Phase converter

[mriplaybass]

A few months ago, I purchased a Hamilton lathe. It's a monster, and way more than what I actually need, but the price was too good to pass up. I have not operated a lathe in 45 years, so I am about as green of a novice as they come. Right now, the lathe is still in my trailer, because it took 4 of us to get it in, and now with Covid19, and social distancing, there's no one to help me get it into my shop. So while I wait, I thought I would figure out what I need to do to power it up once it is in my shop. It has a 3hp 3phase motor. What is the best way to power it up? I don't have 3phase power, so I am left with some sort of converter. I understand that with a static converter, I will only get 2/3 of the motors output. Probably not a problem for the time being since I will only be doing small projects to cut my teeth on. I would love to get a rotary converter, but being retired, cost is a consideration. Any input/recommendations would be appreciated.
Also, I am curious. I have seen lathes that have some sort of brake on them that causes them to stop rotating almost immediately when the power is turned off like a lawn mower does. Is this a function of running true 3 phase vs a static converter which only powers the motor in single phase? or is there some sort of mechanical brake that does this? Would a lathe as old as mine even have a brake on it?
Thanks for any help in advance!

 

[matthewsx]

Hello and welcome, I play bass too

There are basically 4 ways to deal with your situation.

1. Static phase converter - changes 240v single phase into 3 phase. Downside is you loose some power.

2. Rotary phase converter - same as above without power loss. Both phase converters have the advantage of not having to modify the machine beyond just hooking it up.

3. VFD (variable phase converter) can provide variable speed and braking along with other features but may be challenging to wire into existing controls.

4. Change the motor to a single phase unit.

What will work best for you is a matter of how good you are with electrical, how much effort you want to put into it, and how complex your machine is.

Post up some pictures along with your specific model number and folks will be able to give better advice.

John

 

[cathead]

If your Hamilton is large and budget is small, an RPC made with a used 3 phase motor would
be my choice. There are many good discarded 3 phase motors available inexpensively in
scrap yards. Other than that all one needs is a couple capacitors, a relay and two switches,
and some wire. I have constructed a few of them and have never spent over $100 to build one up.

 

[tjb]

I have a rotary phase converter that I bought new and have been very satisfied with it. A little pricey, but the advantage is it's fairly straightforward to install and use. If you decide to investigate RPC's, size/capacity is important. I was told that the horsepower you should purchase is determined by taking the highest horsepower motor the RPC will run and doubling it. I did that and rounded up to 10 HP. Glad I did because I have since purchased a machine that is 5HP.

Regards

 

[projectnut]

I would agree with mathersx. One caveat on changing the motor however. Depending on the size and rpm of the motor currently on the machine a single phase motor may be hard to find, require a dedicated circuit, or even draw too many amps to be practical.

I would check the motor nameplate before making a decision. If the motor is in the 7 to 10 hp range a single phase motor is likely to cost more than the machine itself. Keep in mind you'll also have to replace the current motor with one using a similar mounting platform.

My personal preference for anything in the 5 to 10 hp range would be either a static or rotary converter. A good VFD to run a motor that size can be pricey, and as mentioned will require rewiring the controls.

I have several 3 phase machines in the shop including a milling machine, lathe, power hacksaw and drill grinder. At this point in time they all run off static converters. I do have all the components for a 15 hp rotary converter to power the entire lot, but have yet to install it. I even had another sub panel added to power it. Somewhere along the line I lost interest in completing the job. All the machines run fine on the current static converters and none lack for power. The mill has been on the static converter going on 20 years. Sometimes it works 60 hours a week and never gives problems. The lathe and power hacksaw have been running on the static converters for about 5 years. Again neither lack power or overheat. The lathe is run up to 40 hours a week while the saw has only had minimal use.

 

[mriplaybass]

Thanks for the replies! A little more information on my lathe. As I said, it is a Hamilton. I would not be surprised to find out that it is 75 to 100 years old from the little bit of information that I have been able to find on it. I did find some information on the next biggest model, and discovered that the 16" swing unit weighs around 3,300lbs, so taking a guess, I would say that this one is around 3,000lbs I have not measured anything on it yet since it is still sitting inside my trailer covered up waiting for me to figure out how to get it out of there. The information that I got from the previous owner is that it is 36" between centers, and 14" swing. I'll figure that out once I get it into my shop.
I have looked on Facebook market place and found a few used rotary converters in the $200 to $300 range. I have found 3phase motors (5hp) for around $100. On eBay, I am finding the control panels in the $135 to $175 range. The lathe is powered by a 3hp gearhead motor.
I have really not had much time to try to figure anything out as far as what control does what. What little information I have, I got on the Lathes.co.uk site. But, until I am able to power the lathe up, I can't do much to learn how to operate it. Turning the chuck by hand gets pretty tiresome!
The previous owner powered the lathe with a static converter that looked to be about the size of a double electrical outlet box, and said that he had no problems with it. Most of the items that I hope to make, are going to be relatively small such as bushings, friction bearings, threaded rods etc. The main reason I purchased such a large lathe is that I will be doing things like retubing axles on off road vehicles, and need to turn the correct diameters to press the tubes into the differential housing, and fit the seals in properly. At least that is the plan right now.

 

[matthewsx]

Looks like a nice lathe, it's hard to tell from your pictures but it looks like the spindle motor is the only thing that takes power. If that's the case I would definitely go with a VFD for ease of setting speeds, I have one for my Star lathe and it's really nice for getting cutting speed just right.

A "good" one in the 3hp range is $200 - $300 and an ebay cheapie is just over $100. Either will power your machine and if you only have an on/off/reverse switch the wiring should be simple. Just remember, no switches between the VFD and the motor, if you want to use the original switch it will need to be wired to the VFD control circuit.

John

 

[mriplaybass]

Thanks John
I don't know what switches are on the lathe, but I'm pretty sure it is just on, off, reverse. Kind of sounds like VFD is the way for me to go until I actually learn how to operate it.

 

[JimDawson]

I think I like the static phase converter option for that motor. It is an antique and sometime the insulation is not up to the task for the spikey VFD output.

 

[matthewsx]

If that was working for the previous owner then why not? Does he still have it?

John