a fun one

[billdozier]

Hey guys in an earlier post I started to look at non linear loads vs linear loads. Im somewhat understanding the definition of these two. My question than becomes harmonics. I remember vividly as a greenie a pipe that had a wire, for the best iliustration playing a beat in it. Is this caused typically by undersized neutrals or is there another factor involved in this scenario. As in 310.15(4)Thanks again. To the moderators if this needs to be moved I understand why.

 

[charlie b]

Sorry, but I do not understand the question. I'm not even sure a question was asked. What do you mean, ". . . playing a beat in it" ?

I will say that the size of the neutral wire has nothing to do with the cause of harmonic currents. Size will impact the ability of the neutral wire to carry the harmonic currents imposed upon it, without overheating the wire. But the cause of harmonic currents comes most often from the loads, and sometimes from the power source.

 

[al hildenbrand]

I remember vividly as a greenie a pipe that had a wire, for the best iliustration playing a beat in it.

I think this is a conductor inside a conduit that is being moved by the unbalanced magnetic fields present inside the conduit.

Is this caused typically by undersized neutrals or is there another factor involved in this scenario.

I agree with Charlie, that the loads and sources are the cause of harmonics.

In the textbook ideal electrical circuit, the source provides a perfect sine wave of voltage and current. A simple resistive load, such as an electric heat element, will draw the current in a perfect sine wave. There are no harmonics in such a circuit.

Harmonics appear when the load draws the current in some waveform different than a perfect sine wave.

 

[billdozier]

by playing a beat it was being moved by the unbalanced magnetic loads inside the conduit. It was constantly hitting against the conduit. I guess what I should of asked is what causes the movement of the conducter? Apparently the loads play some part in this due to sine waves. And how can it be avoided? Sorry for the confusion.

 

[76nemo]

by playing a beat it was being moved by the unbalanced magnetic loads inside the conduit. It was constantly hitting against the conduit. I guess what I should of asked is what causes the movement of the conducter? Apparently the loads play some part in this due to sine waves. And how can it be avoided? Sorry for the confusion.

Are you sure this wasn't from initial inrush from a larger load??? Are you saying this was constant?

 

[billdozier]

yes nemo if I remember correctly it was constant. We were there to troubleshoot but I got pulled off to fix other problems

 

[physis]

You're talking about reactive loads. Inductance and capacitance causes a phase shift that has to be calculated with the simply resistive component of the circuit to put a value on it.

It's a somewhat complicated subject. I'm not sure if you can just get it a little bit and apply it in a practical sense.

A simple resistive load, such as an electric heat element, will draw the current in a perfect sine wave. There are no harmonics in such a circuit.

You have to be careful with these heating element type things. Many eons ago we had built a load bank using five simple ol wirewound resistors. At 3/4 load or higher when the cut off relay disconnected the load the relay contacts would arc indefintely. We finally destroyed a resister and found the resistive wire had a mild curl, to get more resistance in a shorter component, and was also wrapped around the ceramic core. We didn't bother to measure it but judging by the arcing these things had a more than merely significant inductance. The inductance value was not mentioned on the resistors specs.

 

[physis]

by playing a beat it was being moved by the unbalanced magnetic loads inside the conduit. It was constantly hitting against the conduit. I guess what I should of asked is what causes the movement of the conducter? Apparently the loads play some part in this due to sine waves. And how can it be avoided? Sorry for the confusion.

Sorry if my last post seems a bit out of context, all of sudden there's a bunch of new posts.

Let me ask you a couple things about "hitting against the conduit".

Was it a constant pulse, I mean the time between noises always the same?

And, if so, what do you figure the frequency was?