Again I don't understand. If you don't use half of the windings, then you'd still get the same power output as when you used them all?
Yes - that
is how a transformer works: a transformer is an
incredibly simple, but not intuitive device: ultimately, you can draw current up the total VA design limit
indefinitely from any secondary winding or distributed across them - the limit is the flux linkage between pri:sec. ;
plus the losses you incur in the winding and core
(which are - in comparison, for obvs reasons - designed to be rather small) - AND, providing
only that the secondary winding(s) used, can safely deliver the total current demanded to deliver that power [i.e. without overheating long term]
so 'unused' / under-used' windings represent no issue, since they are no load whatsoever: it is only the total load on the output side that matters.
Ex. 1: If I have some weird trafo - oh, lets say, 1x24Vac, 1x 12Vac , 1x 6.3Vac, and I only draw from one or two windings - the
total capacity of the transformer is available, on those windings: providing
only that they are up to the current that represents.
Ex.2: say we have a notionally 100% efficient, 100VA transformer, with, oh 100Vac, 10Vac and 1Vac windings:
- if I only use the 100Vac winding I can load that to the full 100Va - notionally, 1A rms. wiring dissipation proportional to 1A = I^2 = 1unit x R(winding)
- if I only use the 10Vac winding I can load that to the full 100Va - notionally, 10A rms. But better hope the secondary wire gauge windings are up to that ..likely not. wiring dissipation proportional to 10A = I^2 = 100unit x R(winding)
- if I only used the 1 Vac winding I can, perhaps, load that to the full 100Va - notionally, 100A rms! Except obvs unless that winding is nice wide fat & flat copper-strip that wont last any time. wiring dissipation proportional to 100A = I^2 = 10000unit x R(winding)
So we can load the secondaries up to the VA limit in any combo we choose, up to each secondary winding's heat disspataion limit - with no penalty: If I only use it to draw 10Vac at 0.1A for some modest purpose - well, the transformer only draws c 1w (+ inherent core losses) from the wall; the rest of the VA capacity is
not used;
nor inhibited.