About 3 Phase Power Supply

[shermaine]

Can we actually convert a three phase power supply to one phase?
Please advise. Thanks.

 

[Nigel Goodwin]

Can we actually convert a three phase power supply to one phase?
Please advise. Thanks.

Just use neutral and one of the phases, it's how most domestic wiring is done.

If this isn't what you want, perhaps you could be more specific?.

 

[Damocles]

Depends what you want to do. Putting all the load just between one phase and neutral is not a good idea. Electrical distribution network does it by connecting one house in turn to each phase so the result roughly evens out. If you have a three phase generator and only connected between neutral and one phase then it would get very upset. If each phase is drawing the same current then the generator always has exactly the same load as it turns, which is what makes machinery happy.

 

[Fawad]

How 2 get a 400 v using 3 phase supply 4rm two 230 v live wire with phase diff of 120 degree phase diff

 

[mbarazeen]

if your question is about having a balanced consumption from a 3phase supply and get a single phase out, the answer is yes, but not by using transformers.
you should have a rectifier and inverter to do this.

fawad,

type in good way and post your question.
by the way when you measure between two 230V wires at 120 shift, you will get a value of 400V.

so just have to connect phase to phase and you have a single phase 400V

 

[tcmtech]

Very few single phase loads are large enough to ever justify having to use a three phase source to drive them.
Also any decent quality three phase generator regardless of size will handle at least 50% of it capacity being drawn off of any one phase. Most will take far higher than that.

There is a sort of odd connection set up commonly referred to as a 'Z' connection that allows for an odd three phase to single phase conversion that will carry a fairly even load split on the three phase source but gives a true single phase output.

I have a old military three phase gen set that is rated for up to 80% load on any single phase output when set up as a three phase source but when configured to the 'Z' connection it will easily take being ran continuously at its 120% capacity level as a single phase supply.

 

[mbarazeen]

i really missed the point of Z connection, thanks tcmtech,

its like using all three phase windings in such a way to sum and get a single phase. for this, a three phase transformer is required to be modified to have its 3rd phase(any phase) connection reversed and seriesed with other two. it will work as a single phase.

if the phase to phase out put voltage of the transformer is Vp
then the out put of the modified transformer would be,

Vout= 2Vp

so using a special transformer converting a three phase supply to a single phase is possible. but the frequesncy would be the same.
its the same in case of generators too.

 

[tcmtech]

Yes with the Z connection you still have the same base frequency.
As far as the output voltage what you will get is it will make a 120/208 three phase supply source into a 120/240 single phase supply source or a 120 only supply source.
The original center point and one phase line (L1) output still have the same line and common connections (N) but as you said one other phase gets reversed(phase 2) . Then it gets added on top of the third phase output (L3) but now its mostly out of phase with it so the total line to line voltage(L2N - L3) is the same as the single first phase voltage (L1 - N).
At that point it can be used either in series or parallel with the L1 - N winding depending upon what voltage you need.

Its sort of weird how it works but its does in fact work!

 

[MrAl]

Hello,


You can also use a three phase motor generator where the generator has a single phase output.

 

[mbarazeen]

yes sure its possible by coupling a 3 phase motor and a generator of single phase. but here i understoor he needs a static equipment.

 

[tcmtech]

The motor generator system would work but the efficiency is far lower, the unit is much bigger, and the cost for one is far higher.