Can someone do my electrical maths please?

[ostell]

W = V x I
Power is proportional to current AND Voltage ( or I squared).

 

[prv]

4??
Three phase uses only three wires.

Is it not three phases plus neutral?

Pete

 

[ostell]

Is it not three phases plus neutral?

Pete

Depends if it is configured star or delta

 

[claudio]

Depends if it is configured star or delta

3 phase = 3 wires
3 phase plus neutral = 4 wires

Star or delta makes no difference

 

[VicS]

3 phase = 3 wires
3 phase plus neutral = 4 wires

Star or delta makes no difference

The centre point will be the neutral if it's "star". Where's the neutral if its "delta"

 

[claudio]

The centre point will be the neutral if it's "star". Where's the neutral if its "delta"

Delta wiring doesn't have a neutral. 3 phase machines don't require neutral, even in star mode.

Neutral is only used in single phase systems, to provide a lower voltage to domestic systems, i.e. in Europe 230V.


Edit: see http://en.wikipedia.org/wiki/Three-phase_electric_power

 

[John100156]

We digress but to help to explain: 3 Phase does not need a neutral if it serves a balanced load such as is the case for a motor, where the internal windings load each phase the same. Or even three identicle heating elements.

If there is an unbalanced load, such as a three phase system feeding three single phase circuits as in a commercial power supply in a building, then some form of a return path is necessary via a 4th route, a neutral/terra (earth) path.

For a balanced load this is because when one phase is high +VE the other two phases are -VE for instance considering one point on the sinusoidal wave form when one phase rises to say +240v the other two phases are -120v hence its in balance.

A step-down transformer will have three balanced windings on the primary side which will receive power from the 3 overhead cables as Vics has shown. It's when it serves an unbalanced load across the 3 phases a 4th cable is required.

 

[ostell]

See here for an explantion

 

[claudio]

A step-down transformer will have three balanced windings on the primary side which will receive power from the 3 overhead cables as Vics has shown. It's when it serves an unbalanced load across the 3 phases a 4th cable is required.

Not always the case, often when a neutral is not available a transformer connected to two phases is used to supply the unbalanced load

 

[cimo]

I am just trying to figure out how much power I am losing by not upgrading the cable.

I figure that even with very large cables I am going to lose say 5%. If I am only losing 10% with my current cable, then I am not that fussed. However if it is up to 20% then it needs to be added to the list of jobs to do.

for a 12v system with your cable run, air breeze recommend 16mm^2 cable. Cable power losses aside, smaller cables will also reduce the voltage at which the W/G begins to regulate - i.e. prematurely stops charging your batt. bank. Your W/G outputs DC, so 3-phase considerations not relevant.

 

[claudio]

Not all wind generators generate 12VDC.

Many are rectified DC, open circuit voltage can rise to around 60V or more, the output is connected to an external regulator, some ARE 3 phase which are rectified remotely and then connect to a regulator.

The Airbreeze requires 16mm cable because it is regulated to 12V. Bad idea, bad design. Cable size and length is critical because they don't even have remote voltage sensing

Edit: Just re-read the thread, OP does have Air Breeze, so its 16mm cable minimum

 

[VicS]

for a 12v system with your cable run, air breeze recommend 16mm^2 cable. Cable power losses aside, smaller cables will also reduce the voltage at which the W/G begins to regulate - i.e. prematurely stops charging your batt. bank. Your W/G outputs DC, so 3-phase considerations not relevant.

And that compares closely enough with my suggestion, in post #4, that 15mm² cable would be about right.

 

[nigelmercier]

And that compares closely enough with my suggestion, in post #4, that 15mm² cable would be about right.

I had the same problem when I wired in my new fridge, the original wiring was way below spec. I used welding cable that a mate got me

 

[John100156]

Not always the case, often when a neutral is not available a transformer connected to two phases is used to supply the unbalanced load

I was speaking generally but even then a ground path back to the generating source would need to be employed to take the imbalance, are you talking YD? HV/LV?

 

[lw395]

16mmsq cable is going to have about a quarter volt drop. 10a and 10m each way
Depending what voltage the windmill regulates at, that's still enough to seriously slow charging.
The voltage set point of the airbreeze is adjustable from 13.6 to 17Volts, so you could compensate for cable drop, but then you would need some sort of regulation when the batteries were fully charged.
I'd be tempted to whack it up to 17 and have some sort of smart battery charge controller...