# Remotor or Rotary Phase Converter



## fltenwheeler (Jul 20, 2016)

Hi

I will be taking delivery of a replacement lathe shortly. It is 3 phase with a variable speed belt drive. I would like your thoughts on a rotary phase converter or remotor with a single phase motor. The cost is the same for ether option.

Thanks

Tim


----------



## SmithDoor (Jul 20, 2016)

Just get the motor 
The draw back to rotary phase converter it will run all day cost money to run just rotary phase converter 

Have try both ways

Dave


----------



## ninefinger (Jul 20, 2016)

Why not use a Variable Frequency Drive (VFD)?  Many are available as single phase input and 3 phase output, with the added bonus of variable speed (frequency).  As long as the motor is a 220 to 250V motor you should be able to find a VFD to drive it.

I've got a 3hp on on my mill and a 1 1/2 hp on my lathe - absolutely love them. Single phase, 60Hz 220VAC in, 3 phase 220V out (15-400Hz)
Mike


----------



## TRACKWELDER (Jul 21, 2016)

Check Surplus Center, they had the converters pretty cheap, and sometimes they have pretty good prices on electric motors


----------



## rklopp (Jul 21, 2016)

I'd choose VFD unless you have more than, say, four machines needing 3-phase conversion. The VFD gives you motor protection, speed control, logic, and quietness all in one package. I have four VFDs in my shop. The manual mill has two: one for the spindle motor and one for the feed motor. The Chipmaster lathe has one, and the bandsaw has one. Only the bandsaw regularly uses the variable-speed capabilities of the VFD. The other machines still have functional mechanical variators. Nonetheless, I don't need to worry about motor starter heaters or relay logic, and I could easily integrate the motor controls into the existing machine pushbuttons, eStops, etc. I do use the VFD speed control occasionally to lower the spindle speed to a crawl, such as when winding springs.


----------



## Wizard69 (Jul 22, 2016)

fltenwheeler said:


> Hi
> 
> I will be taking delivery of a replacement lathe shortly. It is 3 phase with a variable speed belt drive. I would like your thoughts on a rotary phase converter or remotor with a single phase motor. The cost is the same for ether option.
> 
> ...




What size three phase motor?   Generally below 3HP Variable Frequency Drives (VFD's) are very economical for converting old equipment.  Now you are indicating a variable speed belt drive which is useful even with a VFD.   Even with a good VFD and motor it is still useful to be able to do belt reduction to get more torque.


----------



## fltenwheeler (Jul 22, 2016)

Wizard69 said:


> What size three phase motor? Generally below 3HP Variable Frequency Drives (VFD's) are very economical for converting old equipment. Now you are indicating a variable speed belt drive which is useful even with a VFD. Even with a good VFD and motor it is still useful to be able to do belt reduction to get more torque.


 
It is a 2HP on a Rockwell 14"x30" lathe. 

Tim


----------



## TRACKWELDER (Jul 23, 2016)

Depending on mount you can get a single phase motor for about the same price as a phase converter, the thing to remember is your motor will only make about 2/3 of its hyorsepower, if possible I would remotor


----------



## Wizard69 (Jul 23, 2016)

fltenwheeler said:


> It is a 2HP on a Rockwell 14"x30" lathe.
> 
> Tim




At 2 HP you should be able to find a cost effective VFD.   Unless you go the DIY route, a rotary phase inverters isn't exactly cheap.   The only issue you might run into is that drive will likely require 220 VAC input you should be able to find a drive that can take single phase in for that HP range.  Automation direct for example has a drive, GS2, that starts at around $250.   

There are additional expenses such as a panel box, wire, fuses and etc.    Those are expenses though that any solution requires.    You could look for a drive that comes with an enclosure which obviously costs more 

I just wanted to point out VFD because for whatever reason people don't seem to know that they are very cost effective these days.   Below 1HP they compete with the old cheap DC drives very well, often the "better" solution.   

