Davey, I'm not formally electrically qualified, my electrical engineering skills/qualifications are related to telephone exchanges, but one thing jumps out at me.
It may well be that I'm missing something on the photo(s) of your inverter.

It looks like it's mains fed from two core cable, with no earthing back to the supply side. I'd be inclined to use 3 core, of appropriate size and fusing.

Similarly when you get to the motor end, I'd add another length of Green/Yellow from the motor frame termination back to the main drilling machine itself.

The motor side connections in the inverter look OK at U-V-W + Earth
Personally I prefer to leave the earth tail longer than the phase wires; that way should the cable get heavily snagged, the earth is the last one to become disconnected.

Have a look in my album on here for a way of making a compact ring terminal for the motor end of the 3 phase cable; they are just leatherworkers eyelets.

The inverter end is designed to accept either bare wires or a pin termination; just make sure there's no straggly bits if you use bare wires.

Bill

p.s. NDIY beat me to it with less typing. 

Edited By peak4 on 29/09/2019 14:50:09