New motor or phase converter?

I have an opportunity to get a nice southbend lathe. However, it has a three phase motor. I don't have three phase electricity . Which is better to get a single phase motor or to get a phase converter? Which is more expensive? How hard is it to remove and replace the motor? The motor is inside the stand. I have a Toyota Tacoma and the lathe weighs a bit over a thousand pounds. Any warnings?
Many Thanks Bob

I would suggest a VFD and control the VFD with your existing lathe controls, second a rotary phase converter which you can build or buy and then lastly a single phase motor.

As for the truck I wouldnt worry about the weight so much but secure the lathe very well. Like with tie straps to back bumber and then frame between cab and bed if possible.

shop ebay for vfds (ac tech is us made). 150,200 tops. once you have one, you wont use any other method. Program start speed up, decellerat speed, top speed, program 5 different speed presets. I just pulled my single phase motor out and put a 3 phase in.

Swaping out to single phase is usualy easy.
The smaller SB lathes used NEMA 56 frame motors, and that is a very common motor frame to encounter new or second hand. If its a 56 frame (look at the motor tag) the change out is just a bolt in and rewire routine.

VFD on 3phase is also nice, especialy on a SB lathe. It allows you to run the machine at any speed desired. Also, the cost is not that much different in cost than a new high quality motor.
There will be some power loss issues and more electrical stuff to learn about. Also watch the low end on the motor speed, particuarly if you have a fan cooled motor. If the fan does not spin fast enough, then the motor will not cool itself properly.

Phase converters
This is a good way to go if you anticipate buying other 3 phase equiptment (a mill). With a ROTARY phase converter you can power a lot of different machines, but the cost of a comercial one is in VFD country. The upside is that plans can be found all over the net and they are not hard to scrounge up parts for.

This response is one of the reasons why this web site is so great. A wealth of information here. The lathe in question was on Ebay and it went for considerably more than I had hoped it would go for. To all who responded I made copies for my notes and I'll use them if I ever acquire a 3 phase. Thanks Bob

Bob,

All of the above is good advice, but the one thing that I would avoid is a static phase converter as I have one on my 16/24 South Bend and don’t like the power loss. I also have a friend that has a 16” SB with a different brand of static phase converter than mine and he is also down a bit on power. I am getting ready to build a rotary phase converter because I have just bought a Hardinge mill and will need 3 phase for it and will also have it to use with the SB and get rid of the static phase converter that is on it now. I think that static phase converters have their places, but I don’t like mine as in the aforementioned application.

Another option that hasn’t been mentioned is DC. I have converted my drill press to DC by utilizing a 1.5 HP DC motor and controller salvaged from a tread mill and it works great. I added a DPDT (dual pole / dual throw) switch to it and did it all for about $25.00 ($20 for the old tread mill - $5 or so for the DPDT switch) As per mounting match up --- the DC motor happened to mount directly to the motor mount base on my drill press. I just bought another old tread mill that runs good for $10.00 and I believe that it has a 2 HP DC motor. Obviously not all tread mills have DC motors and if you should decide to go this route, you can check these matters out before buying it and make sure you know what you are doing in wiring it up.

Over & Out ----- Dan

For the edification of this old lurker newbie.Just what is a VFD. And not knowing what it is or does, why would it be a benefit for me to buy and install one?
In other words "tell me more"??

"Just what is a VFD. And not knowing what it is or does, why would it be a benefit for me to buy and install one?"

VFD stands for Variable Frequency Drive. The electricity in your home shop is single phase, and 50 or 60 Hz. The right VFD (there are many types) will take in 220V single phase, and output 220V 3-phase, and let you adjust the frequency higher or lower than 50/60 hz. This allows you to run that 3-phase motor on your lathe or mill, AND gives you variable speed adjustment, beyond what the gears or pulleys will let you do. That's it in a nutshell.

Jeff

Thanks for the nutshell. Wish I had known about VFDs about 1o years ago. Someone gave me a warehouse to clean out with about 20 3phase motors in it. All went to scrap.

"VFD stands for Variable Frequency Drive."

All-electronic VFDs, which are the most popular today, consist of three independent parts:

1) a "converter" section, which accepts line-level voltage of almost any alternating current frequency, either single- or three-phase, and converts this to high voltage direct current, usually 325 volts for a 240 volt VFD or 650 volts for a 480 volt VFD [ * ] , and

2) a "bulk storage" capacitor section, and

3) an "inverter" section, which accepts the high voltage direct current, and converts this to three-phase alternating current, usually from nearly zero Hz to 120 Hz, with this alternating current being a series of high voltage pulses which simulate the sine waves usually found in true utility power.


