>I have an Harrison Model AA-10 lathe with a 2HP motor with a dodgy
>I need to replace the variator.
>I am uneducated in these devices, but it has been suggested that a VFD
>setup would do the trick. (I need to be able to reverse, if that is a
>factor that need extra consideration.)
>I have three phase power available at the lathe and a budget of about
>$1000 with some wiggle room.
I assume this "variator" is some form of variable speed drive.
Depending on what the output speed of the variator is, you may be able to
use a standard 3-phase motor directly, or you may need a separate reduction
gearbox between the motor and the rest of the lathe.
But, the variable speed part is straightforward. Without forced-air
you can get about 30 - 150% speed from a standard motor. With heavy
external cooling applied, you can get from 5% up to wherever your danger
threshold is. I don't feel too comfortable spinning large motors much more
than 50% above rated speed.
With a VFD, you get rated torque from 0 - 100% of the motor's rated speed.
Above 100% speed, you get constant HP, so up there is works just like a
variable speed drive. But, below rated speed, the power drops off linearly,
UNLIKE the VSD. If the variator accomplishes a great deal of speed
then just bypassing it may lead to a loss of low speed torque. If you
low speed ranges from other gear reductions, like in the headstock, then it
shouldn't be a problem.
All VFDs can handle reverse. Pretty much all of them can also brake the
motor, which is a nice feature.
I have a Sheldon R15-6, which was made with 8 fixed speeds. (4 speed
gearbox on the motor, and backgear in the headstock.) It is wonderful with
a VFD. I get smooth starts, braking, plus a jog function for certain
gears that don't
want to click right in.
If you have a dual voltage (230/460 V) motor, and you set it up for the
voltage and run it with a 230 V VFD, you get an extra level of insulation
protection. VFDs can be *** motors, but by using a motor with 460 V
insulation with a 230 V VFD, you should have no problems with insulation