Which is the correct diagram to obtain only a 240 V secondary output from a 480 V primary for a transformer rated at 480-240/120 V?

Question

I know the answer I just wanted to know what A, and C were if I put my meter across. Could someone also show me where I'd put my meter leads? Or if those are dud/fake transformers.

score 1 · Accepted Answer · answered Aug 19 '23 at 16:53

A 480—240/120 volts transformer has one 480V winding (upper winding in your schematics) and two 120V windings (lower windings in your schematics). You have to wire both 120V in series to get a 240V output.

A has an open circuit, so you get two independent 120V circuits.
B has them in parallel, so you get one 120V circuit with doubled current capacity.
C has them antiparallel, so this is a dead short at 0V.
D has them both in series, so you get the desired 240V circuit.

Which is the correct diagram to obtain only a 240 V secondary output from a 480 V primary for a transformer rated at 480-240/120 V?

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