Yet another transformer question...

Temp rise, is this the max. operating temp of the transformer.

Reason for question, I measured a trans, 480x208/120y, that was operating at 25-30% load, and the internal temp was 296-300F degrees. It stated on the nameplate a temp rise of 150C, which closely puts it at 330F.

Is that the max operating temp? The insulation class is listed at 220C.

Thanks...

Dnk.....