/ HELP - last considerations before building 1750x1000x250 mm all-around milll

[Jonathan]

1. Does using sensor less vector mode give better toque at lower revs, on a standard setup.

Yes.

2. Is this enough of a difference to be usfull ?

That's a much better question! It depends what you're trying to cut. If you're trying to drill aluminium with HSS drill bits, or mill steel with standard (i.e. no special coatings) carbide cutters (i.e. anything that needs higher torque at low speed0, then the difference will be tangible, but that doesn't mean you can't get away with a cheap V/f control drive. If you're just milling aluminium and cutting wood/plastic etc, then you wont really gain anything.

Yes, the VFD will be used in sensorless vector mode which is not as good as the closed loop type

Sensorless vector control is still closed loop - you're just inferring the rotor position electronically (i.e. from the back-emf) instead of from using an encoder. That indicates the situation where sensorless control isn't as good - it relies on the back-emf which is hard to sense at low speeds, so it's necessary to have field oriented control with an encoder if you need full torque down to zero speed.

If the limiting factor is the difference in torque between the control algorithms, you should probably look into getting a bigger (e.g. 3kW) spindle and stick with the cheap VFD.