Hi greybeard, be carefull using a VFD on a small (1/4hp) induction motor. As you appear to be into model engineering and are using a table top type lathe, then the "want" from your end is a speed range from about 50 rpm for cast iron etc and 2000 rpm for small drilling and polishing.
The problem is, induction motors run slow get HOT, and as you will be simulating a lathe in back-gear then the torque low down will only be achieved by pumping the amps into the coils in a virtual dead stall situation.
The electric drill method will work but the whining of the motor will drive you nuts. If this is an option then try a vacuum cleaner motor, or angle grinder, modified, with a light dimmer switch rated at about 350 - 500 watts.
Top speed of the vacuum motor is about 10,000 rpm so if you belt this down by vee pullies to 2000 rpm input then the motor will still get some cooling running slow.
The best option for your case is to use the induction motor "as is", and arrange a variable VEE pulley drive to get speed change.
They're not hard to make, and if you use standard vee belts, just use two variable pulleys in compound arrangement. This way you still get "dial up" speed control on the move and plenty of low down torque.
Ian.  |