VFD/Potentiometer/Motor Questions

I'm hooking up a VFD to my 1961 vintage 9" South Bend lathe (with .5 hp, 208 vac, 3 phase motor) and I have a few questions.

I can hook up an external pot to control the speed of the lathe. The specs says the pot has to be between 3K - 5K ohms. What would be the difference in operation if I were to use a 3K ohm pot vs a 5K (or vice versa)?

What would be a reasonable maximum speed for the motor? The nomenclature plate says 1725 operating rpm, but I understand with a VFD you can go much higher. I don't want to hurt the motor, but the extra speed would be nice when using carbide. I've also got the ramp up and deceleration speed currently set at two seconds; is this reasonable?

I knew nothing about VFD's when I started the installation (I'm still not quite finished), but I have to say that it sure seems slick. Not sure of the advantages/disadvantages of using a VFD compared to a static phase converter (which is what I was using before). I understand with a static phase converter you lose 1/3 of your horsepower, not sure if the same thing happens with a VFD. I'm hoping not...

Thank you!

Dave Young
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Relevant Pages

  • Re: VFD/Potentiometer/Motor Questions
    ... I had taken off the motor and checked the wiring. ... Dave Young wrote: ... The nomenclature plate says 1725 operating rpm, but I understand with a VFD you can go much higher. ... Not sure of the advantages/disadvantages of using a VFD compared to a static phase converter. ...
    (rec.crafts.metalworking)
  • Re: VFD/Potentiometer/Motor Questions
    ... I had already ordered twenty feet of 18/4 shielded wire from Ebay for both the pot and for the drum switch (the VFD does in fact have 10 volt control voltage). ... The motor was made by Westinghouse. ... in several speeds of motors by the same manufacturer, ...
    (rec.crafts.metalworking)
  • Re: VFD/Potentiometer/Motor Questions
    ... On Fri, 11 May 2007 01:50:01 GMT, Dave Young ... I can hook up an external pot to control the speed of the lathe. ... What would be a reasonable maximum speed for the motor? ... nomenclature plate says 1725 operating rpm, but I understand with a VFD ...
    (rec.crafts.metalworking)
  • Re: 3 phase speed control
    ... Most vfds support a number of different options as to controls -- a pot for speed, a number of different switch configurations for start/stop/direction. ... Also, the vfd parameters control the min and max rpm, how much power will be imparted to the motor, etc. ... Low speed running causes the motor to heat up and the vfd rated motors have high temperature windings and better cooling systems. ...
    (rec.crafts.woodturning)
  • Re: 3 phase speed control
    ... I like the idea of moving the VFD to the lathe and finding help ... cost you more than the pot. ... Also, the vfd parameters control the min and max rpm, how much power ... will be imparted to the motor, ...
    (rec.crafts.woodturning)
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