May I ask a question about the single vs two phase stuff

Status
Not open for further replies.
I

Ingenieur

Senior Member
Location
Earth
'in phase'
1/0 = 1 + 0j
1/0 = 1 + 0j

Vll = 1 + 0j + (-) (1 + 0j) = 0 + 0j = 0/ (arctan 0) = 0/0
the (-) must be in there since the loop is followed in 1 direction and opposed to at least one line
in other words NO voltage if 'in phase', ie, of the same phase

where is the math 'incorrect'?
 
J

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Ingenieur said:
'in phase'
1/0 = 1 + 0j
1/0 = 1 + 0j

Vll = 1 + 0j + (-) (1 + 0j) = 0 + 0j = 0/ (arctan 0) = 0/0
the (-) must be in there since the loop is followed in 1 direction and opposed to at least one line
in other words NO voltage if 'in phase', ie, of the same phase

where is the math 'incorrect'?
Click to expand...

Finally we get you to agree that switching polarity is just as good as shifting 180 degrees. Glad we're on the same page there.
 
Besoeker

Besoeker

Senior Member
Location
UK
jaggedben said:
Finally we get you to agree that switching polarity is just as good as shifting 180 degrees. Glad we're on the same page there.
Click to expand...
No "shifting" takes place. You don't take one phase and shift it to get to the other. Polarity is a bit meaningless on alternating quantities. Both phase positive and negative over a cycle..
 
J

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Besoeker said:
No "shifting" takes place. You don't take one phase and shift it to get to the other.
Click to expand...

Semantics, in my opinion. If you like, using a -1 multiplier is just as good as adding 180 degrees to the input of a trigonometric function.

Polarity is a bit meaningless on alternating quantities. Both phase positive and negative over a cycle..
Click to expand...

Sigh. It's not meaningless. Hook up the wrong dot end of the transformer core and you have a practical problem. This has been discussed.
 
Besoeker

Besoeker

Senior Member
Location
UK
jaggedben said:
Semantics, in my opinion. If you like, using a -1 multiplier is just as good as adding 180 degrees to the input of a trigonometric function.
Click to expand...
No mathematics required. Hook up a two channel scope and you can visually observe the two difference phases.

jaggedben said:
Sigh. It's not meaningless. Hook up the wrong dot end of the transformer core and you have a practical problem. This has been discussed.
Click to expand...
The dot notation indicates the start and finish of the winding, not its polarity.
 
jumper

jumper

Senior Member
Location
3 Hr 2 Min from Winged Horses
winnie said:
If the math works to correctly predict the physical world, then the math is correct.

The math matches the electrical theory.

The fact is that you can do the math multiple different ways and get the same result.

All of these approaches are correct.

L1-N and L2-N are part of the same single phase system. They can quite reasonably and correctly be represented by two vectors, one 120V at 0 degrees and 120V at 180 degrees. That you _choose_ to use a different representation does not make this incorrect.

-Jon
Click to expand...

:happyyes:
 
jumper

jumper

Senior Member
Location
3 Hr 2 Min from Winged Horses
jaggedben said:
Glad two people on this thread see eye to eye. :thumbsup:
Click to expand...

We having fun yet?:D

Yeah, the semantics and refusal to see or understand a different point of view does these threads in all the time.

Just because I prefer one methodology over another in certain cases certainly does not mean that I ignore or refute another.

Heck, if people would just read that damn tutorial, they would see that!
 
W

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Besoeker said:
Polarity is a bit meaningless on alternating quantities. Both phase positive and negative over a cycle..
Click to expand...

Going to disagree on this point. Polarity has a very important meaning; it describes the sense of the measurement. While the AC cycle is both + and - over the cycle, you also need to specify the sense that the meter is connected.

We should probably say 'red and black' for the meter leads, rather than + and - :)

If polarity had no meaning than a 180 degree phase inversion would not change anything, the opposite of what you've been arguing!

-Jon
 
J

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Ingenieur said:
never said it wasn't
only that the phase angle IS the cause of the reversal
Click to expand...

Your invocation of causality is baffling. A reversal is the same as a rotation of 180deg, by any common definition. One does not cause the other, they are two phrases that describe the same thing. Like 1-1=2-2. One side of that equation does not cause the other.
 
Status
Not open for further replies.
Top