# Powering a 208 3  phase lathe from single phase



## Nutfarmer (Apr 23, 2020)

Trying to figure out how to power a Hardage lathe. There are three 3 phase motors and one dc motor, so vfd  is out. If I use a rotary phase converter the voltage will be 220 and the lathe is 208 volts. Can 220 volts be used or will I have to use a transformer? The main drive motor says suitable for 208 volt usage and the coolant motor says 208/220 volts. All the three phase motors i have worked with have been 220 or 440. The machine came  from a large shop with four cnc  machines. Haven't heard of cnc  running on 208. Will it run on three phase 220 or will that burn up the main drive motor and controls ?


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## Janderso (Apr 23, 2020)

I'm surprised you haven't received any response. I'm an idiot but here goes.
That 208 motor will be fine with 220. It's relating to 208 at 50 hz., kind of a European thing.
Now, I could be way wrong but that's what my gut is telling me.
Someone will be along to prove i'm an idiot


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## mksj (Apr 23, 2020)

Most motors are rated for a voltage variance, somewhere along the lines of +/-10% in the US, ideally +/- 5%. Contactor coils and such are typically specified as +/- 5%. All controls need be at the rated 60 Hz.  So you should be OK, but you need to make sure the transformer inputs use the line and not the wild leg.  You could also check the transformer input taps is there is any adjustment, but I doubt that a difference will be a problem. If your single phase line voltage was higher as often seen these days then you may want to consider a buck transformer.


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## JimDawson (Apr 23, 2020)

The easiest way it to use a rotary phase converter.  It is also possible to use a VFD on the spindle motor only, will require a bit of rewiring, and setting the voltage output to 208.  If the motor is 208 only, then it would be fine at 220V, but in North America our line voltage is 240V and that's kind of pushing it.

208 volt is pretty common in commercial/institutional facilities because it allows you to pull 120V single phase from any leg to neutral.  Not common in heavy industrial.  There are a lot of CNC machines that run on 208V, my Haas for instance, it's rated at 208V 3 phase, or 240V single phase, but I think it also runs just fine on 240V 3 phase, just have to set a jumper on the power supply.


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## Nutfarmer (Apr 23, 2020)

Mksj  thanks for the response. I think you verified my original thought that 220 Volts would be in the range of tolerance.
JimDawson information much appreciated. I will check line voltage . If just a single motor would use afd.
Janderso I miss the local meetings due to the virus thing. When you build your coolant tank for the grinder ,I can donate some magnets from a kubota  hyd. filter. They are about three inch rings and 1/8 inch thick.


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## projectnut (Apr 24, 2020)

As mentioned I don't think you'll have any problems running the 208 volt motor on 220 volts.  As a point of reference I have nearly 2 dozen machines in my shop with manufacture dates prior to 1984 when the standard was changed.  Mine have motors dating from the early 1940, some in the 1950's some in the 60's, some from the 70's and even a couple from the 1980's  They all have a 100% - 120% service factor  motors and some run for hours at a time.  They all seem to run fine on the current 220 volt rating.  None lack power or overheat.

They are all rated to run at the posted voltage + or - 10%.  The current standard for line voltage is 220 + or - 5%. So unless the line voltage exceeds the standard plus 5% for extended periods I don't think you'll have a problem.  You might want to check, but most industrial or commercial motors have overload protection.  Some are automatic, while others use a manual reset button.  In all cases that I am aware of the overload will shut down the motor long before any damage will occur from under or over voltage.


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## Bi11Hudson (Apr 24, 2020)

The 208 Volts quite likely comes from an old standard in the U.S. where transformation was done with a "Wye" connected transformer providing 208 / 117 Volts. The transformer was(is) center tapped to provide 208 phase to phase with 117 from phase to center tap, usually grounded. It is still used, though fairly rare now. 

When I worked at the "Pipe Shop"(a foundry) in the '70s, it was not that common for 240 circuits, but had a strong showing with 416 / 277. Last I checked, a while back, 277 lighting was still widely available.