Beyond all of the above VFD's offer features that aren't available with rotary converters.  This includes soft start, variable speed, electronic reversing (some models), and other features.  

Ultimately the choice is yours.  VFD's are just one of your options but they do seem to be overlooked often by people buying industrial equipment.


----------



## BobsModels (Jul 23, 2016)

Hi

I have both systems.  I have used VFD's for over ten years.  I have them on two mills a 1HP and 2HP.  I have one on a 2HP 12" lathe.  I put one on my 7.5HP air compressor, it is set for a  soft start and only run at about 1/2 the RPM so minimal noise.   The variable speed feature is real nice.  As for the power reduction I have really not noticed it, on the 12" lathe I took a cut that snapped a 3/8" HSS cutter as an experiment.  Given I would never take cuts like that anyway for me the power reduction is a none issue.  I also have a 10HP commercial rotary that powers any thing that has two motors ie Norton Grinder, or two speed motors ie my drill press.

So from my experience I needed multiple solutions.  Good Luck setting everything up and making chips.

Bob

Bob


----------



## Gordon (Jul 23, 2016)

I have been running on an idler motor started by capacitors similar to:

http://www.k3pgp.org/3phconv.htm

The parts for the capacitor start circuit are under $100.

Old used 3 phase motors are cheap. The old cast iron frame motors in the 3 HP range run in the $25 range in my area.

I just start the idler motor with the capacitor circuit and then have the three phase circuit wired to various receptacle around the shop. At this point I am mainly running a 2 HP lathe and a 1 1/2 HP mill. The idler motor draws almost no current when just idling and when I start the other machines it is instant start. Now I am running just my home hobby retirement shop but I ran a lot more when I owned and operated a metal fabricating shop for several years before I could get 3 phase power.

I made a capacitor start box as above using banks of capacitors hooked to switches so that I could use the same converter for various horse powers. I probably made and sold a dozen of them. Actually it is not necessary to have the banks of capacitors. Just get an idler motor larger than your largest machine motor and everything starts and runs just fine. 

For a home shop it is possible to just run an idler motor with a sheave on the shaft and kick it over to get it started. Once it is started it keeps running. I did that on my home shop when I was just using it occasionally before I retired. 

As an interesting side note. When I started the fabricating shop 3 phase power was about 1/2 mile away and to run the three phase to the shop would cost me several thousand dollars. Finally when I had several employees it was getting to be kind of a problem so I looked into how much it was going to cost me to run in the three phase. I found out that they could upgrade my existing service for free. Had I know that I would have upgraded the week after I put in the single phase.


----------



## rklopp (Jul 23, 2016)

TRACKWELDER said:


> Depending on mount you can get a single phase motor for about the same price as a phase converter, the thing to remember is your motor will only make about 2/3 of its hyorsepower, if possible I would remotor


That is not true. Source?


----------



## Wizard69 (Jul 23, 2016)

rklopp said:


> That is not true. Source?




It all depends upon how you decode the sentence.  I think what he is saying is that you loose horse power when running off a simple 3 phase rotary converter.    This is generally true.


----------



## Robert Murphy (Nov 22, 2018)

rklopp said:


> I'd choose VFD unless you have more than, say, four machines needing 3-phase conversion. The VFD gives you motor protection, speed control, logic, and quietness all in one package. I have four VFDs in my shop. The manual mill has two: one for the spindle motor and one for the feed motor. The Chipmaster lathe has one, and the bandsaw has one. Only the bandsaw regularly uses the variable-speed capabilities of the VFD. The other machines still have functional mechanical variators. Nonetheless, I don't need to worry about motor starter heaters or relay logic, and I could easily integrate the motor controls into the existing machine pushbuttons, eStops, etc. I do use the VFD speed control occasionally to lower the spindle speed to a crawl, such as when winding springs.


