As a BSEE and PE engineer your explanation illustrating the connectivity and formulas are superb!!! I was able to figure out the line current and voltages of this transformer on these electrical dwgs. GREAT JOB

Dave I have a BSEE and PE license. Your instructions are so clear and simple for great refresh!! Thank you

If a consumer is supplied with two phases of 230VAC using 2 cables from a 3-phase 230VAC system with 3 cables, the current calculation for the two phases must account for the factor of √3.

note three, in table 450.3B allows where 125% does not correspond to a standard rating fuse or nonadjustable CB, a higher rating that does not exceed the next higher standard rating shall be permitted... however 240.21C Transformer Secondary Conductors does not permit 240.4B (round up rule)… so which one is correct? when can I and cant I round up for secondary side conductors? any feedback is much appreciated.

Prof Gordon is the best! thanks a lot!!

❤👏🏼👏🏼👏🏼

Thank you for making these great videos and explaining this so well!!!!

DAVE your a BEAST! Thanks for these videos!🙏

"Two Pi Fo Life" I laughed way to hard at this. I will never forget the inductive reactance formula now.

Thumbs up Dave! Keep up the great work!!

Sounds great, thank you.

This video came in clutch for my confusion

Can anyone point out the code that refers to the “calculated load” on the conductor. Sounds like as long as the calculated load isnt over the wire ampacity we can round up. But i dont see anywhere in 240.4 about the “calculated load”

Thank you

Scratching my head on the high leg... 240^2 plus 120^2 = Sqrt 72000 = 268.33... Trying to figure out how it's 208 with that analogy. But otherwise very helpful as I'm learning tranformer connections and where these voltages and configurations come from.

Dave, great video.

Great explanation! Thank you

Thanks a lot for this video. Sir.

Thank you Dave! You are the best

Teaching a class for electrical what materials were used for this demonstration please!

Funny you called it a “hot water heater”. A water heater doesn’t need to heat hot water lol

I really appreciate how you wrote it. It’s very understandle also what you said

when using a grounded centre tap voltage divider you get two phases 180 degrees out of phase, this is WHY it is called the Neutral, it is at the neutral point, 0V. so when current is being drawn on both hots, one is in the positive cycle and the other is in the negative cycle. being 180 degrees apart, where these waves meet on the neutral they cancel each other out proportionally. it is the ground on the neutral that is important, that is what keeps it at half voltage 120v on a 240v supply, if you lose the neutral point you just get 240V as at that point there is no voltage divider, if yo lose the ground / earth at the voltage divider you get a floating Neutral, which will move up and down the wave giving varying voltage depending on the loads on each side of the voltage divider. a higher current draw (higher resistance) will push the neutral up the wave giving a lower voltage to that side and a higher voltage to the other side up to the full wave and full voltage.

Ground fault devices are used to prevent current flowing to ground through a person like if you directly touched an exposed wire. They sure do work in other situations like the neutral touching the ground but that is not their intended purpose.

Excellent explanation!

Thanks for the video! This helped me identify and understand that I had a ground fault in my system that was leading to an overcurrent.

Very well explained!!

Someone please respond to me. Okay so over the weekend, precisely on Morning My client discovered that the extractor fan in his toilets got burnt, like burnt to the ground and because of that incident, his socket outlets were no longer working,his AC too, there was total black out on most of the lighting circuits while in some other circuit, the lights were just flickering. So I was called upon to troubleshoot what was wrong, my findings are as follows - there was current in all of the neutrals in the consumer unit - After isolating all the MCBs that controls the lights and leave every other MCB closed, the neutral no longer have current. - When I turn off the entire MCBs and turn on the Mains and read each bar connected to the MCBs with the neutral, everything is okay but immediately I turn on the identified MCBs introducing that current into the neutral line, then the readings are no longer accurate Note: I’ve checked the phases from the main incomer I.e RYB and also read them with the main incomer neutral . The readings are all perfect. PS.. Intermediate level.

Thank you for these wonderful videos. Please continue making them.

