Hi there.
I may be right or wrong here, this just for consideration only. Regarding the fuse. In the traditional sense, yes, you would not get continous 1500W through 3A fuse. This fuse does not cut power entirely to the unit. It seems the fuse only protects the driver (amplifier) and digital sections in the PP, which run at a lower voltage and draw less current.
The push button is resettable thermal switch rated at 10A, below is its response curve. It looks to be connected in series with the fuse.
Regards