I am in the same boat with a 575volt chipmaster. My intention was to connect a 3hp vfd to the line input of the control box at the back and change out the motor to the same voltage as my 230v single phase service. I'm not up on vfds  and what you can and cannot connect to them, but I was told that all the vfds want to see on their o/p is a direct connection to the motor, nothing else!  I really don't want to hack up the electrics or bypass them. rklopp, can you tell me exactly what you have setup on your chipmaster? Are you running all of the original equipment.


----------



## SmithDoor (Nov 22, 2018)

Build a rotor phase simple
When my shop I  did both 

Dave


----------



## rklopp (Nov 23, 2018)

I have a 240-V VFD connected directly to the original Brooks Crompton motor, with no disconnect between the VFD and motor. The rotary forward/off/reverse switch controlled by the red ball handle above the headstock is wired to the VFD remote control inputs. The coolant pump motor is abandoned in place. The worklamp is powered separately via a normal wall receptacle.

I have two mills that were originally 575-V. On one, I removed the 575-V motors and replaced them with 240-V 3-phase motors driven by separate VFDs. On the other, I built a 575-V step-up transformer system to power the mill from my 240-V phase converter. That mill has kept its original electrical system. 

Unless you foresee more 575-V machines or have a strong yearning to keep the Chipmaster all-original, if I were in your shoes, I'd swap the motor to a 240-V, 3-HP, 3-phase, 4-pole motor and drive it with a 240-V VFD wired directly to the motor, and reconfigure the switches to control the VFD. YMMV.


----------



## Ironmanaz (Nov 23, 2018)

No one mentioned the fact that on (especially belt) lathes, you get a better finish with  3 phase.


----------



## joco-nz (Nov 23, 2018)

If the 3 phase motor in question is not dual voltage you can still go the VFD path. There are units that take 220/230V single phase in and supply 380V 3 phase out.  You do need to get double the wattage though. Eg 1HP motor needs 1.4kW or better VFD. 

The VFD path  definitely has many advantages as other posters have pointed out.


----------



## rklopp (Nov 23, 2018)

Ironmanaz said:


> No one mentioned the fact that on (especially belt) lathes, you get a better finish with  3 phase.



This is an old wives’ tale, Snopes-worthy.


----------



## Chiptosser (Nov 23, 2018)

I have built many rotary converters,  they can be simple or they can be more involved.
Another solution for you to consider, if you are in the states.  There are a couple of outfits selling a unit that you just ad in line of your wiring.
One unit called Phazpak, lots of info online.  They are in Indiana. very simple to install.
Wire the motor for your voltage and power it up.
Or you can use the phazpak on a idler motor and power multiple motors on other equipment.


----------



## SmithDoor (Nov 24, 2018)

Never seen that I have  run single and three phase lathes.
If have bad bearings out of balance motor may give you a bad finish but this true with both phases

Dave 



Ironmanaz said:


> No one mentioned the fact that on (especially belt) lathes, you get a better finish with  3 phase.


----------



## Gordon (Nov 24, 2018)

From my experience having an idler motor is the key to having a smooth 3 phase experience. I have read that you only have about 2/3 of the HP using a phase converter. I do not know if that is true but for most home shops we are not using anything close to the maximum HP. We are not trying to do heavy duty production work. Taking three cuts on a lathe instead of two is not an issue in the home shop. Perhaps with some of the smaller machines others are coming close to maximum. I doubt that my South Bend lathe and Excello mill are anywhere near capacity the way I use them.


----------



## mu38&Bg# (Nov 24, 2018)

Static(solid state) phase converter or a 3PH motor running with capacitors on 1PH results in less power output than nameplate rating. (phazpak and others as mentioned above)

A 3PH motor running from a rotary phase converter(idler motor) or VFD will make full power when properly sized and configured.

Someone mentioned VFD's with 230V input with 380V output. There also exist VFD listed as 115V input with 230V output. While they do work, cheap ones do not output full 230V so you lose some power.


----------



## Chiptosser (Nov 24, 2018)

Robert Murphy
First off, in your situation you first need to check your motor for wiring options.
If you can not change wire configuration, you will have to change the motor or use a transformer.
Look at the spec. tag on the motor for available wiring  options.

