[lgalla]

Does aVFD keep the torque of the motor at low speeds?
I assume a variable speed router does not.Can a VFD be used on a Porter Cable
type router?
Thanks
Larry

[Al_The_Man]

Some VFD's are capable of high torque down to low RPM as used in Elevator and Hoist applications, where a load can be held stationary, also use of an encoder option helps to control precise rpm.
A VFD outputs 3 phase, Porter Cable are generally Universal Motor, so cannot be used on a VFD.
Al.

[JRaef]

In general, VFDs cannot be used on 1 phase motors. There are a few available that work on a selected few types, but not the type you would find in a hand power tool. As Al_The_Man said, it is likely a universal high speed motor. If you were to get in to the guts and get bold with clipping wires, you could theoretically insert a variable resistor (Rheostat) into the power circuit and slow it down, like a variable speed drill does, but I wouldn't. You may end up changing the cooling capabilities of the motor and toast it really fast. If it wasn't designed as variable speed, don't mess with it.

[Al_The_Man]

If you were to get in to the guts and get bold with clipping wires, you could theoretically insert a variable resistor (Rheostat) into the power circuit and slow it down, like a variable speed drill does,.

This is usually done now with a triac, there is a low wattage pot. in the trigger, but this is for the firing circuit.
For a router you can fit a triac controller externally.
Al.