Comments by "GH1618" (@GH-oi2jf) on "The Engineering Mindset" channel.

  1.  @EngineeringMindset  — That’s a better animation. Thank you.
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  2. It isn’t a particularly good way to describe it, so most people don’t use that model.
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  3. Copper is anomolous. The stable configuration is actually …3d10 4s1.
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  4. The frequency is unrelated to the voltage. In North America we use 60 Hz because it was found to provide the best balance of efficiency and practicality whan the AC power system was developed by Westinghouse. European countries use 50 Hz because they don’t like the number 60 (it being unmetric-like). They couldn’t do 100 Hz for practical reasons, so they chose 50 Hz (which gives 100 half-cycles).
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  5.  @csp405  — wrong
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  6.  @BrianSmith-xs1yo  — Don’t mess with the hot wires like that! The neutral conductor is the one tied to ground. It is always the neutral, whether current is present or not. The hot wires are always “hot” although they might be switched off.
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  7. The transformer pictured at 1:18 is a delta-to-wye. The local distribution network in N. America is generally 3-phase wye, with the neutral running from the substation to all customers. The transformer at 2:04 is a single-phase pole-mounted transformer that produces the split-phase power for customer use. The primary is connected to one of the distribution phases and neutral. It isn’t shown here, but the neutrals on both sides of the pole transformer are bonded and grounded.
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  8. What do you mean “neutral is not neutral”? The neutral part of the circuit is connected to ground at the panel and the center tap of the secondary should also be connected to ground at the pole. The neutral wires should be at ground potential under normal circumstances.
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  9.  @eduardojreis  — Correct, the center tap of the secondary is the “neutral.” The neutral is grounded. The lines L1 (A) and L2 (C) cannot be connected to ground. They are connected to the loads through sockets and plugs. Electrons flow when there is a circuit from the transformer secondary through a load and back.
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  10. Consult the codes and take your plan to your electrical inspector for approval.
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  11. Yes, “source” is a confusing term. By convention we ground the center tap of the transformer and call that “neutral.” From the standpoint of the circuit, the hot and neutral wires are equivalent. From the standpoint of a person standing on the ground, the hot wire is the one that will give you a shock if you touch it.
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  12. They just put them where they need them.
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  13. Yes.
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  14. It’s easy. The neutral is tied to ground; the hot is not. That’s all there is to it.
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  15. security camera — No, he is not writing about 3-phase here.
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  16. mgoblue — Looking at the hot connections with respect to the neutral, they are 180° out of phase.
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  17. security camera — Yes, but 3-phase is not the subject of this video. Discussing jt here just adds confusion.
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  18. security camera — In apartment buildings that might be the case, because they might want 3-phase for motors.
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  19. There is no fixed positive and negative in AC. In illustrations with batteries, he uses electron flow rather than conventional current. It doesn’t matter, really. Better to skip that part, in my opinion.
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  20.  @csp405  — Ohm’s law. Ampetes = Volts / Ohms. The resistance is 0.5 Ohms because two identical loads in parallel have half the resistance of one load.
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  21. No. “Neutral” is the center tap of the transformer secondary.
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  22. Every electric power distribution system has transformers. What do you mean by “bipolar power supply”?
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  23.  @_-BIMBO-_  — It is likely true that we have more transformers, but they are not on every pole. In residential areas, one transformer will usually serve two or three homes. In commercial areas, the transformer will often be underground and serve one building. I expect you have more low voltage substations, though. In the US, a single local substation can supply a small town. I just looked at some data on European power distribution suggesting that about 100 low voltage customers per substation was typical. Our final substations can support a few thousand customers because they distribute medium voltage throughout their service area, then convert to service voltage near the point of use.
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  24. We (in the USA) have countless devices which work perfectly well on 120V. Customers who actually need 3-phase power and higher voltages can get them.
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  25. “Hot” means that there is a significant electric potential relative to ground. You will get a shock if you touch it and provide a path to ground. “Neutral” is a conductor held at ground potential. Both hot and neutral wires are current carriers.
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  26. firpofutbol — In the USA, we do require fault detection for new circuits. We do not require people to update their old systems if they are operating correctly. There are two reasons for this. 1. The cost would be a burden for many people. 2. We don’t like coercion in the United States. We encourage people to make their homs safer.
