# To VFD or to not VFD



## sdhorton (Apr 9, 2021)

Hi, thanks for letting me play, I have a South Bend 14" lathe with a 3 hp 3 ph motor with max amperage of 10.5 amps. 
Like many others I need to power this from a 220 single source. I have looked at RFCs and SFC and FVDs until my head is spinning. Have any of you done this and can you make specific recommendations as to what power converter I should use and why? This lathe has a variable speed system in it, it is like a reeves drive, or like a snow machine clutch set up. That and a lube pump in the head need 110v AC that should come off the power source ONLY when the motor is turning or you will damage the vari-drive.


----------



## Ulma Doctor (Apr 9, 2021)

You could easily use a single phase to 3phase VFD and use it at 60Hz
The 3phase motor would work as intended, the reeves drive would be used for variable speed
You could ramp the acceleration and deceleration to your needs too

i put a 3hp 3 phase motor on my shenwai 1236. It greatly improved the performance

a RPC is easy to make but it would require a 5hp idler motor to operate efficiently

a static converter is even easier to construct, but you will not not develop the entire motor output . You’ll loose about 1/3 of the motor hp potential.
Most times this is not an issue with sparsely used equipment under light to moderately loaded operational conditions

the VFD is the best option for the price, but there is some knowledge to gain to setup if you are not used to control devices

here is my 3hp conversion on the shenwai 1236


----------



## Dabbler (Apr 9, 2021)

+1 to everything Ulma Doctor said above.


----------



## graham-xrf (Apr 10, 2021)

Listen to @Ulma Doctor !
Get the VFD!
 A little search in this forum will find the most complete discussions, and explanations of the new technology that is hidden behind the little three-letter reference.


----------



## rabler (Apr 10, 2021)

If you’re using a vfd, some have a relay contact that can be set to close on running which could be used for the lube pump, probably via a small contactor.


----------



## .LMS. (Apr 10, 2021)

VFD for sure.   I love having one.   I have not heard of anyone regretting the decision to get one.


----------



## kcoffield (Apr 10, 2021)

sdhorton said:


> This lathe has a variable speed system in it, it is like a reeves drive, or like a snow machine clutch set up.


Since your lathe already has mechanically controlled variable speed, you might consider installing a Rotary Phase Convertor. That way you could power other three phase machine additions to your shop, but a VFD would likely be less expensive if you don't foresee any future need. I can say my RPC was one of my best shop investments ever. There's a lot of great three phase equipment available, usually for a fraction of the cost of single phase machines.

Best,
Kelly


----------



## epanzella (Apr 10, 2021)

What is wrong with using the VFD and the variable speed pully system to compliment each other and extend your speed envelope? My mill had a speed range of 120 to 2500. When I installed my VFD I left the multiple pulley system and when combined with the VFD gave me a speed range of 30 to 5000 rpm. As far as powering the lube motor my VFD had some extra contacts that I didn't use and if I remember correctly they were make and break contacts for running other accessories.


----------



## G-ManBart (Apr 10, 2021)

.LMS. said:


> VFD for sure.   I love having one.   I have not heard of anyone regretting the decision to get one.


I won't call it a regret, but I took the VFD off my Bridgeport mill and went to an RPC and I like the setup better.  I like being able to use the factory F/R switch, and the wiring for the light, DRO and power feeds comes off the step-down transformer, so it's a simpler setup.  The bonus is the RPC is quieter than the VFD was...especially because I have the RPC 20ft away.

The cherry on top was that after I made the switch I added three more 3-phase machines and I didn't have to spend another $1K on decent VFDs.


----------



## G-ManBart (Apr 10, 2021)

There is a really nice North American Rotary 5hp RPC in the classified section here listed for $275....even with expensive shipping to you it would be less than the $500 they go for on Amazon.  I have the 7.5hp version and it's really nicely made.


----------



## matthewsx (Apr 10, 2021)

Hi and welcome.

If you're new and just want to get up and running ASAP I'd recommend a static or rotary phase converter. To get the most out of a VFD conversion you really need to rewire the machine, while it's possible to just run off a VFD at 60hz the phase converters are truly simple and cheap.

