Toroidal power transformer question

[TimFox]

Medical-rated toroidal isolation transformers are readily available with two 120 V primary windings and two 120 V secondary windings.
Some have 100 V taps on the primary windings.
Since these transformers are rated for 50/60 Hz, I assume that it would be safe to apply 120 V, 60 Hz to the "100 V" taps, increasing the nominal output voltage from 120 V to 144 V.  120 V at 60 Hz requires the same core flux as 100 V at 50 Hz, so the core should still be below saturation.
In this case, I also assume that the VA rating remains constant, and that therefore the secondary current ratings scale down by the same factor.
Is this correct?

[Zero999]

Yes, if the transformer is rated to 100V at 50Hz, it should be safe to operate it at 120V on 60Hz. The VA rating will not remain constant, but increase because the copper losses are proportional to the current.

The hysteresis losses and insulation still limit the ultimate maximum voltage and frequency ratings, so don't try 1kV at 500Hz, but 120V will do no harm and it's already rated for 60Hz operation.

[Dave]

No. The current capability of the transformer is limited by the cross section of the winding, as the losses inside a loaded transformer are predominantly resistive. You should be able to put more power through it than nominal.

Edit: It seems that Zero was quicker.

[TimFox]

Thanks for the replies.  There seem to be no standard products with 140 V secondaries, so this seems to be my best option.