The motor with a 208 Volt rating is probably an older model, designed before delta-delta became the norm for distribution. With the normal swing of voltages, +- 10%, there probably won't be any  problems. If you have a full *240* Volt line, it might be preferable to watch for motor overheating for a while. But for hobby use rather than production, you shouldn't notice any serious overheating.

The biggest concern with that rating is the implied age of the machine. I would watch insulation condition. That is a very old motor and the insulation may not be in that good a shape. Don't go into the motor unless you really need to. If you can get your hands on a megger, it would be a good idea to check it. But if not, don't worry about it. Just watch for trouble the first few times you fire it up.

There are many other comments on such a rating. I'm sure some will show up here over time. The bottom line though is that synthesized three phase is not a true sine wave, and older motors have some trouble with it. Especially if you get away from 60 Hz. If you do opt for a VFD, tune the output to a very low voltage, say 210-215. You should be able to go from 45 to 75 Hz with no problem beyond a reduction in power availability from the motor(s).

You speak of a DC motor as well. If the controller for the DC motor is onboard the machine, DC can be provided with a couple of bridge rectifiers. Set them up in "open delta" configuration and be prepared for a hell of an increase in the single phase input. Over and above the 1.73 multiplier. 

The DC won't be upset by the synthesized / stair-step waveform, regardless of output frequency. It simply is a matter of getting DC from the AC. The only concern there is to be sure to include that into the Horsepower rating of the VFD.

.


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## projectnut (Apr 24, 2020)

Bi11Hudson said:


> The 208 Volts quite likely comes from an old standard in the U.S. where transformation was done with a "Wye" connected transformer providing 208 / 117 Volts. The transformer was(is) center tapped to provide 208 phase to phase with 117 from phase to center tap, usually grounded. It is still used, though fairly rare now.
> 
> When I worked at the "Pipe Shop"(a foundry) in the '70s, it was not that common for 240 circuits, but had a strong showing with 416 / 277. Last I checked, a while back, 277 lighting was still widely available.
> 
> ...


The company I worked for used 277 volt lighting in almost all applications from offices, to production rooms, to shops and warehouses.  At one point in time we were having an awful time keeping lighting fixtures in stock.  They seemed to disappear from inventories on a regular basis.  Since there were no work orders or other paper work indicating when and where they had been installed there was a serious suspicion that there was "inventory shrinkage" otherwise known as theft or shop lifting.

We had a major push to replace all lighting where possible with 277 volt units.  In most cases it involved just changing out transformers and bulbs, but in some instances entire new fixtures had to be installed.  Keep in mind this is an industrial complex with several thousand lighting fixtures. 

Once the project was finished the inventory of lighting fixtures, bulbs, and ballasts stabilized.  Apparently there was no market for, or personal interest in 277 volt fixtures, transformers or bulbs.  Either that, or it would have been much easier to track the highly unusual items. They no longer disappeared without paperwork.  Although they never caught the culprits there were some suspects.  I don't think there was much doubt as to what happened, but trying to prove it after the fact would have been difficult at best.  When the suspected culprits either left for greener pastures or retired the "inventory shrinkage" diminished by a factor of 10.


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## Bi11Hudson (Apr 24, 2020)

For what it's worth, 277 volt lighting was/is a fairly common system.  It comes from transformation from a high voltage such as 2300, 4160 or 13.8KV down to 480 in a wye configuration. Phase voltage, 480, to neutral (center tap) of a wye is [phase/1.73=lighting]. Basically the same as 208/117. 

Such a configuration allows motor loads to run on 480 and lighting loads at 277 using one set of transformers and distribution lines. If there are few 120 convienence lines and mostly lighting, such as found in an industrial setup, it is the most effective arrangement. What few 240 or 120 loads are around use a local 480 to 240(120/120) single phase transformer.

.


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## ddickey (Apr 24, 2020)

It's actually 208/120.


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## Nutfarmer (Apr 24, 2020)

Closer inspection of the main drive motor shows it to be a two speed motor. That kind of mandates a rotary phase converter. Have no idea how to use a vfd  on that. Thanks for the help everyone . It is much appreciated.


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