HY VFD and spindle at low speed

[Jonathan]

Fossilised somewhere on this forum (4-5 yrs ago) there's a thread/post where I've discussed how to get more torque from the common 2.2kW spindle and HY VFD combination at low speed. Essentially you use the voltage vs frequency mapping settings to boost the voltage applied to the spindle at low speed. This will put more current through the stator windings, so in my case I had something like 2-3 amps read by the VFD at just 4800rpm, but it did give me enough extra torque to drill aluminium with a 4.2mm HSS drill at that speed.

Adding extra heat in the stator is not too big a deal - in theory you could go all the way to the current rating of the winding, and a bit more as the iron losses should stay fairly small at low speed. However this will induce extra current in the rotor, which is much harder to get the heat out as it's not directly water cooled. I did once characterise the 2.2kW spindle to find the equivalent circuit, so you can work out how much current is permissible in the stator to have the same rotor losses as it was designed for. How much torque you actually get out of this is harder to say though, as we don't know the saturation characteristic of the stator. Not sure where that spreadsheet is now though.... so I suggest you increase the voltage until you see a few amps with no load and see if it's enough.

Another approach is to use a cutter with the right coating to enable raising the spindle speed. These have worked well for me:
https://www.shop-apt.co.uk/carbide-e...ted-65hrc.html