have a regular lightbulb or a hairdryer or something of that nature you to have an issue because when you’re missing the neutral, which is connected to the center tab of the transformer you don’t have that 50% potential available to provide you that 120 V that you need for those smaller residential devices. I when you have a 240 V load I you can actually have the opposite hot conductor function is the neutral in the off cycle, since this is a sea power and you’re constantly having a 60 cycle waveform to take advantage of with one tap of that transformer at the bottom side of that wave form and the other top of the transformer at the top side of that waveform. When your meter does indicate current flowing on the neutral with a clamp on device what that does indicate is an imbalance of how you have your 120 V circuits loaded into your panel. That doesn’t mean it has to be perfect but if you see a lot of current you may want to re-organize how you have the breakers configured.
Electricity nerds like myself will be quick you point out the difference between the simplified model you teach and the real word physics - but I think explaining it this way makes a lot of intuitive sense and for the electricians application is probably the best way to learn. There are certainly instances where neutral wires don't carry current, and they'll even be designed out of systems where not necessary. This is almost exclusively for balanced three phase load applications though, that you won't see very often in the field working with branch circuits and power panel distribution. Neutral current is even further exaggerated when your loads have complex-power phase shifts so you not only need to match real power P but reactive power Q of your loads.
the only time there will be zero current in the common part of the neutral line is when the current in each of the 180 deg phase sides of the panel have exactly the same but out of phase currents, if the currents are not identical as will be the case most of the time there will be some current in the common neutral line its so cute when "electricians" try to explain electricity as opposed to the physics department of a university electricity and magnetism is among the hardest physics classes and if you don't have pretty strong understanding of calculous you can not understand electricity other than extreme simplifications your circuit is correct, your electric field stuff is not very correct and the real answer about current in the neutral is there can be zero current and there may not be
Despite the difficulty of electricity from the viewpoint of physicists, practical electricity is so easy that a lot of people learn it in their teens, before ever studying physics or calculus.
Easy test....remove some insulation from the neutral on .....let's say a drill. Plug the drill in to an outlet and pinch the bare wire on the neutral. No shock!! Now ......pull the trigger on the drill...OUCH!
Ground is missing and it's tied to the neutral so zero flow is expected. Also phases are not always 180 out and of course loads aren't balanced. Good presentation but the assumptions ? -MG
Ive never been shocked from cutting or touching a nuetral wire. I must have not been grounded or completed the circuit but i have seen a neutral wire arc while connecting it live to the neutral buss bar. Also I've seen many electric panels with Neutral and ground connected to the same buss bar and the ground wires dont have voltage. So im guessing it wasnt showing voltage because it wasnt completing a circuit with the ground making it a dead wire. Can you give me even more clarity. Is my asumption correct?
Answer a question for me. 🤔 I've notice that my house has several neutrals tied together that are fed from different breakers. So what you're saying is that even with breaker A turned off, current from breaker B could flow back on neutral A which is bonded to neutral B. How dangerous is this?
Another completely unrelated electrical fact that is going to surprise and maybe even piss a couple people off. Your electrical devices are not powered by the current flowing through the wires in your cables, it is actually being powered by the electromagnetic field surrounding the conductors that is created as a byproduct of electron exchange. This was found out to be the case when a cable was being run under the ocean. The insulation and sheathing on the cable was too thick and didn't allow the electromagnetic field to be created outside of the insulated conductor, so the cable was rendered useless. It is the same reason why a light bulb sometimes will illuminate before making contact with anything. The electromagnetic field stays both inside and very close to the surface area of the conductor.
When measuring current on the neutral wire because of the the loads are unbalanced and you got unbalanced current is in this called residual current or leakage current and how do you prevent leakage current and residual current on the neutral line?
lol you just shoe horned in the real kicker at the very end. for anybody just wanting an answer: yes, current flows in the neutral back to the transformer IF the loads are unbalanced. otherwise, no, they just oscillate back and forth through the hot and neutral across the different phases.
I have no idea what this guy is talking about he talks so fast my head id whirring! Thank goodness I got my degree in rocket science and not house wiring!
Great video, I have a Chinese Solar Hybrid 5KVA 230v 93A One Phase Inverter 48v charge controller I live in the US 120v Breaker Box 100A , investing the 230v is 115v on the Hot Line & the Neutral has 115v = 230v You are the expert would that also mean the Amperage is 46.5A per line ? “ want to for Emergency Power only DIY he hot line to L1 & the Neutral to L2 giving me One Phase in my complete breaker box. I do not. Have any 220v lines in my house I have gas for heat And cooking!
9:04 this doesn't to me. What if you have one light bulb on the circuit? You basically invented another lightbulb to say that they're "pushing and pulling and canceling each other out". What if there is only one breaker, with one lightbulb? Do you get voltage on the neutral at the bus bar or not?
