VFD for drill press

[Noplace]

There's a lot of good info here but possibly not so useful to someone without the technical background to follow the discussion!

In short, I think that the answer to the original question is, yes, fixed pulleys with variable-speed motor is a practical proposition, but you need a VFD plus replacement 3-phase motor to do it. You can't make a simple single-phase motor into a variable speed motor just by feeding it from a VFD - unfortunately.

lots of great information surfaced in the thread, appreciate if you can just let me know what would be the problem in using a 1ph VFD?
got my eye on this one http://www.ebay.com/itm/0-75kw-Frequ...16402#shpCntId and seems it would work, am I missing something?

[magicniner]

lots of great information surfaced in the thread, appreciate if you can just let me know what would be the problem in using a 1ph VFD?

It's 1 phase input but it's 3 phase output for use on a 3 phase motor, not a single phase motor.
You can buy a good new 1hp 3 phase motor for around £120, once you've tried a drill press with an inverter you'll never go back, jus do it ;-)

[Boyan Silyavski]

Somebody know where they sell cheapest the 500w variable speed DC motor for the small chinese mills?

[Neale]

lots of great information surfaced in the thread, appreciate if you can just let me know what would be the problem in using a 1ph VFD?
got my eye on this one http://www.ebay.com/itm/0-75kw-Frequ...16402#shpCntId and seems it would work, am I missing something?

As Magicniner has said, these VFDs take single-phase in and produce a 3-phase output that is designed to drive a 3-phase motor. Why can't you just use two of the output connections and drive a single-phase motor? Main problem (there are others) is that the motor will probably not start unaided. Single-phase motors have some clever bits in them to get them started from stationary; you often hear a click from inside the motor as they spin up to speed. This is the centrifugal switch cutting out the starter circuitry (often a capacitor bolted to the outside of the motor). This is all designed to run at a single speed. Imagine a children's swing in a playground. It swings at a steady speed, and you just need to give it a nudge at regular intervals to keep it swinging. That's the way a single-phase motor works, where the incoming alternating voltage generates a magnetic "pulse" that is synchronised with motor revs. 3-phase motors work differently - the three phases generate what looks to the motor like a rotating magnetic field at the frequency of the input voltage, and the motor follows this whatever (within reason) the speed. Obviously, it's all a bit more complicated than that, but I hope that this helps.