I asked my husband, who is an expert on motors, transformers, and electrical stuff in general.
His reply was that if the power was on for a minute or more (ballpark, of course), chances are good that the motor windings are toast -- the insulation on the wire gets too hot and starts to disintegrate. It shouldn't be too hard to open the unit up enough to look at the windings -- if you see blackened areas and crumbling insulation that would tell you something. I've found that your nose can also help guide you to areas of damage after an event like this (burnt electrical components stink).
Shorter exposure to 240 might have first hit support components, such as a starting capacitor, if there is one in this device. DH said that fan motors often don't have a starting cap, but that a blower that bubbles air through water might. His opinion was that it is "very easy" to take out the cap and test its health with a meter. Perhaps not quite so trivially easy if you've never done this procedure before, I would guess.
In any case, probably worth your while to look inside, if you haven't done so yet.