Dual speed 3 phase motor from single phase supply

[robertlaurenson]

Hello everyone I have just bought a new lathe, (used) its on its way to me from other end of the country now. I have only just realised i may have an issue. The machine is 3 phase and i was intending to go down the VFD route but because its a dual speed motor im not sure i can. See attached image of motor name plate. It also says its 380 rather than 400v, its an old machine so maybe thats normal? My workshop supply is split phase, 2x100a incomers on a 3 phase cutout, no 3 phase available near me. I have the offer of a little used transwave 5.5kw static converter, but im not sure if itll work either. Any help is much appreciated Thanks Robert
 

 

[Rob.]

What you want to do is possible. 

Unless you got this new lathe at an extremely low low price, you'd have saved a ton of money getting something suitable. 

 

[robertlaurenson]

Rob,

Because of the size lathe i need (quite large one) getting a single phase one was out of the question, and this one was really  cheap to be honest, the guy just needed clear of it. so i have saved around 1500 pounds compared to anything comparable. 

I have asked this on other forums and there is another option the folk on there have mentioned that i dont quite understand.

They say to take the two legs of the split phase supply into a transformer, which will create the 3rd, is this something which is doable?

thanks

Robert

 

[roys]

What size of motor is it, 3HP ?

 

[Rob.]

Rob,

Because of the size lathe i need (quite large one) getting a single phase one was out of the question, and this one was really  cheap to be honest, the guy just needed clear of it. so i have saved around 1500 pounds compared to anything comparable. 

I have asked this on other forums and there is another option the folk on there have mentioned that i dont quite understand.

They say to take the two legs of the split phase supply into a transformer, which will create the 3rd, is this something which is doable?

thanks

Robert

No, you can't put 2 legs of a split phase system an create 3 phase with only a transformer. 

Strip the motor out, find one that will run on 230V three phase and still meets your other requirements, size, rrpm etc.. 

Then buy an inverter to run it. 

All of this I presume is for personal home use? This lathe isn't going to be used for business purposes right? If it is, sell it. 

 

[robertlaurenson]

No, you can't put 2 legs of a split phase system an create 3 phase with only a transformer. 

Strip the motor out, find one that will run on 230V three phase and still meets your other requirements, size, rrpm etc.. 

Then buy an inverter to run it. 

All of this I presume is for personal home use? This lathe isn't going to be used for business purposes right? If it is, sell it. 

It is for personal use at first but my plan is to set up a business which this will be the workshop, 

So i guess you could say it is for business use, 

This for sure wont by my only 3 phase machine and rather than sell it i think where i need to look is forward and how to get a converted 3 phase supply from what i have.

I will most likely in the future have a press brake, guillotine, mill, and possibly many other things, so a converter of some sort will be required, a VFD isnt going to be an option for the bigger machines so i need to look at full workshop options going forward.

As far as i can see the 3 realistic options for a full workshop are 

1, Rotary Converter (either buy or build)

2, Drives Direct digital converter

3, Unique 3 Phase transformer option - just found this and reading up on it and considering buying the book to make it but not sure if it will work, any suggestions welcome.

As mentioned above, if any of you have any idea or opinion which is the right way for me to go then please let me know. 

Drives direct are probably the one i would choose if it werent for the high cost

And to be honest if it works, looking at the Unique 3 phase option seems like it could be the cheapest to make and the cheapest to run overall so not sure what to do

Thanks

Robert

 

[Geoff1946]

Getting a real 3phase supply would be best. What do you actually have? 

You call it split phase, then seem to infer that its two phases of a three phase system. It may be my sheltered upbringing but I've never see that.

I see you are in Shetland so perhaps it's something not usual on mainland UK (?).   Are your two phases 120 degrees apart or 180, as I believe is a common USA system?

 

[Andy™]

Getting a real 3phase supply would be best. What do you actually have? 

You call it split phase, then seem to infer that its two phases of a three phase system. It may be my sheltered upbringing but I've never see that.

I see you are in Shetland so perhaps it's something not usual on mainland UK (?).   Are your two phases 120 degrees apart or 180, as I believe is a common USA system?

worked on a few split phase 180 degres apart (230/460) but not any with 2 phases of a TP supply 120 degrees apart

 

[Tony S]

You’ll not get split phase from a 3Ph MV supply, there would be no point.

 

[robertlaurenson]

Hi all 
What i have is a "split phase" supply, there are only 2 overhead lines and i have a split phase supply from a center tapped transformer. 
The supply is 240v from phase to Neutral and 480v phase to phase, very similar to the USA 115, 230v system. 

The cost of installing 3 phase would be in the region of 25k, so certainly not something i intend to do at the moment, maybe in the future if the business takes off then yes but not just now.

So ultimately what are my options, the ones i know of so far are.

1, Rotary phase converter (either 240v or 480v input)

2, Static phase converter

3, VFD on each motor of each machine (i have just heard today that some VFD's can take a 480v input, which i think means that i can feed my 480 into it and then it becomes a plug and play into any given machine?)

4, The Unique3phase method? not sure on this one but it has been reccomended

Any help would be greatly appreciated.

Thanks

Robert

 

[BorisJ]

380v 3 phase is the mainland European voltage before they increased it to 230/400v.

Could you not change the motor for a single phase one? 

 

[Marvo]

I don't see anywhere what size motor you're dealing with.

3x Victron inverters paralleled will give you a 400v + neutral 3-phase output from a single phase input. I'm not sure if the 3 inverters need to be on the same phase or whether you could put them across 2 different phases, you'd need to do some homework. This would be more efficient than most static converters and would probably be more tolerant of high inrush and start currents. The price might be somewhat prohibitive however....

Most 380v motors will run happily on 400v, especially with older motors the voltage rating is nominal.