Turning two phase mains into three phase

[Paddy1000111]

15 minutes ago, Squaredy said:

You are correct there are always three phases.  Most streets have groups of houses on each of the three phases.  The problem is that only two phases reach my site.  The third phase stops about a mile away....

Going single phase to 3 phase is easy enough. Not sure about 2 phase to 3 phase though (tbh I didn't know a 2 phase site existed as I don't know why they would terminate the other phase at the consumer point). You can take single phase and use a phase converter to change it to 3 phase. It takes the single phase 100A supply and converts it to 3 phase although a 100A single phase would only give you ~56A (assuming a .8 power factor) of three phase plus conversion loss so you wont gain any wattage, just the ability to run 3 phase tooling. 

 

Not sure about adding a 3rd phase to the existing two. You would struggle having all three phases matched as the third one that you are effectively making will have a tendency to drift and then that screws with your power factors/heat etc etc 

[Squaredy]

6 minutes ago, Craig. said:

It can be done using a phase converter.

A static one would suit smaller machines, a rotary one would be better for a mill.

Yes it can be done with a phase converter, but it looks as if there might be an easier way.

[Squaredy]

6 minutes ago, roys said:

When you say only 2 phases are reaching your site, is this a remote site with a transformer on a pole. If so it is probably an 11kV 2 phase to 240V transformer, so at your service head ( the bit where the cable terminates in your property there will be just one service fuse and one meter, giving you only one usable phase.

Of course having not seen your place you maybe do have two phases and two meters.

Yeah there are definitely two phases coming in each with its own 80amp fuse.  And it has been confirmed to me by Western Power Distribution that there are two phases,  Why they didn't put in all three when it was wired up in the fifties I have no idea, but as I drive around rural areas I do notice that two wires on poles is quite common, which would be two phases so I think it is not unusual.

[Paddy1000111]

41 minutes ago, Squaredy said:

Yeah there are definitely two phases coming in each with its own 80amp fuse.  And it has been confirmed to me by Western Power Distribution that there are two phases,  Why they didn't put in all three when it was wired up in the fifties I have no idea, but as I drive around rural areas I do notice that two wires on poles is quite common, which would be two phases so I think it is not unusual.

Out of interest what wattage is the three phase kit you want to set up? 

[Squaredy]

3 minutes ago, Paddy1000111 said:

Out of interest what wattage is the three phase kit you want to set up? 

New mill would be 13KW.

[Paddy1000111]

4 minutes ago, Squaredy said:

New mill would be 13KW.

You're not asking a tonne but that's 13kw@415v? If so that's about 21A 3ph. 13kw@230v is 38A 3ph which means it would be about 66A@240v single phase? 

 

You could get away with it on a rotary single phase converter but the 80A rotary converters can only handle single motors up to 11kw. You would need a 100A supply to give you a 15kw single motor rating. Maybe that's something that your power company can do a bit easier? 

 

I don't think you're going to have much luck with changing two phase to 3 phase. You would have to use both the phases coming in to create your third phase and then you will have issues with phase correction and making sure you have clean power or it's going to start messing up your load factors. If you unevenly load one phase you can also have the current lost down the neutral line which is another headache. Converting the 230v to 415 is easy enough with transformers but it's then taking those and creating a 3rd balanced phase with them that you will struggle with 

[Watercourse management]

Most farms had a two phase supply in the old days,a lot of the old feed mills were two phase. Unfortunately ours is only single phase,looked into a rotary phase converter good bit of kit to run multiple motors in phase but the price of electricity now I need to see if diesel is cheaper when running big motors.

[openspaceman]

1 hour ago, Squaredy said:

Yeah there are definitely two phases coming in each with its own 80amp fuse. 

So you have 380-440V between then and 230-250V between each and earth?

 

Theoretically you could stick a bigger 3ph motor wiring 2 of it's terminals with the incoming  phases and each coil to earth and then once that is spinning draw 3ph of each terminal as the rotating squirrel cage will induce the third phase.

 

Mind it is 50 years since I studied electrical engineering.

[Squaredy]

4 minutes ago, Paddy1000111 said:

You're not asking a tonne but that's 13kw@415v? If so that's about 21A 3ph. 13kw@230v is 38A 3ph which means it would be about 66A@240v single phase? 

 

You could get away with it on a rotary single phase converter but the 80A rotary converters can only handle single motors up to 11kw. You would need a 100A supply to give you a 15kw single motor rating. Maybe that's something that your power company can do a bit easier? 

 

I don't think you're going to have much luck with changing two phase to 3 phase. You would have to use both the phases coming in to create your third phase and then you will have issues with phase correction and making sure you have clean power or it's going to start messing up your load factors. If you unevenly load one phase you can also have the current lost down the neutral line which is another headache. Converting the 230v to 415 is easy enough with transformers but it's then taking those and creating a 3rd balanced phase with them that you will struggle with 

Yes 13kw @ 415 volts.

 

My helpful professor is indeed suggesting using transformers to create the third phase.  I appreciate your concerns, which is partly why I asked the question.  I would rather raise potential problems before committing myself, and pass on these concerns to my guru.

[gobbypunk]

Hi mate I looked into 3 phase options for ages talked to people who make the phase converters and I think at 13k you would need a rotory converter and it would be expensive I can give you Pete at Transwave Converters if you want he is a font of knowledge and would probably have a good idea