I'm running my 13x40 lathe off a static converter and it works fine. At some point in the future I may retrofit a VFD I don't feel the need for it yet. I do have one on my other lathe but it didn't have any electronics to start with so it's only the motor to worry about.

John


----------



## BladesIIB (Apr 10, 2021)

I agree with everything said so far about going the VFD route. 6 months ago I did not even know what one was and now I have a PM 1440TL Lathe running on one and could not be happier. Thanks to mksj for all his help in teaching me the process. Below is a video of all of my learning that may help you get your head around a VFD and what you are re wiring on your machine to have it all work. 

As for why?
Controlled start up speed 
Controlled stopping speed 
Fine tuning of speed during a cut to reduce chatter or speed up while facing for a better finish, or vary speed to get chips to break

Those are some benefits off the top of my head.


----------



## G-ManBart (Apr 10, 2021)

BladesIIB said:


> Fine tuning of speed during a cut to reduce chatter or speed up while facing for a better finish, or vary speed to get chips to break.


His machine already has an infinitely variable speed drive (fairly rare on a SB), so he will have the ability to fine tune during a cut either way.


----------



## BladesIIB (Apr 10, 2021)

G-ManBart said:


> His machine already has an infinitely variable speed drive (fairly rare on a SB), so he will have the ability to fine tune during a cut either way.


Fair enough. I was not familiar with the drive so did not know if you could adjust while running or not?  Like with facing a large part I actually turn up the speed as it gets to the center to try and keep the actual cutting speed up while the diameter gets smaller. Will still get the controlled starting and stopping.


----------



## .LMS. (Apr 11, 2021)

G-ManBart said:


> His machine already has an infinitely variable speed drive (fairly rare on a SB), so he will have the ability to fine tune during a cut either way.


G-Man - what you say is of course true.   But using a potentiometer to adjust speed during an operation (while perhaps even using your other hand to move the compound) is far easier than trying to muscle a reeves drive.


----------



## BGHansen (Apr 11, 2021)

I have two three-phase machines (Bridgeport 2HP and DoAll 16" band saw) both running on static phase converters. I've had no issues with the 1/3 reduction in horsepower, but I'm from the school "if I break it, I have to fix it" and run on the conservative side. The BP had the phase converter on it when I bought it.  Worked fine so I went the same route on the DoAll.  Really easy install on the saw, ran a 220V line to a DPDT push button switch mounted to the saw. The four wires from the saw dropped into a terminal block in the phase converter and it was up and running.  The 3/4-1 1/2 hp phase converter was around $45 off eBay.

That being said, guys with vfd's love them for the added controls.  Instant variable speed, braking, reversing, etc.  They take more time for the initial set-up, but give you more features down the road if you need/want them.

The RPC puts the machine(s) in "as-designed" by the factory mode with no reduction in power like the static convertor.  You'll see posts here with more pros than cons.  Cons are the noise from the idler motor, more involved in the initial set-up, worry about leaving it running when leaving the shop, etc.

Both of my machines have Reeves-type variable speeds.  Speed changes are a spin of the handwheel instead of a quick turn of a pot (VFD).  It takes a little more time, but hasn't been enough of an inconvenience to me to switch over to a VFD (yet).

Bruce


----------



## G-ManBart (Apr 11, 2021)

.LMS. said:


> G-Man - what you say is of course true.   But using a potentiometer to adjust speed during an operation (while perhaps even using your other hand to move the compound) is far easier than trying to muscle a reeves drive.



The setup South Bend used is actually quite different from most of the other similar systems.  They put a hand wheel on the front of the machine, at waist height in line with the headstock, so it shouldn't be too hard to manipulate while doing something with your other hand unless the saddle was out there a ways.  Not as easy as turning a knob, but not too bad.


----------



## mksj (Apr 11, 2021)

If the reeves drive is working then one can go either route, in many cases the mechanical drives have failed and then a VFD with a larger motor is used. As others have noted the VFD allows controlled acceleration and deceleration and for a single machine is a bit less expensive than an RPC. They do take a bit more work/costs to install them properly and maintain safety.  When using a VFD with a mechanical speed drive, I still recommend using the mechanical speed adjust for major changes, if left in one speed it will wear unevenly.


----------

