Try this analogy for the vector challenged folks, an analogy that has been helpful to others.
You have a spring scale at the 6:00 o'clock position attached to a plow tied to a stump with 2 ropes attached.
You and a buddy stand side by side at the 12:00 o'clock position and pull with 120 pounds on the ropes, the scale reads 240 pounds.
Now, you go to and your buddy to 10AM and 2PM positions and both pull again with 120 pounds force. Due to the vectors, the scale reads only 208 pounds. Where is the other 32 pounds combined - you and your buddy are pulling on each other sideways.
No work done yet, just force applied.
Now you untie the plow from the stump and both pull on the rope from the 12 o'clock position, and 240 pounds pulls the plow thru the ground at a certain speed (aka current) producing work. If you go to the 10 and 2 o'clock positions, you cannot pull the plow as fast but you do end up walking in parallel lines because you are pulling against each other (but doing no work on each other as you are not moving relative to each other), The plow is not going as fast and you are pulling less force going into pulling the plow, (aka lower current * volts, less work), so the total work being done is less.
To realize the vectors in how you think you are still pulling 120 pounds but really are not, attach a pole from the 10 to 2 o'clock positions. This pole now can provide the force between you and your buddy (e.g. 32 pounds), so now, parallel to each other you are only pulling 104 pounds in line with the direction the plow is going rather than 120 pounds in line with the ropes. You let the pole take the sideways static 32 lb. force, and you are each contributing 104 pounds to pulling the plow.
re: in other word because of circulating currents in the Delta system it is just as inefficient as the Wye system.
Hoo boy, do we want to get into a discussion of triplett harmonics and delta - Y transformers -- other than that, the italic statement is false.
If one had a transformer with superconducting wire and no hysterysis or eddy current core losses, both delta and Y transformers would be 100% efficient.
The phrase "just as inefficient as the Wye system" indicates there are still basic misunderstandings of how transformers work. Very hard to do on-line as some basics such a phase vectors, etc. are missing in OP's knowledge base - hopefully the rope analogy above can help with that?