Just to clarify.

[mivey]

...Absolutely no guarantee these numbers have any resemblance to accurate calculations. :-? Didn't check the equations, didn't check the entry, didn't check the math...

Well, unless we both are wrong, you are correct. I only solved for the loop currents. I divided by 120 to compare with yours:

[editX2: I checked the source currents and I get Source i1 = 0.367(same) Source i2,i5 = 0.325(same) Source i7,i8 = 0.558 (same) and
source i9 = 0.433 (same). It would appear the loop magnitudes were correct AND the sign was correct...I'll get it right one day. It was for fun anyway. ]

 

[rattus]

What diversion?

What diversion?

An example was requested, and I provided one.

Now, we don't need to solve this mess to see that the choice of voltages, resistances, and phase angles can cause some of the source currents to be backwards so to speak. That is the point that was raised a day or so ago.

 

[coulter]

Well, unless we both are wrong, you are correct. ...

Well, I'm flat amazed that we both got it wrong:grin:

Okay, I'm not amazed you got it right, I'm amazed I got the equations correct (my coefficients look the same as yours - with the exception of a minus sign or two) and all the numbers punched in right.

I'm also somewhat supprised I picked all positive current flows by eyeball.

carl

Got to stop - my shoulder hurts from patting myself on the back:roll:

 

[coulter]

An example was requested, and I provided one. ...

Nope. Doesn't fit the requests. From Post 193:

rattus -
I'm okay with the math being able to be worked out regardless of the chosen direction for a KCL loop current. I'm still not clear on why one would want to pick out a current direct different than that matching with the voltage sources. I'm also not clear on this phase shift at the currents pass through the N point. I Perhaps it would be more accurate to say I don't understand why anyone would ever want set up for a solution to do it

I'm with mivey, I think a real world problem illustrating why one would pick this orientation will help. But don't use a text problem. Pick something you have worked on in the last year or two (or ten) - or even a current problem not yet solved.

This last one you provided was kind of fun, but not on point.

... Now, we don't need to solve this mess to see that the choice of voltages, resistances, and phase angles can cause some of the source currents to be backwards so to speak. ...

Too late, some elf snuck in and solved it - twice. (Hopefully it wasn't a fairy:roll: ) (Please see as humor)

... That is the point that was raised a day or so ago.

Not by me. I still can't figure out why any one would want to set up a solution with the currents different sense that the sources. As Jim says, "Just because you can, doesn't mean you should."

carl

 

[mivey]

Well, I'm flat amazed that we both got it wrong:grin:

Okay, I'm not amazed you got it right, I'm amazed I got the equations correct (my coefficients look the same as yours - with the exception of a minus sign or two) and all the numbers punched in right.

I'm also somewhat supprised I picked all positive current flows by eyeball.

carl

Got to stop - my shoulder hurts from patting myself on the back:roll:

I had to go edit my edit because I ignored the CW CCW note. We are both correct all around. More patting all around:grin:

 

[mivey]

...Hopefully it wasn't a fairy...

It was the TRVTH fairy.:grin:

 

[coulter]

.... It was for fun anyway. ]

Absolutely - A couple of freeking geeks passing an hour solving a 9x9 matrix algebra problem. Some sould see this as sick.:grin:

Sick or not, I'm not doing one with complex numbers (that would be vectors to some, phasors to others):grin: till I get home and can use my other calculator.

carl

 

[mivey]

Absolutely - A couple of freeking geeks passing an hour solving a 9x9 matrix algebra problem. Some sould see this as sick.:grin:

Sick or not, I'm not doing one with complex numbers (that would be vectors to some, phasors to others):grin: till I get home and can use my other calculator.

carl

It really is odd what we do for entertainment. I'd rather do that than watch some junk on TV. I keep an HP at home and with me on the road. Took me about 10 minutes. 5 or so to write down the loops and double-check, about 2-3 to type into the calculator, check it, and punch solve. I spent more time making the pretty jpg than I did solving it!:grin: It would take longer to type in the complex numbers just because of the notation but the solver would still be a push of a button.

 

[rattus]

True, but not always:

True, but not always:

Yes, the currents came out right for the values you have chosen, but what if we let the resistors around the periphery be relatively small compared to the resistors in the interior. Also let V11 >> V99, then I9 would be negative for some values.

Of course, one would pick the currents as you have, however there are cases where the sense of the currents may not be obvious.

I am too old to bother with solving a 9x9, even on a calculator. I will brag a bit though and say I played a tiny part in the development of the hp line.