Excellent explanation! This is the best I’ve found.

One thing not clarified. Overload in a circuit breaker is a thermal activated opening of the contacts. A short circuit or ground fault is a magnetic activated opening of the contacts.

I really appreciate your video. My trade school is very expensive and the teaching sucks. You are helping me a lot

nice demo. Is this an open neutral or a lost neutral? Ive seen this referred to a lost neutral elsewhere.

This guy is goooood!!!

This dude was born to teach. His movements his voice his teaching method. 100 percent professional right here

The fallacy in this demonstration is that the voltage from one end of the secondary to the other is the DIFFERENCE and not the SUM of the voltages at both ends. If both ends were in phase and had the same voltage there would be zero volts between them. Moreover it is meaningless to use two different reference points in a circuit as your "zero" reference. This is not merely a matter of "perspective" but one of consistency.

Tanks for you❤😂

such a good explanation! hope these things was explained like this when i was at school :). thanks a lot for this video sir.

Dave! This is awsome! A was stuck in a loop trying to desifer 240.4(B)(2). You have helped a lot bro. God bless you in Christ. Best!

Great video, thank you!

I always compare pulse width modulation to a merry go round. When one person reaches out and grabs it and gives it a spin, he is applying a force for a very brief moment and then after some amount of time he is able to give it another spin. Each time he gives it a spin he is able to put rotating energy into it for a brief moment. Of course there are forces at play that want to slow the merry go round back down so energy has to be constantly fed into it to keep it going. Now imagine if there were a dozen people stationed around the merry go round and they could synchronize their movements perfectly so that there is always at least one person giving it a push. And that’s how it works. It’s short bursts of energy at a certain frequency.

In a furnace you have a 24 volt transformer usually rated at 40 va. A volt amp is almost the same thing as a watt. So 2 amps would be 48 volt amps (or close to it). Why do they use 3 amp (or sometimes 5 amp) fuses?

A lot of our buildings are supplied with only two phases but we run 3 phase equipment on them. Two phases on the pole and two transformers. The large transformer has a center tap neutral and the smaller transformer just puts out 120 volts. Every 3rd breaker is a high leg with respect to neutral. Do you have videos on this? I’m struggling to understand how a 3 phase compressor can run on this because it’s missing a phase and the rotating magnetic field is broken.

It’s the square root of 3 but I don’t know if that has anything to do with it.

Didnt write your units on the first parallel example... BZZZZZT WRONG ANSWER

I do have a question that I have been trying to wrap my head around for years and nobody can really explain it. When you have a 3 phase compressor connected to 3 phases, I do understand how there exists a rotating field and there is no need for a run capacitor. Here’s where I don’t understand how it works. How do you run that 3 phase compressor on two phases without single phasing it? Let me explain. A lot of buildings will have 2 transformers on the pole and they only bring two phases in. The larger transformer has a center tapped secondary just like a single phase house and the smaller transformer is just a 120 volt single phase transformer. Every third leg in the breaker box is a high leg. I understand how the voltages work out on this type of system but I do not understand how that compressor can run on these two phases without single phasing and without needing a run capacitor. The rotating field is broken.

You have it exactly right. I see this on videos and books and electricians don’t understand and everyone thinks legs and phases are the same thing. It’s always taught wrong. Either way you look at it, you have a single phase transformer. When we refer to phases and phase angles, we are referencing time. The phase angle represents the amount of time between something. With 3 phase power, each phase is really a separate voltage source that is regulated by the generators at the power company to be in sync with one another by an amount of time. When we say that reactive loads cause a phase angle between voltage and current we mean there is a difference in time between them because a capacitive circuit delays the voltage and an inductive circuit delays the current. There is nothing in a single phase transformer to cause any delay of any kind so the two legs cannot be “out of phase”.

So good

An electrician came to my house for work, and my light bulbs glow even when they are switched off. My inverter gets overloaded. My laptop speakers started making buzz noise. AC PCB got completely damaged. All my ceiling fans started deteriorating and ultimately they stopped working. 😡😭

Great video! Thank you