Transformer Test question

[Johnnyb82]

A transformer with a nameplate rating of 240/480V pri - 120/240V sec can be connected to a 2-pole breaker in a ___ panelboard and deliver nameplate-rated voltage to a load.

I. 120/208V 3ph 4wire
II. 120/240V 3ph 4wire
III. 277/480V 3ph 4wire

a. I, II, III
b. II, III
c. I, II
d. III
e. II
f. none

I've asked 3 coworkers and have gotten 3 different answers so far. Can someone help me out?

 

[iceworm]

...
I. 120/208V 3ph 4wire
II. 120/240V 3ph 4wire
III. 277/480V 3ph 4wire

This is homework, so what is your thinking and why?

Here is some guidance. First you need to look up connection diagrams for this transformer.

From the information you have, the transformer primary is 1 phase, with 2 each - 240V windings.
primary 240/480: This tells you there are two primary coils each rated at ___V.
Connected in series, the primary voltage is ___V
Connected parallel, the primary voltage is ___ V

You fill in the blanks. Then pick the panels that can provide the required voltages.

If you get stalled, come back and tell us and I'll add some sketches.

the worm

 

[LarryFine]

Ooh! Ooh! I know! Pick me!


Actually, I do know, but agree the OP should answer first.