[ * ] 120 volt VFDs exist, and these often have "voltage doubler" type converters, so as to utilize the existing 325 volt sections of a 240 volt VFD.

Bob,
If you're trucking it home in one piece, a word of caution. ANY lathe is very topheavy. More important than preventing it from sliding, is the definite chance of tipping. Lash the TOP of the lathe to both sides of of the truck or even to four corners. Better safe than very sorry.
Chaz

I vote VFD for the above reasons. All the advise is right on. I would stay away from a static phase converter.

Grits

I have an idler on the Bridgeport and a static on the 16/24. The 16/24 has a 5 hp motor, so losing a third leaves more than the original 3 hp. The 2 hp idler is started with a jerk rope, provides full power to the small power 2j. If you can accept a 1/3 loss in power, I don't see anything wrong with a static. I've got an extra 5 hp motor; some day I'll put it on the static and use it to run both. Just haven't got around to it.

Dan Wyatt mentioned using a DC motor, and I have done just that on different machine tools over the years. The only thing you need to keep in mind is that DC motors are constant torque, while AC motors are constant horsepower. This is really only a problem at very low speeds, and for cuts that need to run at a very precise speed. DC motors can bog down noticably , or even speed up, under high or sudden loads. Tachometer feed back DC drives will help, but those are for high $ applications. Three phase motors are more efficient than single phase, so I always recommend three phase. The rotary phase converter is an expense, but the results are hugely better. A three phase motor armature is being driven all the time while the single phase armature is "floating" for much of the phase cycle. http://www.phase-a-matic.com/ This site has good info. And don't worry about changing out the motor. NEMA sizes are reliably uniform. Good luck.

Bob, I bought a 9" & Heavy 10" from a college about 200 miles away. Rather than try to wrestle with them in my pickup, I rented a metal floored trailer from U-Haul at the college town. Both lathes fit in it and when I got home, we were able to slide them out and lower the end onto the floor using long metal tamping bars and or a length of square tubing as levers. The trailer bed was close enough to the floor to make it a pretty straight forward job. People forget how efficient a lever is. I moved the Heavy 10 across my shop 4" at a time to get it in position by myself with a 6' tamping bar.

I vote vfd. I just upgraded to a vfd and I have a good roto phase. I like the fact that you can make it vari-speed as well as single phase.I run 1 phase in the top and 3 phase out the bottom. Very easy to hook up, If you can hook up a light switch, you can hook this thing up!
In my case, i have an 11 inch Rockwell Lathe, I contacted AnythingPC who has a GS2
vfd for around 119.00. The unit about fits in my hand and has a remote control you can take off the unit so you can hold it in your hand and control the speed.
Yes, the first one they sent was bad, just my luck! BUT they have great backup support and send another asap. It works fine. Good people
Just my 2 cents.....geneB

This has been a wealth of information. Thank you to all. The lathe in question was sold at considerably higher than I wanted to pay. Funny thing the price jumped by about 500 dollars in the last two minutes. I will however look for a VFD should I ever get my hands on a three phase. Thanks, Bob

"The only thing you need to keep in mind is that DC motors are constant torque, while AC motors are constant horsepower. This is really only a problem at very low speeds, and for cuts that need to run at a very precise speed. DC motors can bog down noticably , or even speed up, under high or sudden loads. Tachometer feed back DC drives will help, but those are for high $ applications."

The Monarch 10EE has used dc drive from the late 1930s to the late 1980s.

Just about every variable speed motor is constant torque below the motor's "base speed" and is constant horsepower above this "base speed".

Dc motors, included.

In the case of the 10EE, the drive system is completely open loop, although there is I-R compensation.

Machines made after 1949 have an electronic drive; machines made before about 1952 could have a Ward-Leonard (motor-generator) drive. There was a several year overlap in the availability of the two drive types, but both used the same, or a similar dc spindle motor.

There is precisely variable speed from nearly zero to 4,000 rpm, and no surging or other abnormalities.

A dc motor which speeds up under load is undoubtedly a compound-wound motor which has been incorrectly connected for "differential compouding", and this is a design or installation error.

Or, and the 10EE does all this without any tachometer feedback, although there were some third-party dc drives which had tachometer feedback, and which required this feedback as these drives had no other way to detect loss of field, which will cause a dc motor to runaway and destroy itself.

Monarch used dc drives on its super-precision toolroom lathes, and used other means on its engine lathes.