Re: A question about motors


fwhite913
 

VFD and Variable Speed DC motors are constant torque designs.  Pulley, gear speed reductions, etc are constant horsepower.  Simply using a VFD or DC controller probably won't work....you still need step pulleys, etc.  On a treadmill motor, check the motor HP and the speed at which that HP is rated- you may find the treadmill motor has much lower torque at speeds you want to run the lathe at.  

 

Best plan is a slightly oversized motor rated at 1750-1800rpm with a VFD or DC drive ( depending on the motor ).Then continue to use the lathe step pulleys for coarse speed adjustment and the VS drive for fine speed adjustment. 

 

I once heard of a person trying to use a 7.5HP 3 phase motor with a VFD on a Clausing lathe ( originally 1 1/2 or 2 HP ) so he could eliminate step pulleys.  Neaver heard how that turned out......

 

There has been much discussion on this subject over the past years on "www.practicalmachinist.com

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