Wait till you get to the Neutral line in a 3 phase circuit and "Why don't Hydro towers carrying 715 Kv have a Neutral "I count 3 live ones unless you count thoise little support cables or the Earth.
I understand the utility of explanations in terms of current flow as electrons moving through a medium, but none of it is true. This only causes people's minds to be blown when they learn about Poynting vectors, how power travels from source to load over both paths, that any net travel of electrons is very slow and in the opposite direction, and again over both paths. It's only then that AC and DC both make sense, since regardless of the phase (or lack thereof) power is always delivered from source to load. It's all about the fields! To state it another way, the power company is not producing electrons that are being pushed out to you and need to be returned back. The whole push-pull idea is simply false.
Bottom line how do I correct this ? I was replacing a receptacle and turn the circuit off, I tested the black wire and there was no electricity, but, when I started unscrewing one neutral wire sparked, with the tester I saw that there was some current, not much but some, help.
Back in my first year of apprenticing I was working with a journeyman who sent me to find an open neutral in a junction under the house and when I found it and asked him to turn it off he said what do I gotta turn it off for you’re just fixing the neutral connection…trusting him I started pulling on the connections and got a nice zinger.
Voltage is not the same as current. If you have an open neutral it is no longer a 0 volts wire. It's now energized to 120 because there's no path back. At which point it's technically not a neutral. Anytime you touch a wire under load that has current running through it, if there's less resistance through your body to ground than there is in the wire you will get a shock.
For what's it worth, I actuallty liked that you didn't have the "schematic" drawn already. Not sure why, I have seen you draws these dozens of times, I guess it just gives me time to process it things and get my mind in the right frame for what you're about to discuss.
I am a senior technician, self-employed in the PCB manufacturing industry. Back when I was struggling with the difference between ground and neutral, I came up with an analogy using water that helped me better understand. Imagine you had an upstairs laundry room. Of course, there would be a drain in the middle of the floor just in case the washing machine sprung a leak. But, in normal use, the water in the washing machine would go down the intended path through the drain behind the machine. The drain in the floor acts the same as a ground. It's not an active part of the washing machine plumbing but if necessary it can carry the water away to avoid flooding the downstairs. The drain behind the machine acts as the neutral because it is intended to carry the water away in normal operation.
I wish all electrical tradesman were as cool and down to earth as this guy and willing to teach... I would've learned so, much faster and much sooner in my career.
This is probably one of my favorite videos you've done. Good job! I liked how you got into the more scientific way of explaining your point, but keeping it simple enough for the beginners and apprentices. Keep up the good work. Thumbs up!
I knew the answer, but watched anyway because I like your teaching style and enjoy watching. A topic you may want to consider is (for the general public) how to select the proper size generator or inverter to meet grid down needs. I find myself giving the same advice in comments over and over, and would rather just refer them to a good vid.
I also knew the answer and i'm from Australia so i figured i'd watch to see if he gave the correct answer as so many sparkies in Australia fail to understand these fundamentals I agree, overall he did a good job
This would be a helluva lot simpler if you just show the two wave forms on a graph. The user could see that the troughs intersect at zero, and the peaks are the same magnitude and different polarity. This graphically shows the math, which equals zero along the whole line.
I was kinda thinking the same thing. I'm only halfway through the vid, so maybe he addresses it better but it seems like showing the pushing/pulling that the two balanced loads are doing, resulting in no net change in electrons in the neutral bar, would better explain why there's no current on the neutral.
If the neutral is balanced (cancelling out), does the current flow across the other hot wire? That's what I thought he was showing but I'm not sure about the bulbs becoming a part of a 240v circuit etc ...
This is absolutely incredible, I remember watching this 3-4 years ago just out of curiosity for the trade. Seeing this channel grow and continue to educate is amazing, I really appreciate the time and effort put into this. I’m a chef, not even an electrician and I watch most of these videos.. so thank you!
I was a chef for 20yrs, then covid happened, went on furlough, did a little off the books landscaping to supplement UI.. Now I’ve been an apprentice electrician for a year and already make about an the same as the most I ever made cooking. And I have a lot of weekends off now😁 At a small-ish company doing commercial and industrial only, I can definitely say on average this trade is far less physically and mentally draining than cooking. And the money is sooooo much better. There’s a shortage of electrical workers nationwide. Just putting that out there. Sometimes I miss the kitchen but overall I’d say switching to this trade is the best career decision I’ve ever made
I been watching your vids since I was an apprentice and they helped me a lot to get my Journeyman’s card. Now I’m on my way to get my masters and I’m sure I’ll pass it.
I would agree with you for apprentices and people new to the trade for people with experience most of his topics are as basic as they get like 1st year stuff
Dustin is so good that one of my teachers in my trade school just used his videos to fill up the entire class period on Zoom. Maybe because he was lazy, who knows but the fact that these videos are so educational and informative that they can be used as real in-class school material is amazing and shows its quality and value haha.