I am in the same situation as Gordon. multiple horse powers on multiple machines. from 3/4 hp  to 15 hp.
I have capacitor bank for the very large loads, to no caps. for the smaller motors. 
The capacitors are to balance the loads between the 120v per line feed. 
Yes, this is a 220v single phase system.

This is always a big decision for someone starting out.
 If you do not plan on getting any more machinery,  VFD's can be very nice, especially a drill press where you want to vary speed for different drill sizes. 
One thing that you need to know about VFD's is that older motors, it all depends on the use, don't play well together. You can get humming and over heating.  The VFD can over load if you don't size it properly.  You do have to set parameters in the control for it to work properly.  If you don't like to mess with that sort of thing, you will have to get somebody who understands what is needed.
It is fairly easy but if that is not for you, so be it.  
All the formation is  on line and you can check it out for your selves and decision.

fltenwheeler 
Is your lathe a Delta Rockwell, variable belt speed lathe?  The one with the variable speed lever on the lower left. 
Or is the v/speed near the gear changer?


----------



## Paul_C (Nov 24, 2018)

> It is a 2HP on a Rockwell 14"x30" lathe.
> Tim


Unless you already have a 2hp single phase motor that would fit I would recommend a single to 3 phase VFD.  It will cost less and would be perfect for that application. A few things to consider. A VFD will allow the motor to make full power. A single phase motor of the same rated power will not have the same start torque as a 3 phase. Unless you have a monster rotary phase converter the machine motor will only produce 2/3 to 3/4 of it's rated HP.

I ran a 1 hp Bridgeport and a 10" South Bend lathe with the original 3/4hp for years on a rotary converter. I never had a problem bogging down the Bridgeport but the 3/4hp on the South Bend certainly was weak. Now I can make some serious chips on the South Bend. So many advantages to using a VFD such as adjustable acceleration, deceleration and DC braking.


----------



## Robert Murphy (Nov 24, 2018)

rklopp said:


> I have a 240-V VFD connected directly to the original Brooks Crompton motor, with no disconnect between the VFD and motor. The rotary forward/off/reverse switch controlled by the red ball handle above the headstock is wired to the VFD remote control inputs. The coolant pump motor is abandoned in place. The worklamp is powered separately via a normal wall receptacle.
> 
> I have two mills that were originally 575-V. On one, I removed the 575-V motors and replaced them with 240-V 3-phase motors driven by separate VFDs. On the other, I built a 575-V step-up transformer system to power the mill from my 240-V phase converter. That mill has kept its original electrical system.
> 
> Unless you foresee more 575-V machines or have a strong yearning to keep the Chipmaster all-original, if I were in your shoes, I'd swap the motor to a 240-V, 3-HP, 3-phase, 4-pole motor and drive it with a 240-V VFD wired directly to the motor, and reconfigure the switches to control the VFD. YMMV.


Many thanks for the information...I was wondering about the feasibility of consolidating the f/r switch with the vfd remote 
Controls. Knowing that pushes me toward new vid+motor combo. Was the step-up transformer difficult to build?


----------



## Robert Murphy (Nov 24, 2018)

Chiptosser said:


> Robert Murphy
> First off, in your situation you first need to check your motor for wiring options.
> If you can not change wire configuration, you will have to change the motor or use a transformer.
> Look at the spec. tag on the motor for available wiring  options.
> ...


The lathe is a Colchester Chipmaster with a variable speed (mechanical unit )called a variator 35-3000 rpm. The motor drives the variation via flat clogged belt which then in turn drives the headstone.  I would like to keep it original but want to keep cost below $1k. The motor Is 550v so the only other option is two-fold, phase converter & step-up transformer. I would build a rotary phase system but the used motor market sucks in my area!


