You might struggle to get enough torque by only using one gear/ratio for the entire speed range.
Going by the online calculator I just used, 1.5Kw at 3000RPM gives 4.77Nm, which will remain constant over the speed range. Certain motor/VFD combos can boost that for short period of times.

You might want to run some figures through something like FSWizard or G-Wizard, to see what the estimated torque is for the work you're planning on doing.

If you're planning on running the motor at low speeds for extended periods of time, you might want to consider a motor with a separately powered cooling fan, otherwise there is a good chance it'll overheat.