Are Good Used Lathes Like Unicorns?

[Ischgl99]

Yes you definitely have more control and a host of other things you can do depending on how you see up your VFD and the programming but with the VFD but you lose some Power or at least I did with the ones I had

Were you running your 10hp motor on a 10hp three phase VFD with single phase input? If so, you would not have full power, it will be approximately 40% less than the VFD rated power. My motors are much smaller and I can get single phase input VFDs that give me full power at rated size. I think they are available up to 3hp, but someone might be making a larger one now.

 

[Ultradog MN]

An RPC will have more parasitic loss than a VFD. One of those damned if you do, damned if you don't kinda things.
I checked it with an amp meter and it uses 3.69 amps with no load on it.
On the other hand, I only have about $150 in it and as we talked about earlier it does allow the use of several machines though not all of them simultaneously of course.
One thing I did with mine is I put the idler motor outside behind the garage.
I poured a concrete base and mounted it to that.
I can barely hear it running and having it out there doesn't use any indoor real estate.
Am real glad I did that.
I was going to build an enclosure for it but the bucket seems to suffice and I may just leave it that way.

 

[DAM 79]

So my biggest machine has a 10 Hp motor my rotary phase converter is a ADX -20 so I have a 20 Hp motor I see no loss in power at all

 

[DAM 79]

And I saw a noticeable difference in all my machinery because when running a VFD your losing power at some percentage every VFD is different so if you have a 1Hp three phase motor and put a VFD on it your not getting that 1Hp three phase motors full potential your losing some percentage of that I think around almost a third of that

 

[DAM 79]

Also on this topic one could make there own RPC pretty cheap all you need is a 3 phase motor there are many videos on YouTube on how to wire one up and they can be had pretty cheap from the local scrap yard

 

[Ischgl99]

And I saw a noticeable difference in all my machinery because when running a VFD your losing power at some percentage every VFD is different so if you have a 1Hp three phase motor and put a VFD on it your not getting that 1Hp three phase motors full potential your losing some percentage of that I think around almost a third of that

That’s only true if the VFD is three phase only input. If it was designed for three phase or single phase input, you will get full rated power up to the capacity of the VFD.

 

[MtnBiker]

Plus one for the American Rotary Phase Converter!!!! .... Now with all that being said I did not buy mine New I got it Used and I was Very Lucky the previous owner never hooked it up or used it and I pretty much Got a smoking deal($1200 bucks)

So...we now have a RPC unicorn sighting

 

[DAM 79]

So...we now have a RPC unicorn sighting

Yes I have been very lucky in my quest to have a little hobby shop that is for certain and it just goes to show that they are out there !!!

 

[mksj]

And I saw a noticeable difference in all my machinery because when running a VFD your losing power at some percentage every VFD is different so if you have a 1Hp three phase motor and put a VFD on it your not getting that 1Hp three phase motors full potential your losing some percentage of that I think around almost a third of that

I think you must be thinking of a static converter, VFD's do not loose a performance percentage at the motor base frequency unless improperly matched or the programmed parameters are incorrect. If anything you get better operating performance when programmed for SLV/feedback to the VFD. My recollection is that an RPC delivers ~90% of the performance of true 3 phase for motors. There are also significant costs associated with an RPC if you add a sub-panel, breakers and wiring. VFD's these days tend to be more economical for individual machines 3 Hp and under, above that point the price starts to swing toward an RPC. The choice is also one more of function and if you need the VFD's additional motor control vs. you just need 3 phase.

 

[Ultradog MN]

The choice is also one more of function and if you need the VFD's additional motor control vs. you just need 3 phase.

Well said.
Things like variable speed and over speeding the motor on an older lathe are nice and can be accomplished with a vfd but not an rpc.
Things like DROs and the ability to cut both metric and SAE threads are also nice.
I think it depends in your needs, wants and maybe your comfort with more modern technology.
On the other hand, my old lathe has 16 reliable speeds and really Nice dials on my compound, cross feed and carriage. I am very comfortable with using that old technology and don't see myself needing to upgrade it beyond its original capability. I'm an old school fool so just make it run and I will be happy.