I have finally fired up a 2.4kw 24,000 rpm spindle on the test bench. This has water cooling and is VFD controlled. The spindle runs on 3 phase AC power.
One thing that is not mentioned much is that the spindle itself and bracket runs to around 6-7kg. Below is the spindle hitting 24,000 rpm for the first time.
With this and some other bits a 3040 should be able to machine alloy.