3ph vs 1ph, or transformer + converter for lathe

[farm boy00]

I would do the single phase 240 also and keep the old motor. Really good resale value later on for someone like you or me that only have single phase

 

[LD1]

I would keep it simple and just get a single phase 240 motor. A 5hp motor drawing peak is only going to draw 15.5amps, so you can plug it into any 240vac 20amp receptacle. Makes for relocating in the shop pretty easy. I知 assuming this is just hobby stuff, given that youæ±*e humming and hawing over a few hundred dollars.

More like 23a....

But yeah, I have plenty of 240 juice at the shop. Two 50a plugs and two 30a plugs. No worries either way.

Just wondering if there was any reason I am overlooking to keep 3 phase ....either low voltage or high.

 

[Mendonsy]

The only "reason" I can think of is that a 3 phase/VFD setup would allow you to adjust the motor RPM over a fairly wide range. On a lathe there probably isn't any real need to do that but it can be real advantage on things like milling machines and drill presses.

 

[Kyle_in_Tex]

What other controls does the lathe have? Coolant motor 3 phase high voltage too?

single phase motor option might require a bit more to go that way too.

 

[LD1]

What other controls does the lathe have? Coolant motor 3 phase high voltage too?

single phase motor option might require a bit more to go that way too.

No coolant pump. No other controls.

1960's lathe dont have much electric stuff

 

[Cord]

...or replace the motor with a 220v 3ph unit and use a vfd to control it. If you are replacing the motor, it might be easiest to just replace it with a polyphase unit and then not bother with the vfd.

 

[Mace Canute]

A friend bought a big (18" capacity) old Sebastian lathe a little while back and it originally had a three phase 480/240V motor, 3(?) HP I believe. He opted for a single phase 240V 5 HP motor since the shop only has a 240/120V service.

Even though we could have built a rotary converter (I have a spare 7 1/2 3 phase motor) we decided it was easier and simpler to swap motors since he had found a very reasonable priced used 5 hp single phase motor. With a new starter switch and repacking the bearings (which were still in great shape) and a paint job, it's like brand new again

A VFD will work as will a step up transformer but the simplest solution is to swap motors. The KISS principle, eh?

 

[buickanddeere]

The VFD gives soft start , braking, reversing , torque limiting and variable rpms .

 

[LD1]

The VFD gives soft start , braking, reversing , torque limiting and variable rpms .

None of which I think are really beneficial for a mere 5hp lathe.

Reversing.....lathe does that.
Braking.....lathe does that
Soft start......the motor starts under no load. Gear head engaged with clutch.
Variable speed .....lathe does that. Sure it isn't infinitely variable.....but more than sufficient.

 

[prichard]

I'd think but not sure that a new 1ph motor will be the most efficient. To me that is also the simplest and has least parts to break.