Transformer Question

[mivey]

I disagree. Not only are they possible but I think that they are exactly what you would get.

I don't agree.
To help illustrate, assign primary L1-N the value +120 and L2-N the value -120. We can just use N as the reference and say L1=+120 and L2=-120.

Similarly for the secondary side, let N be the reference and we have L1=-60, L2=+60, L3=-60.

The left terminal of the left transformer is at 60 volts below the middle terminal, the right terminal is at 60 volts above the middle terminal.

The left terminal of the right transformer is at 60 volts above the middle terminal, the right terminal is at 60 volts below the middle terminal.

Going from N to L1 we drop 60 volts so L1=-60

Going from N to L2 we rise 60 volts so L2=+60

Going from N to L3 we have a 60 volt rise, a 60 volt drop and a 60 volt drop so L3=-60

L1-L2 = -60 - +60 = -120
L1-L3 = -60 - -60 = 0
L2-L3 = +60 - -60 = +120

To get 240 volts somewhere, you would have to change the connections between the two transformers as they are connected in opposition. If you connected them right-terminal to right-terminal you could get 240 volts

 

[mivey]

Swapping the primary on the second transformer I get:
L1-N = 60v
L2-N = 60v
L3-N = 180v
L1-L2 = 120v
L1-L3 = 0v
L2-L3 = 120v

That should have read
L1-N = 60v
L2-N = 60v
L3-N = 180v
L1-L2 = 120v
L1-L3 = 240v
L2-L3 = 120v

Which agrees with Larry

 

[Eric R 1973]

How will you bring L1 L2 L3 of the sec to 120 degrees out of phase?

 

[mattsilkwood]

That should have read
L1-N = 60v
L2-N = 60v
L3-N = 180v
L1-L2 = 120v
L1-L3 = 240v
L2-L3 = 120v

Which agrees with Larry

Explain to me what swapping the primary will do. There must be something I'm missing.

 

[mivey]

Explain to me what swapping the primary will do. There must be something I'm missing.

It changes voltages rises to voltage drops and vice-versa.

Assign phase angles to the voltages and you will see what I mean.

 

[mivey]

It changes voltages rises to voltage drops and vice-versa.

Assign phase angles to the voltages and you will see what I mean.

Like so:

As is:

Primary swapped:

 

[LarryFine]

Which agrees with Larry

That's because Larry redrew the diagram before posting his answers.

 

[mivey]

That's because Larry redrew the diagram before posting his answers.

He's smarter than the average bear. :grin: