I am trying to select a motor for a high-speed application where I need to rotate a load bearing cylindrical disc at 20,000 rpm. The total mass of the disc along with its load is approximately 1.5 - 2 kg. I'm attaching a diagram of my application along with this question. Kindly help me define the motor torque parameters for this application.
I guesstimating that you will need around .4Nm of torque for this (around .3 ft-lbs) and at 20,000RPM is going to be almost 1kW. That's somewhat high for a direct drive motor moving a 2kg load in my opinion. A "universal" motor (those found in things like blenders and routers) can get to those speeds, but are not likely available in big enough sizes to spin something that big. You will probably be looking at something very expensive like a 2 pole AC "spindle motor" driven by a VFD operating at 333Hz. So yu are looking at roughly speaking, $1000 US. Is that in your budget? the point being, you might want to consider using some means of mechanical speed increase so as to use a more standard low cost motor that will run at around 3000RPM.