 

[coulter]

rattus -
I'm not seeing any evidence you're reading any of the posts (well, except your's). I'll respond if you get on point.

...I played a tiny part in the development of the hp line.

I thank you for that. You guys and girls did a great job. I really like my 17 year old HP-42. And the 11C before that. And the one before that - that I don't remember. I sure wanted that first one (35?) that came out (1971?) But I was out of the army and going to college and no way I could afford $400. You guys are right up there with my 6"circular Picket (That would be very high honors):smile:

...I am too old to bother with solving a 9x9, even on a calculator...

bummer - can't help you there.

carl

 

[jim dungar]

I am too old to bother with solving a 9x9, even on a calculator. I will brag a bit though and say I played a tiny part in the development of the hp line.

I did help write a program for solving 10x10 matrices, but it was done via punch cards and required special run permission due to the excessive processing time required. The program never went anywhere, within 6 months HP and TI calculators were no longer a fad and had become widespread.

 

[mivey]

...I will brag a bit though and say I played a tiny part in the development of the hp line...

Then I'll take back all the bad things I've said about you. I really like my 41CX, 48SX, 49G, 20S

 

[mivey]

I did help write a program for solving 10x10 matrices, but it was done via punch cards and required special run permission due to the excessive processing time required. The program never went anywhere, within 6 months HP and TI calculators were no longer a fad and had become widespread.

Punch cards? Now you've gone and dated yourself! I came in right after punch cards. I remember going with my dad to work on these machines (he worked with NCR). I used to have 1k? of memory which was about the size of a small laptop case and had 1000? little donut magnets in it. The best I remember there were three wires running through each one, one to set, one to clear and one to read.

 

[rattus]

??

??

Carl,

Then you believe you could never assign the wrong sense to an unknown current??

BTW, just what is the point of discussion at this moment??

 

[Rick Christopherson]

Carl,

Then you believe you could never assign the wrong sense to an unknown current??

BTW, just what is the point of discussion at this moment??

Not when solving a circuit, because the erroneous choice will be evident in the solution, and it will correct itself. However, remember that this discussion originated with a phasor diagram, which represents that solution.

Instead of correcting the "incorrect assumption" that you originated with, you carried the incorrect assumption into the final circuit solution and displayed it in the phasor diagram--the solution.

The odd thing about science--and this is science by the way--is that everyone can have their own methodology to finding the solution, but all of the solutions must be the same, regardless of the original path chosen.

 

[mivey]

The odd thing about science--and this is science by the way--is that everyone can have their own methodology to finding the solution, but all of the solutions must be the same, regardless of the original path chosen.

Don't I remember something about paths from thermo? It's been a while, but some of the processes are path dependent.

 

[mivey]

However, remember that this discussion originated with a phasor diagram, which represents that solution.

Instead of correcting the "incorrect assumption" that you originated with, you carried the incorrect assumption into the final circuit solution and displayed it in the phasor diagram--the solution.

I would like to go see what was said. Do you remember if it was from "Unbalance neutral current in a 3 phase system" or "Battle of the Phases" or "Phase versus Polarity" or "Four-wire delta, phasors, and Kirchoff" or "Hi-leg Delta xfmr reference?"?

 

[coulter]

...Then you believe you could never assign the wrong sense to an unknown current? ...

That's a pretty general statement. I'm certain one could find plenty of exceptions. For the screwing around we are doing now, I think the math will work out no matter the choice. For the stuff I do for a living, picking a non-intutive direction (okay - sense) is well, non-intuitive (now that was brilliant:roll: )

... BTW, just what is the point of discussion at this moment??

I think we are screwing around with some enjoyable conversation.

carl

 

[Rick Christopherson]

I would like to go see what was said. Do you remember if it was from "Unbalance neutral current in a 3 phase system" or "Battle of the Phases" or "Phase versus Polarity" or "Four-wire delta, phasors, and Kirchoff" or "Hi-leg Delta xfmr reference?"?

It started with Four-wire delta, phasors, and Kirchoff

 

[coulter]

... it was done via punch cards ... quote]
1971-73, UW, CDC6400, 80 column punch cards - Fortran 4?, ran the bigger stuff through a compiler first, then put the machine code stack in the bin and waited for you output. yeah I remember doing that.

... it was done via punch cards ... within 6 months HP and TI calculators were no longer a fad and had become widespread.

Bought a TI in 1975, 100 for the calculator, 100 for a print cradle, programmable with a 1 x 5 mag strip - still couldn't afford an HP. Took my EIT exam with it in 1975 - worked great

carl