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  27. Most houses were built berore GFCI existed, and more were built before GFCI was required. In the US, we generally enforce new codes only when new work is done.
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  28. Parallel resistance is like adding another driving lane to a road. There is more room to carry traffic.
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  29. All of North America uses this system.
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  30. Kelly Brown — It’s a metaphor. Current is not exactly like water flowing in a pipe, but it is a useful analogy. When working with electrical circuits at this level, it is not necessary to understand electrons the way a physicist understands them. You can obtain a practical understanding of electricity without understanding atomic physics.
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  31. Gerald Foster — It is better to not get hung up on the physics when studying electric power, especially for AC.
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  32. Ken McCandless — I can’t believe many people will give up their terminology for NEC terminology, especially since the three NEC terms are so similar. EE Times noted that mistakes have been made because of the poor nomenclature.
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  33. Electricity does not choose just one path or the other. It follows all paths, dividing in proportion to the conductance. If you are standing on damp ground and touch a hot wire, enough current will be conducted to do serios damage. It is best not to test this proposition.
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  34. AC allows a transformer to be made because the principle of a transformer is that a moving magnetic field induces a current in a conductor. A steady DC has a stationary magnetic field around the conductor. Once you have a transformer you can make high voltage. High voltage will transfer a given level of power with fewer Amperes than a low voltage. Fewer Amperes means lower losses in the transmission lines, and smaller wires in the transmission lines. If you exceed the current carrying capacity of a wire it will heat up and melt, like a fuse. In short, high voltage allows the transmission of large amounts of power over wires. Another factor is that AC can be transmitted in three phases over three wires in a delta configuration. Twice the power can be transmitted with three wires instead of two.
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  35. A ground fault is current leaking from the hot wire to ground. For example, if you touch the hot wire, you will provide a path to ground for current. A GFCI will detect that the current in the circuit is unbalanced, and will trip. An arc fault is current leaking from the hot wire to the neutral in the same circuit, but in an amount not great enough to cause an overcurrent trip of the breaker. Or it could be an arc within the circuit at a loose connection. An arc between the wires won’t unbalance the circuit like a ground fault, but can start a fire, so is dangerous. An AFCI detects arcing, but I don’t know how.
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  36. What does “looped with” mean? The neutral is tied to Earth, so everywhere in the neutral part of the circuit the potential to Earth should be low.
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  37. yes
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  38. The utility company just needs to provide a transformer and wires capable of carrying the current. It will be 240v regardless. You can’t just replace your box without checking with the power company, because if the drop is not sufficient for your load, it could overheat. An electrician will take care of everything. I have installed a load center once myself. I would not do it again.
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  39. It would be best to have a subpanel in the outbuilding, but it doesn’t need to be a large one.
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  40. This is incorrect.
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  41. probably
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  42. Everybody calls it neutral.
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  43.  @3328music  — Sure, but the vernacular is not determined by official documents.
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  44. For one thing, you couldn’t tell when you have a ground fault.
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  45. The field is stronger in the hot wires.
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  46. Electricity will move as needed to equalize the charge. To start with a simple example, if the current path contains two resistors in parallel, the current will go through both, but will be divided in inverse proportion to the resistance. This can be generalized to any number of resistors. In a power distribution system, the neutral wire is a low resistance path back to the transformer — much lower than the path through the earth. Some current would flow through the ground path, but it would be insignificant.
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  47. kunal patil — Please give a time indication.
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  48. Harry Parkinson — In part, it is. In North America, in dwelling units, in some jurisdictions, voltage to ground at a receptacle is limited to 150V. Higher voltage might be permitted for permanently wired fixtures. That is purely a safety rule.
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  49. In this system, the neutral is held at ground potential. It is grounded at the pole and at the main service panel (or first cutoff, which might be at the meter). That is done so the hot wires are only 120v from ground.
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  50. Heshy Meschy — If we did “convert” to 3-phase it would have to be 208Y/120V, which we already have and which is compatible with our existing devices and our codes. Any system we use has to support 120V devices because we have billions of them. Converting to 208 would mean that 240V heating devices would be operating at reduced power, so there is no demend for that in residences. The market for 3-phase is for customers who have a shop with a lot of motors. Such a customer could have 208Y/120V in the shop and 240/120V 3-wire in the dwelling. Nobody is asking for 3-phase in dwelling units because there is no point to it.
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