on my "new" sb lathe the motor tag says 3-phase----BUT there is only 3 wires.---3-phase gotta have 4 wires----right? so my question is, could someone have had this motor rebuilt to run on single phase? ----its 220-v and the way the new wires to the switch shows I am thinking it had to be redone! There has never been 4 wires in the tube to the switch---only 3 -- all new black wires. Looks like from switch to motor there is only 2 old cloth covered wires.

Any ideas as to what I have here? --- I am kinda at a loss!

you have an old u-frame three-phase delta motor, ground lead is not brought out in the electrical box,just ground the frame..the three wires you have are ph1,ph2,ph3, 220v between any two wires. you can get cheap static converters for this motor.they go for about 150 bux. for $50 more you can put a VFD on it.

Will the VFD work on this old motor? watched a couple vids of guys putting them on new motors. ---- none on dinosaurs! lol!
What about the capacitor way of running 3ph on single? saw quite a few doing that. ---I am kinda in the dark when it comes to this stuff!

you can put a VFD on the motor you have Sonny,but I would test the motor out first if you can..take some basic resistance tests from the motor frame to the phase leads,look for shorts and phase to phase shorts as well..older motors have varnish insulation that doesnt last as long as the newer epoxy insulation. A VFD can also stress the insulation on older motors..The capacitor method of running a 3ph motor on single phase 240v will work at reduced horsepower output..usually 20mfd per HP run and 100mfd per HP start caps. The start caps switch in just for the motor start then the run caps run the 3rd phase. The static converters use this method, they are pretty cheap.

I have a static converter for 5 or 7 hp I think ---had it on our die press at the other place til we got the 3-ph. hook-up. Might also be one on my big shaper ---- its 3-ph. and 5 (I think hp) and 220-v. somebody at the school put it on since they only had single ph. in the building.
I see the 2 different 3-ph. systems, ---- 1 is 4 wire and the delta is 3 wire.
The seller said the place he bought the sb from turned it on and ran it to show that it did work, so I only have his word, but he seamed like a great guy so I will assume it is a good motor.
Its only 1 horse but looks like an elephant sitting on top of the lathe.

Sonny, 3phase power standards in the USA are set up three different ways..Delta uses 3 wires,usually only used for balanced loads-motors,refrigeration compressors and heat loads. Wye uses 4wires,it's the same as a delta system except it has a neutral wire(white on 208v,grey on 277v)that brings unbalanced currents back to the transformer(s) neutral,for 120v loads on a wye system.(or 277v on a 480v system) Wild leg 3phase uses two transformers,not used much anymore but you will find it in the cities still around in old buildings and sometimes on farms.Basic voltage systems here in the USA are 120/240 single phase,120/208v 3ph wye,4wire, 240v 3ph delta 3wire, and 277v/480v delta or wye.(Canada uses some 347v and 575v just to confuse you) Motors have gone thru some improvements over the years,efficiencies have gotten better,early motors were just numbered as to frame size,like 203 or 205 frame..then in '52 they rerated the frame sizes with a 'U' designation,and then again in 1964 they came out with the 'T'series frames(smaller,more compact designs) where it's been at since. Frame sizes are basically interchangeable from manufacturers across different brands,like a Lincoln 215T frame motor will interchange with a Baldor 215T frame,the only difference is the electrical box on the side,mounting dimensions,shaft sizes and centers are the same. Insulation has gotten better with newer epoxies and resins to coat the windings with..Inverters and VFD's create stresses on winding wires and cause pinholes in the insulation over time..manufacturers have come out with newer insulation that protects better and isnt affected by the VFDs.

Sonny take the static converter you have and wire a spare 5hp motor to it, then wire all your machines to that motor with a junction box or disconnect switch..then you'll have a crude 3ph system you can use

https://youtu.be/D1AatcuG3qU

Interesting video.
Gotta get to the farm and see what I can scarf off of the shaper! --I think its a 5 horse motor. The old sb is a 1 horse so maybe we have a start! lol!

Decent video... I have a 7.5 HP 3ph motor to use as a idler. I've got half a dozen 2 hp motors out of ice cream machines.. Like to put one on my lathe when I redo the drive. Hopefully with the rotary inverter I wont have any issues with reverse. I haven't had luck with the static inverters. I have a few of those I use just to test machines for function. no real load. Got plenty of 208/230 single phase up to 1hp to use as a pony/starter. No need for a neutral that way.

the VFD's are a VERY efficient way to power small motors, no sense anymore to use a phase converter with all that power wasting caps and rotor motor online just to run another..over 5hp then you might have to use a rotary but for under 5hp the VFD is the way to go. I recommend the Hitachi VFD's..I've used a lot on customer equipment that run them daily and never had a failure..the China made VFD's are coming along with the quality, pretty impressive for the price..with good applications assistance in our English language via email if you need it. Impressive. FWIW

I saw that they dont think vfs's on old motors is a good idea due to the insulation of the old motors . I have no idea about any of this, so I am kinda having to learn a bunch of stuff as to making something reasonable that will work.
Since I am only dealing with and old motor of 1 hp. it shouldnt take much. Also it will not be doing production runs,----just my use now and then.

Sonny, a simple cam or drum switch for Off/On + Forw/Reverse sometimes is the best bet..they last forever. I do VFD work for my electrical customers, but my old P+W lathe has a cam switch on it...go figure

This has a heavy drum switch on it ---- came factory equipped, so good on that end. The lathe just needs power to the motor and its ready to cut metal.

Sonny one of my air compressor motors has the special VFD wire inside it..it's a mid-90's vintage 5HP Baldor..just went past it this AM and thought of what we had been talking about


Ive wired plenty of motors without this internal wire, but if I had my choice in spec-ing out a motor for a VFD I'd choose it..air compressors with start/stop duty don't need it.