# Multi-Phase or more then three phase

1. Aug 27, 2009

### muet

Hi

i want know about two phase and three phase which is more using?.. In where
and what is use of more then three phase and in where
thanks

2. Aug 27, 2009

### famousken

Hi, three phase is by far the most common type of electrical transmission, there is no such thing as two phase, only single phase. more phases are possible and used in such things as stepper motors but I dont believe they are used for power transmission

3. Aug 27, 2009

### Phrak

That which is called 'split phase' consists of two phases 180 degrees apart. Why it is bad manners to refer to two phases 180 degrees apart as 'two phase', is beyond me. The original designation of two phase (two phases 90 degrees apart) disappeared from common use 70 years ago. I think it's time to let it go.

4. Aug 27, 2009

### famousken

Its not used in power transmission though, all power to homes and businesses (at least in the US-Im not sure how its done in other countries) is derived from 3 phase power. If you have 120/240 service for example; The pole transformer is connected to a single phase of the three phases of the service line, so a 240 circuit with two "legs" 180 degrees apart is therefore still single phase power. If you look at any 240v appliance it will say "240V, X A, single phase"

5. Aug 28, 2009

### muet

and about multiphase generator Can they produced more then 3-voltage or there waveform ?
if the have more then three coils?

6. Aug 28, 2009

### vk6kro

Sure it could be done. As you say, just have more coils.

But the extra complexity of control circuits, transformers and transmission towers would not be worth the effort. I can't think of any example of this being done.

The main point of using 3 phase is that you can have very efficient motors that start without starter coils etc. You get more power than with single phase, but you could get that with more wires or thicker wires.

7. Aug 29, 2009

### Phrak

Yes, I know what it's called. Refer to the definition of phase, or phasor for that matter.

8. Aug 29, 2009

### Averagesupernova

I would tend to lean towards not letting it go. It's not 2 phase, or split-phase or whatever before the transformer. So if you are going to call it 2 phase, then you could say that anything that has a power supply with a transformer with a center tapped secondary uses '2 phase'.
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Incidentally, I'm not sure the term 'split phase' is correct either. Single phase induction motors that have a high resistance starting winding are called split phase.

9. Aug 29, 2009

### Phrak

In fact, it would use two phases.