I am retired Navy electrician - not a motorcycle mechanic... so for what it is worth - there are a few items that would draw that kind of current.
I would start by checkng the battery leads and the ground screw on the frame forward of the battery. If they are tight, suggest pulling the battery and inspect the leads around the frame from the positive side (red) and the frame. Inspect the leads to the starter and voltage regulator. There is tight clearance around the battery and you may have worn the insulation away. Electrical tape if you see any metal should get you home. Sounds a bit intermittent as you were able to drive one time for 15 minutes.
Generator - short circuit in the stator. The rotor has permanent magnets, so that is not a likely source. If there is a ground path from "wear" dust, oil, dirt etc you could be getting a short to ground drawing that type of current. In either case, it is not a fast repair as you need to pull the right engine cover.
Voltage regulator - this is a go or no-go situation either they work or fail. Not sure if you can just unplug it and run off the battery to see if the fuse blows again. If it runs on the battery, and does not blow the fuse, you have found the problem. Obviously, not a long term solution as the battery will dischage.
Part numbers from Kawasakipartshouse.com
21003 21003-0076 STATOR $330.08
21007 21007-0116 ROTOR $599.03
21066 21066-0043 REGULATOR-VOLTAGE $139.65
Starter - with the new fuse, does the starter disengage? if the solenoid does not release, that could draw enough current to blow the fuse. If you are able to get it running, I might suggest holding the lead on the starter to get it running and then pulling it away once running. If it is hard starting, the brushes may be worn out and causing the short, but solenoid should release.
1039 21039-0009 BRUSH $22.93
21040 21040-0003 SPRING-BRUSH $5.28
21163 21163-0055 STARTER-ELECTRIC $493.88
27010 27010-1446 SWITCH,MAGNETIC $77.67
Good luck - and hope it is a simple fix.
EMCM(SS) USN Ret.
09 Vulcan Nomad Diablo Black
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Kuryakyn Power Port
RAM GPS mount
Voyager Trunk Kit ($OUCH$)
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Removable windshield Kit and Lowers!
K&N Air Filter
Day-Long Seat (best seat ever!)
Red Line 10w-40 MC Oil