3PH motor wiring

[MikeInOr]

Make sure your VFD is rated at 3Hp and the output amps are sufficient for that size motor, that is a big increase in Hp for that size lathe. You may also use a smaller motor pulley and over speed the motor to something like 100Hz, will give you a wider speed range.

The motor on my South Bend 13 runs smoothest at 80-100hz. The whole lathe is quieter and smoother. I always figured 60hz is an artificial limit for motors because it is what the power company gives us. Even though the motors are designed to run at 60hz I don't believe that means it is the frequency they might run best at.

 

[RaisedByWolves]

Yea, I don’t really get reckless with it. I tend to over build everything I do so this is no different. The machine I have is pretty ridvged for a 12” lathe and the added weight of the bigger motor should make it a little heftier. I do understand what you are saying but I’m gonna go with it. So I have more power and torque than the machine actually needs. Doesn’t mean I got to spin the jaws out of the chuck. I have a mini lathe/ mill combo that came with 2 hp motors from the factory. Absolutely unnecessary but that what they did,lol

Comparing the size/capacity of the lathe regarding the HP of the motor or what the lathe will actually vary greatly depending on the design of the machine.

A coarse leadscrew that turns slowly will require more power due to frictional losses than a finer pitched lead screw turning faster.

A lathe that uses belts for speed change will use more power than a gear head lathe as there are more frictional losses in the change belts (figure 3 belts) than there are in the single or double drive belt of the gear head.

Those same three belts also induce friction in the bearings of the shafts they run on and also pickup friction from the banjos not aligning the middle sheaves perfectly.

And so it goes, yet we haven’t even touched the tool to the work yet.

 

[Pevehouse]

Comparing the size/capacity of the lathe regarding the HP of the motor or what the lathe will actually vary greatly depending on the design of the machine.

A coarse leadscrew that turns slowly will require more power due to frictional losses than a finer pitched lead screw turning faster.

A lathe that uses belts for speed change will use more power than a gear head lathe as there are more frictional losses in the change belts (figure 3 belts) than there are in the single or double drive belt of the gear head.

Those same three belts also induce friction in the bearings of the shafts they run on and also pickup friction from the banjos not aligning the middle sheaves perfectly.

And so it goes, yet we haven’t even touched the tool to the work yet.

That’s a lot of power loss right off the bat. It’s a lot like hp loss in a car. That’s why there are specs for crank hp vs wheel hp. That being said, my 3hp motor will probably yield only 2 at the chuck