View Full Version : electrical questions?

08-17-2009, 11:38 AM
Hi guys
Im wanting to move my lathe and mill into my garage at home. I know the mill wouldnt be any problem to hook up, but my old 1941 Sidney lathe is 5-hp 3-phase and is run on 600-volts. My question is, do I need to swap out the motor on the lathe to run it in a home shop? Or , could I run it on a rotary phase converter like I do on my mill? As far as I know the house has 100 amp service. What are my options here? I would rather not swap out the motor if I could avoid it. The lathe has a very large heavy motor, and Im looking for the easyest way to get it up and running without making a motor swap.

I have very little electrical smarts, so I would like to hear from those that managed to keep their machines original, without changing out the motor.

The other question I have for you guys is , how much wt can a home garage take? My lathe can be seen in pics on this site if you type in 1941 Sidney lathe. I dont really know what the proper wt is on this machine. Its a 14 inch swing, about 32 0n centres. The drive way, and garage is concrete. The wife is questionable about putting that much wt in there. Im thinking of putting the lathe& mill, with all the tooling, and a few tool boxes as well.
The concrete driveway has cracks in it, but the garage floor dosnt have any yet!
So, if this is a bad idea, please let me know.

THX Paul

08-17-2009, 12:00 PM
as regards the concrete... There's no way of knowing without drilling into it to findout the thickness and quality of the concrete and the underlying substrate and ground. In my own home I have concrete laid by the original owners 6" thick but the underlying ground is a mixture of clay and gravel that takes very heavy loading (it needs a jack hammer to dig a hole round here and you can park 30 ton trucks on the grass). But subsequent owners have laid areas that a just screed on soft earth. (a hole had been previously dug then filled!).

08-17-2009, 12:27 PM
I just moved in a 20" L & S lathe into my garage that weighs about 8,000 lbs. The concrete slab I doubt is over 3" thick. Yes, there are cracks in the slab.:( :eek: The ground under my slab is fairly stable with cleatcy lime stone rock not too far down.


08-17-2009, 01:18 PM

In the 3 phase rotary phase converter will work fine for your lathe. You will also need to check to see if you can change the taps on the motor for 240V or find a step up 3 phase dry transformer 240/600V to go between your phase converter and your motor. It will probably need to be a 7.5 kW


Steve Steven
08-17-2009, 02:30 PM
I just helped a friend make up a rotary converter with a three-phase transformer to run a 3hp 575 volt lathe motor, its working fine. The motor was Canadian, and labeled for 575 volts 3-phase. The rotary converter and transformer put out 600V 3-phase, it runs fine on that voltage.


08-17-2009, 03:51 PM
Hey guys
Sounds like a rotarty phase converter will work on the lathe too. My mill came with the rotary phase converter attached, so I know very little about them.
In my search for the new rotary phase converter, I would quess that the information I give the supplyer would be enough to get me set up? I know that the place has 100 amp service, so 220 single phase in , shouldnt be any problem. I need this to power a 600 three phase machine. might look around on the net to see if its possible for me to build one as others have.

Thx Paul

08-17-2009, 05:08 PM
I know that the place has 100 amp service, so 220 single phase in , shouldnt be any problem. I need this to power a 600 three phase machine.Huh??

A rotary converter will generate a usable 220V 3-phase from normal domestic single-phase 220V. It won't turn 220V into 600V.

08-17-2009, 07:44 PM
Ok, guys, now Im a bit confused about these rotary phase converters. I read the posts and thought it could be done, and reading the last post, it sounds like it can not be done. Could someone here set me straight on this. If I need to swap out the motor, I could but really dont want to go there. The motors pully will be one problem, then the mounting will cause even more troubles that I really would like to avoid. swaping out the motor isnt as easy as one would think, I debated doing that a while back to speed up the lathe a few hundred rpm, then decided against it due to all the bs PM member Beckly encounterd swaping a motor in his lathe,his set up very simular to mine.

whats the options guys?

thx Paul

J Tiers
08-17-2009, 09:25 PM
You will need 2 pieces.....

1) conversion to 3 phase....... VFD or rotary converter.

2) voltage step-up. Transformer.

It does not matter which way you do it, step up and then conversion, or conversion and then step-up.

Step-up first is expensive using a VFD, but could be cheaper with a rotary. But you need a bigger transformer (more $$$).

Conversion first and then step-up uses a bigger motor/converter, but a smaller transformer. probably the cheapest way, and lets you use other 240V 3 phase machines easily.

Don't be confused by Steve Stevens..... it sounds like the thing was in Canada., where 575VAC is not unknown.

08-17-2009, 09:25 PM
The rotary will change single phase 220 to 3 phase 220 by making the 3rd leg but you will have to add a transformer to boost 220 volts to 600 volts

08-18-2009, 12:37 AM
J Tiers and Lane are right, You will need both a voltage increase and 3 phase conversion. My approach to this would be to step up the voltage first then do the conversion with a VFD. I will assume that you need 575 volts 3 phase. I would start with a 10 KVA 230X575 volt single phase transformer and a 7.5 or 10 HP VFD (I will leave the de-rating up to you, I would use the 10HP VFD myself). The whole thing will require a 50 amp 230 volt feed circuit and the price for all of the parts and pieces WILL greatly exceed the cost of a 5 HP 230 volt single phase motor. Sorry to be a party pooper but thems the facts :rolleyes: . I would replace the motor.


PS: If you want the variable speed capability then I would look at the cost of the above option and also the cost of a 5 HP 230 volt 3 phase motor and a 10 HP 230 volt VFD.

08-18-2009, 03:01 AM
A SUV in a garage puts more psi in the 4 points where they sit on the ground then you will ever have on that lathe.

J Tiers
08-18-2009, 09:03 AM
A 575 V VFD is REALLY expensive.

A 220V rotary converter and a transformer will cost a lot less.

A 5 HP 220V motor would avoid the transformer, but probably won't be 'free" either.

I'd reckon your costs to be around $500 if you shop right, possibly less, possibly more.

08-18-2009, 11:17 AM
Just for arguments sake, a quick Google shows a 5 HP 220V 3450 RPM motor from Grizzly for $340. A 5 PH 3 phase 230/460V at Wholesale Tool is $395. You'll be out some money no matter what.

08-18-2009, 11:52 PM
did i miss what rpm you need from the motor ? i think i have a 5hp 1800 rpm motor im not using. new too. half of what grainger is selling it for. . .
interested ?

08-19-2009, 01:47 PM
did i miss what rpm you need from the motor ? i think i have a 5hp 1800 rpm motor im not using. new too. half of what grainger is selling it for. . .
interested ?

Thanks for the offer David
The motor on my lathe is a 1200 RPM job,,not easy to find those.
I just might have to change out the motor and use a vfd to slow things down abit. Im thinking to keep expenses down, the motor swap would be the cheap way now.
THX Paul