For me, the way he talks is like he is talking to a friend rather than a superior. He is able to maintain the attention of the younger generation and keep things interesting.
Sounds like most trade schools. They suck. Most are filled with instructors who are looking for a little extra cash and don’t really care about the student. People like this guy and myself actually care about educating the trade one student at a time.
Sounds like a lazy teacher, you pay to be taught, the video should be homework, & review, & expand on in class! The video should be used as a supplement and watched on your own time, very lazy teacher! But yes his lessons are very good
Really an excellent explanation! Important to understand for multi-wire branch circuits as an explanation of why the hots need to be on different phases.
You should do a video on 240v circuits that don’t use a neutral. For instance a well pump. How it doesn’t need a neutral because it’s 240v only. That’s something that took me a minute to wrap my head around as I was learning.
And then there's devices that use 2 phases, a neutral, and a ground, like electric dryers! The heating element is powered by the 240v, but because the socket provides neutral, things like light bulbs that illuminate inside when the door is open can be normal 120v bulbs because it just grabs power from one phase and neutral.
@@Lierofox it’s kind of silly that a lot of dryers also require a neutral. If some of the controls and control illumination/screens require 120v, they could engineer the dryer with a control power transformer inside to get 120v control power off the supplied 240v circuit.
We had fires in our office cubicle walls back in the 1990s due to excess neutral wire current. The cubicle outlets were spread among three 120V phases with a shared neutral wire. We all got office computers that had non-linear power supplies: their AC inputs were bridge rectifiers feeding big capacitors. AC input current only flows in spikes on the peaks of the AC voltage to charge the capacitors. In a 3 phase configuration with balanced resistive loads, there is zero neutral current; the current flows (push and pull) cancel. In our configuration, the current spikes on the AC voltage peaks occurred 120 degrees apart, so there was no cancellation. The neutral wires were overloaded and caught fire. Facilities opened up the circuit breaker panels and used an infrared scope to look at the neutral wires to find the ones that were hot. They then ran new dedicated circuits to feed the computers on those wires.
Nonlinear devices (power supplies, VFDs, and others) contribute harmonic distortion onto a power distribution system. Certain orders of harmonics called triplens (includes the 3rd, 9th, and others) do not cancel out even in a balanced three-phase system. Triplens specifically sum on the neutral. A three-phase system with a large percentage of nonlinear loads (depending upon the type of course) may see triplens. Where applicable, this means more heating on the neutral which is even worse the more unbalanced a three-phase system becomes due to connected single-phase loads. Assuming no other means of mitigation is employed, a smart engineer will oversize a neutral for this reason (perhaps 150% or even 200% compared to the phase conductors). This is also a reason to specify a distribution transformer with a K-factor rating that is selected considering the total percentage of nonlinear loads.
As a practical point to novices doing wiring. Of course whenever possible turn the power off before connecting wires. But remember if you touch between two neutrals you can become a load. In effect you put your body in series with that circuit path. So the assumption that some people have that "the white wires are safe" is bs.
Don that is so true! When I was a lineman guys would get careless handling neutrals, especially during storm trouble. Get yourself between an open neutral or a tool between an open neutral and you can find out the hard way.
I don't know the NEC codes of today, but I recall an old tale of a plumber being electrocuted working on a water meter because the main neutral was bonded to the house side of the water pipe and not the street side. True story? I have no clue.
I thought the electrons didn't so much flow through the medium as vibrated back and forth and it was the electro-magnetic field that delivered the current to the load.
I think when electricity is taught it is treated like the flow of water as a basic understanding. A physicist has a deeper understanding of magnetic fields etc.
@@fornife5004 Yes, precisely. Molecules of water leaving the pump outlet, traveling through the closed loop, and then returning to the pump inlet. It's a good analogy for a mental picture and for basic understanding. But, it's only an analogy..
Fun Fact, the balance and cancellation phenomenon is used in Pro Audio to neutralize electromagnetic interference on XLR audio cables. They're "Balanced" so that what you hear after amplification is actually the imbalance. If you plug a stereo audio feed into an amp through a balanced connection, you instantly get a karaoke track, since the instruments are rarely centered on the feed, but the main vocals are - the voices just "disappear". If you've ever had issue with the audio feed on a RU-vid video and others report it is fine, you are hearing the digital version of this.
Though you’re on the right track, that’s not entirely true. This would only occur if identical doubles of the vocal track were 180° out of phase, panned hard left and right and summed to mono. But the principal that, similarly to electricity, speakers are incapable of pushing and pulling at the same time.
No, if L and R are identical, i.e. voice in the middle, L minus R will completely cancel the vocal and anything else that's fully centered. Discovered this when I was 10 when I connected each speaker's minus wires of our stereo system together but not to the speaker ground. It was so cool to hear the instrumental version of my favorite records. Now they put a lot of stereo reverb making full voice removal harder to achieve unless you use AI techniques.
