As AC generation goes from single phase to three phase the power increases three times. Then why generation station do not produce 6 phase or 12 phase electricity?
6 and 12 are multiples of 3. one of the advantage of 3 phase ac is that 3rd harmonic and its multiples cancels out. so going for 6 or12 phase will only lead to extra cost and maintenance in the transmission and distribution lines.
Refering to kishore"s I would like to say that the benefit mentioned by him is applicable to Six Phase also, since a Six Phase System can be considered as two mutually coupled Three Phase Systems and if analyzed using' a' operator instead of 'b' operator it is found that there is mutual coupling between Zero Sequence Components only and no mutual coupling between the Positive or Negative sequences of the constituent Three Phase Systems of the Six Phase System.
Refer to our Article(mentioned in R.G. also under my Contributions).
Dual three phase transformation for comprehensive fault analysis of a six phase system
P.S. Subramanyam a,, A. Chandrasekaran , S. Elangovan
Electric Power Systems Research 40 (1997) 85-90 :
We have worked a Lot on Six Phase Systems and Integrated Three Phase-Six Phase System.
Abroad there are some( a Few) Six Phase Systems Operating and under Test also.
P.S.
On the transmission side, if you use more than 3 phases (4,5,6 etc) you are going to need more conductors to get the power from generation to consumer, and unnecessarily complicate transmission. We have established networks with 3-phase transmission (we also do HVDC and convert back to 3-phase AC nowadays)
3-phase machines are really efficient (modern Generators in upper nineties %), so one will have to really have good reason to change an established efficient system. The three phase system is already pretty good with respect to efficiency, cost and complexity.
One aspect that can improve is to get the generator closer to the consumer, and eliminate (or at least minimize) conversion & transmission losses, e.g. distributed generation, local storage, local generation etc.
6 phase AC transmission cost alot. more power lines required, more losses...
6 or 12 phases can be produced if generator armature winding is designed accordingly.
Have a look at this on U Tube
https://www.youtube.com/watch?v=HqZtptHnC2I
David Johnson is right in saying that we need more conductors for Transmitting Six Phase Power.
There are two ways of transmitting six phase power.
# by going for Six Phase Compact Lines with distance between adjacent Phases being as little as 3' for 80 K.V. to Ground. Here we need to have a small Transmission corridor, which is useful where it is difficult to get a Right of way Space.
# by converting the existing three phase Double Circuit Line into a Six Phase Single Circuit Line, which does not require much of modification, or additional space, not involving much of cost, This alternative is the Best one and we can have the Benefits of Six Phase System in an Integrated Three Phase-Six Phase System., In such a case, all the existing Three Phase System and Equipments can be made use of.
Six Phase Transmission is more advantageous regarding Stability, Voltage Regulation, efficiency, Reliability etc. It is a challenger to H.V.D.C. Transmission giving more or less the same benefits at a competitive cost as we do not need High Power Converters/Inverters and associated control circuitry and control gear.
There is lot of Literature on Six Phase Systems.
As we go for more Phases like 12, 24 Phases etc the system approximates to H.V.D.C. Transmission. But their Feasibility and other aspects have not yet been studied in greater detail. Multi- phase transmission is a Fertile Area for Research.
To go for a complete Six Phase system from Generation to T & D and all six phase utility Devices, is a costly affair.
At present the Integrated Three Phase-Six Phase System. seems to be the Best Alternative and Competitor to combined 3-Phase and H,V,D,C, System on all counts including cost economics.
P.S.
Transmission could be done using any number of phases but three phase system has been established and working efficiently. Increasing the number of phases increases the system's complexity. It is really difficult to change a system adopted worldwide with out reasonable benefits.
with no of conductors increasing, losses increases.I prefer , if at all there is any need of 6 or 12 phase (for research/ experimentation), then it can be achieved at the load side rather than the transmission side.this way we can minimize the losses.Also the circuits for the 6/12 phase system will definitely be more complex compared to 3 phase systems.So, one must have a very good reason to switch to 6/12 phase ac transmission.
Resistance of conductor R=(Resistivity)(Length)/Area, To transmit same power by 6 or 12 phase, instead of 3, 6 or 12 lines will be needed with cross section area 1/6 or 1/12, compare to 1/3. Isqr.R loss would be double for 6, and fourtime for 12, with more installation and maintenance cost, without any benifit. For higher generating efficiency, the A.C machine needs,to work at higher flux density(produce flat top flux wave form), which generates 3rd harmonics, and its multiple in voltage wave form, which can be taken, care of by 3 or multiple of 3 phase generation then why not 3 with higher efficiency and reliability ?????????
This has to do with efficiency and cost trade off, thus the of implementing 4,5,6, or 12 phases maybe too high.
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