# 3phase/1phase which to prefer?

1. Sep 5, 2011

### kirancy

which one is preferred 3-phase or single phase?
in scott connection we convert 3 phase to phase is it possible to convert to single phase?
what is the need to convert to two phase?
what are the advantages of each of the 1,2,3 phase over the other?

2. Sep 5, 2011

### Averagesupernova

Sounds like homework.

3. Sep 6, 2011

### kirancy

why do you think so?

4. Sep 6, 2011

### Carl Pugh

Sounds like homework to me too.
Why are you asking these questions?
Single phase and three phase are both in common use. It depends on the application which is best.
The Scott transformer is usually used in converting 3 phase to 3 phase at different voltages. (My experience) The question is incorrect.
Two phase is only used for motors. Two phase is never converted from 3 phase. (Again my experience)
Advantages of 1 phase, 2 phase and 3 phase I will leave for you to find out. Most text books explain the advantages and you could also research it on the WWW.

5. Sep 6, 2011

### Averagesupernova

I think a scott-tee transformer configuration can switch between actual 2 phase and 3 phase. When I say 2 phase I mean ACTUAL 2 phase, not 240 volt split phase which is common in the USA.

6. Sep 8, 2011

### kirancy

if we talk about the output power the power in 3-phase is more than compared t single,but there wiill be more losses in 3 phase than single so is single better compared to three phase

7. Sep 8, 2011

### kirancy

in scott connection the three phase can definitely be converted into two phase but is it necessary to convert

8. Sep 8, 2011

### Carl Pugh

If you are using motors, three phase is better. (Three phase motors are better)
Three phase is also better if you are rectifying the voltage.(Less ripple)
If you have long transmission lines, three phase is better. (Lower cost for same power)
Three phase is also better if you have very high power. (Smaller conductors)

For the same KVA, single phase transformers are generally slightly cheaper.
Single phase wiring is slightly cheaper.
Single phase wiring is simplifier.

Scott connected transformers are rarely used.
If anyone knows examples of practical use of Scott connected transformers why don't you post it here.

Scott connected transformers are occasionally used by the power companies. The power companies want a tall thin transformer to mount on top of poles. They use a Scott connected transformer with one transformer on top of the other transformer. The transformers are connected for three phase in and out.

The preceding is the opinion of Carl Pugh and there are undoubtedly other Engineers here who have other opinions.

9. Sep 11, 2011

### aravind.vlb

what carl says is the best explanation

10. Sep 11, 2011

### Phrak

What kind of two phase is this? In the US it consisted of two phases 90 degrees apart. If your Scotish 2 phase isn't two phases 120 degrees apart, it's difficult to see how it can be convertede to 3 phase.

11. Sep 11, 2011

### Averagesupernova

Phrak, do a search here on this forum about the scott-t connection. I participated in a thread that had some explanations but I don't remember exactly the details. I recall some links being posted that were informative.

12. Sep 11, 2011

### b.shahvir

Scott connection is mostly used in electric traction for conversion of 3 phase into 1 phase. They are also used for industrial furnace applications.

13. Sep 16, 2011

### kirancy

thank you one and all