I have a 1998 Toyota Rav4 4WD 2.0 liter with 195K miles and the 20amp fuse (rated) keeps blowing. I even went so far as to install all new fuses for all the other components so that none would be old fuses, yet, the only fuse that blows is the winshield wiper.
The only good thing going for me is living in the desert southwest where it rarely rains, but this still poses a big problem for me.
Looks like your motor its pulling to much current and or you have a bad wiring.
Check if the wiper motor gets " hot" if you have an amp meter check the amps its draining if too high replace the motor.
If normal. (10-15 amps) check the wires that feeds the motor could be a short circuit somewhere.