----------



## rklopp (Nov 24, 2018)

The transformer setup was not difficult to build, but I have experience with code requirements and running conduit. The hardest part was lifting the heavy transformers onto the wall mounts! Beware you are dealing with lethal voltages, so use wiring, switches, and other appurtenances rated accordingly. I have attached a diagram of my setup. The RPC shown in the diagram has been replaced by a PhasePerfect unit. That makes no difference to the open delta transformer setup. More info here.

Key safety aspects include (but are not limited to):  (1) grounding one corner on the high side, or else the three phases could theoretically float to higher voltages and might not blow a fuse in case of a ground fault; (2) having no fuse in the grounded leg, or else in the case of certain phase-to-phase faults, the fuse in the grounded leg might open while leaving the "high" leg fuses intact and therefore leaving the "high" legs live and dangerous.


----------



## Gordon (Nov 24, 2018)

I am wondering if there is a problem with using a VFD which is oversize. In other words if I am running a 1 HP motor would it be a problem using a 3 HP VFD? 

Also is there a proper way to run multiple motors from one VFD? Size the VFD based on total HP of all motors or just the largest if there is a possibility of running more than one at a time? Run an idler motor and size the VFD on the idler motor size?


----------



## Robert Murphy (Nov 24, 2018)

Sorry about typos as I was using a tablet that I had just flattened and spell check was running rampant...I meant "Variator"  not variation and 'headstock" not headstone! Had a chuckle over that one!


----------



## rklopp (Nov 24, 2018)

"I am wondering if there is a problem with using a VFD which is oversize. In other words if I am running a 1 HP motor would it be a problem using a 3 HP VFD? "

There can be a problem dialing down the current limit for motor protection, depending on the VFD. I have a 3-hp Teco VFD for which I am unable to set the motor current limit down to the nameplate current rating of a 3/4-HP motor. I suggest you check the motor nameplate full load amps (FLA) and the manual for the VFD you have in mind.


----------



## Paul_C (Nov 24, 2018)

> I am wondering if there is a problem with using a VFD which is oversize. In other words if I am running a 1 HP motor would it be a problem using a 3 HP VFD?



Not at all, in fact you are better off oversizing a bit. I got two 3hp Hitachi VFD's for my lathe and mill. I have never seen a VFD where you can't set the motor ratings, but I guess they can exist.



> Also is there a proper way to run multiple motors from one VFD? Size the VFD based on total HP of all motors or just the largest if there is a possibility of running more than one at a time? Run an idler motor and size the VFD on the idler motor size?



It's possible, you just add up the motor ratings or size the VFD for the largest motor But is it worth it. What VFD's don't like is a load switched on. You also won't benefit from sensorless vector which requires the VFD to be autotuned to a particular motor. 

Many of the newer VFD's have a second motor parameter so you could program them for different machines. But by the time you build some complicated scheme to switch the output and controls your money would be better spent on a dedicated VFD for that machine. Then you can program all the custom parameters such as accell, decel, braking, jog for that machine. On my Bridgeport I set the first motor data for 60hz with a fast acceleration and maximum deceleration so I can instant reverse. Then I set the second motor parameter for 90hz with a mild acceleration and deceleration. Not all motor parameters such as jog speed can be set to a second motor profile. I even fiddled with the carrier frequency to get rid of the ringing a certain speeds.


----------



## David Shealey (Nov 25, 2018)

rklopp said:


> This is an old wives’ tale, Snopes-worthy.


No.  I have a JET 13X40 gear head lathe, when I got it was surprised at the finish I was getting, read a few things on line about this being a problem with a single phase motor. Did not change the motor, but changed the belt to a Fenner "link belt", finish improved greatly.  This was mentioned on a few forums as being almost as good as switching from a single phase motor to three phase. In my case, it was good. The belt on this lathe is pretty short, so the stiffness of it transmits the vibration of the motor very well. The Power Twist belt has enough stretch to even it out.  I may one day put a three phase motor on the lathe as I have a rotary phase converter on my milling machine.


----------

